Topper Smart Guide-2010 Class-x Science

Chapter: Chemical reactions and equations

Top definitions: 1. Chemical reaction: A chemical reaction involves a chemical change in which substances react to form new substances with entirely new properties. Substances that react or take part in the reaction are known as reactants and the substances formed are known as products. 2. Physical change: If a change involves change in colour or state but no new substance is formed, then it is a physical change. 3. Chemical change: If a change involves formation of new substances, it is a chemical change. 4. Chemical equation: The symbolic representation of a chemical reaction is called a chemical equation. 5. Exothermic and endothermic reactions: If heat is evolved during a reaction, then such a reaction is known as exothermic reaction. If heat is absorbed from the surroundings, then such a reaction is known as endothermic reaction 6. Combination reaction: Combination reaction is a reaction in which 2 or more substances combine to give a single product. 7. Decomposition reaction: In a decomposition reaction, a single reactant decomposes to give 2 or more products. Decomposition reactions require energy in the form of heat, light or electricity 8. Displacement reaction: A reaction in which a more active element displaces less active element from its salt solution. 9. Reactivity series: The Reactivity series is a list of metals arranged in the order of decreasing reactivity. The most reactive metal is placed at the top and the least reactive metal is placed at the bottom. 10.Double displacement reaction: A chemical reaction in which there is an exchange of ions between the reactants to give new substances is called a double displacement reaction. 11.Precipitation reaction: An insoluble solid known as precipitate is formed during a double displacement reaction. Such reactions are also known as precipitation reactions. 12.Redox reaction: A reaction, in which oxidation and reduction takes place simultaneously is known as redox reaction. 13.Oxidation: Oxidation is a chemical process in which a substance gains oxygen or loses hydrogen. 14.Reduction: Reduction is a chemical process in which a substance gains hydrogen or loses oxygen.

Key learnings: 1. A chemical reaction involves a chemical change in which substances react to form new substances with entirely new properties. Substances that react or take part in the reaction are known as reactants and the substances formed are known as products. 2. During a chemical reaction, there is a breaking of bonds between atoms of the reacting molecules to give products. 3. A chemical reaction can be observed with the help of any of the following observations: a) Evolution of a gas b) Change in temperature c) Formation of a precipitate d) Change in colour e) Change of state 4. Physical change: If a change involves change in colour or state but no new substance is formed, then it is a physical change. 5. Chemical change: If a change involves formation of new substances, it is a chemical change. 6. Exothermic and endothermic reactions: If heat is evolved during a reaction, then such a reaction is known as Exothermic reaction. If heat is absorbed from the surroundings, then such a reaction is known as endothermic reaction. 7. Chemical equation: The symbolic representation of a chemical reaction is called a chemical equation. 8. Features of a chemical equation: a. The reactants are written on the left hand side with a plus sign between them. b. The products are written on the right hand side with a plus sign between them. c. An arrow separates the reactants from the products. The arrow head points towards the products and indicates the direction of the reaction. 9. Skeletal chemical equation: A chemical equation which simply represents the symbols and formulae of reactants and products taking part in the reaction is known as skeletal chemical equation for a reaction. For example: For the burning of Magnesium in the air, Mg + O2 → MgO is the skeletal equation. 10. Balanced chemical equation: A balanced equation is a chemical equation in which number of atoms of each element is equal on both sides of the equation i.e. number of atoms of an element on reactant side = number of atoms of that element on the product side.

11. As per the law of conservation of mass, the total mass of the elements present in the products of a chemical reaction is equal to the total mass of the elements present in the reactants. 12. The process of equating the number of atoms on both the sides of a chemical equation is known as balancing of a chemical equation. a. The first step in balancing a chemical equation is to write the number of atoms of each element present on the left hand side and right hand side. b. We should always start balancing with the compound that contains maximum number of atoms. It can be reactant or a product. Then in that compound select the element which has the maximum number of atoms. c.

While balancing a chemical equation, the molecular formulae of the reactants and products should not change. The molecular formulae are simply multiplied by suitable coefficients.

d. To make a chemical equation more informative, the reaction conditions such as temperature, pressure or catalyst are written on the arrow separating the reactants and products. e.

The evolution of gas is indicated by an upward arrow.

f. The formation of precipitate is indicated by a downward arrow. g. Heat evolved during the reaction is written as + Heat on the product side. h. Heat absorbed during the reaction is written as + Heat on the reactant side. 13.Types of chemical reactions: a. Combination reaction b. Decomposition reaction c. Displacement reaction d. Redox reaction 14.Combination reaction is a reaction in which 2 or more substances combine to give a single product. Combination reaction can be between 2 elements, between an element and a compound or between 2 compounds. 15.Decomposition reaction: In a decomposition reaction, a single reactant decomposes to give 2 or more products. Decomposition reactions require energy in the form of heat, light or electricity

16.Types of decomposition reactions: a. Decomposition reactions which require heat are known as thermolytic decomposition reactions b. Decomposition reactions which require light are known as photolytic decomposition reactions c. Decomposition reactions which require electricity are known as electrolytic decomposition reactions 17.Displacement reaction: A reaction in which a more active element displaces less active element from its salt solution. 18.The reactivity series is a list of metals arranged in the order of decreasing reactivity. The most reactive metal is placed at the top and the least reactive metal is placed at the bottom. 19.Double displacement reaction: A chemical reaction in which there is an exchange of ions between the reactants to give new substances is called double displacement reaction. 20.Precipitation reaction: An insoluble solid known as precipitate is formed during a double displacement reaction. Such reactions are also known as precipitation reactions. 21.Redox reaction: A reaction in which oxidation and reduction take place simultaneously in a reaction, is known as a redox reaction. 22.Oxidation is a chemical process in which a substance gains oxygen or loses hydrogen. 23.Reduction is a chemical process in which a substance gains hydrogen or loses oxygen. 24.If a substance gains oxygen or loses hydrogen during a reaction, it is said to be oxidised. 25.If a substance gains hydrogen or loses oxygen during a reaction, it is said to be reduced. 26.A substance that loses oxygen or gains hydrogen is known as an oxidising agent. 27.A substance that loses hydrogen or gains oxygen is known as a reducing agent. 28.An oxidising agent gets reduced whereas a reducing agent gets oxidised. 29. In terms of electronic concept, Oxidation is defined as a loss of electrons while reduction is defined as a gain of electrons. 30. Corrosion is the slow eating up of metals by the action of air and moisture on their surfaces. Corrosion in case of Iron is known as Rusting. 31.Chemically, rust is hydrated ferric oxide (Fe2O3.xH2O) 32.Advantages of corrosion: Though corrosion is undesirable, it can be advantageous in case of aluminium which on exposure to air, gets coated with a protective layer of aluminium oxide. This protects the metal underneath from further corrosion and damage.

33.Rancidity: When oils and fats or foods containing oils and fats are exposed to air, they get oxidised due to which the food becomes stale and gives a bad taste or smell. This is called Rancidity. 34. Rancidity can be prevented by: a) Adding antioxidants i.e. the substances which prevent oxidation b) Refrigeration c) Storing the food in air-tight containers

Chapter : Acids, Bases and Salts

Top concepts: 1. Definition of acids , bases and salts: Acids Sour in taste Give H+ or H3O+ ions in aqueous solutions

Bases Bitter in taste & soapy to touch Give OH- ions in aqueous solutions

Salts Acid + Base → Salt + Water

2. On the basis of origin, acids are classified as: a. Organic acids: Acids derived from living organisms like plants and animals are called organic acids. They are weak acids and are not harmful for living organisms. For example: citric acid is present in fruits, acetic acid present in vinegar, oxalic acid present in tomato, tartaric acid present in tamarind, lactic acid present in sour milk and curd. b. Mineral acids: They are also called inorganic acids. They are dangerous and corrosive. Special precautions have to be taken while handling them. For example: sulphuric acid (H2SO4), hydrochloric acid (HCl) etc. 3. On the basis of their strength, acids are classified as: a. Strong acids: Strong acids are those acids which completely dissociate into its ions in aqueous solutions. Example: nitric acid (HNO3) , sulphuric acid(H2SO4), hydrochloric acid(HCl) b. Weak acids: Weak acids are those acids which do not completely dissociate into its ions in aqueous solutions. For example: carbonic acid (H2CO3), acetic acid (CH3COOH) 4. On the basis of their concentration, acids are classified as: a. Dilute acids: Have a low concentration of acids in aqueous solutions. b. Concentrated acids: Have a high concentration of acids in aqueous solutions. 5. Alkalies: Water soluble bases are called alkalies. For example: Sodium hydroxide (NaOH), potassium hydroxide(KOH)

6. On the basis of their strength, bases are classified as: a. Strong bases: Strong bases are those bases which completely dissociate into its ions in aqueous solutions. Example: sodium hydroxide (NaOH), potassium hydroxide (KOH) b. Weak bases: Weak bases are those bases which do not completely dissociate into its ions in aqueous solutions. For example: ammonium hydroxide (NH4OH) 7. On the basis of their concentration, bases are classified as: a. Dilute bases: Have a low concentration of alkali in aqueous solutions. b. Concentrated bases: Have a high concentration of alkali in aqueous solutions. 8. Acids and bases conduct electricity because they produce ions in water. There is a flow of electric current through the solution by ions. 9. Indicators are those chemical substances which behave differently in acidic and basic medium and help in determining the chemical nature of the substance. Acid base indicators indicate the presence of an acid or a base by a change in their colour or smell.

10.Indicators can be natural or synthetic. 11.Olfactory indicators: These are those indicators whose odour changes in acidic or basic medium. Example: onion

12.Onion: Smell of onion diminishes in a base and remains as it is in an acid. 13.Vanilla essence: The odour of vanilla essence disappears when it is added to a base. The odour of vanilla essence persists when it is added to an acid.

14.Turmeric: In acids, yellow colour of turmeric remains yellow. In bases, yellow colour of turmeric turns red.

15.Litmus: Litmus is a natural indicator. Litmus solution is a purple dye which is extracted from lichen. Acids turn blue litmus red. Bases turn red litmus blue. Water is essential for acids and bases to change the colour of litmus paper. Remember that litmus paper will act as an indicator only if either the litmus paper is moist or the acid or base is

in the form of aqueous solution. This is because acids and bases release H+ and OH- ions respectively in aqueous solutions.

16.Phenolphthalein: Phenolphthalein remains colourless in acids but turn pink in bases. 17.Methyl orange: Methyl orange turns pink in acids and becomes yellow in bases.

18.Reaction of acids and bases with water: Acids Bases + + Release H or H3O ions in water Release OH ions in water H 2O HCl + H2O → H3O+ + ClNaOH(s)  → Na + (aq) + OH − (aq) 19.Reaction of acids and bases with metals: Metals displace hydrogen from the acids and form salt and hydrogen gas. This is a displacement reaction. So, acids react with only those metals which are placed above hydrogen in the reactivity series so that metals can displace hydrogen from acids. Zn + H2SO4 → ZnSO4 + H2 Metal Acid Salt Hydrogen gas Bases react with some metals to form salt and hydrogen gas. Zn + 2 NaOH → Na2ZnO2 + H2 Metal Base Sodium Hydrogen gas zincate (salt) Bases do not react with all the metals to form salt and water. 20.Reaction of acids and bases with metal carbonates: Acids react with metal carbonate to form salt, water and release carbon dioxide.

Na 2 CO3 + 2HCl → 2 NaCl + CO 2 + H 2 O Bases do not react with metal carbonates.

21.Reaction of acids and bases with metal bicarbonates: Acids react with metal bicarbonate to form salt, water and release carbon dioxide.

NaHCO3 + HCl → NaCl + CO 2 + H 2 O Bases do not react with metal bicarbonates. 22. Reaction of acids with bases: Neutralisation reaction: Acids react with bases to form salt and water. HCl + NaOH → NaCl + H2O or H+ +OH- → H2O 23.Reaction of acids with metallic oxides: Metallic oxides are basic. Therefore, acids react with metallic oxides to form salt and water. HCl + CuO → CuCl2 + H2O 24.Reaction of bases with non-metallic oxides: Non – metallic oxides are acidic in nature. Bases react with non- metallic oxides to form salt and water. Example: CO2 Ca(OH)2 + CO2 → CaCO3 + H2O 25.Amphoteric oxides: Oxides which show acidic as well as basic properties. For example: ZnO, Al2O3 HCl + ZnO → ZnCl2 + H2O Zn + 2 NaOH → Na2ZnO2 + H2O 26.Neutral oxides: Oxides which are neither acidic nor basic are called neutral oxides. Example: CO 27.pH: It is used to find out the strength of acids and bases i.e., how strong or weak the acid or a base is. p in pH stands for ‘potenz’ in German. The strength of acids and bases depends on the number of H+ ions and OH- ions produced respectively. 28.pH scale: A scale for measuring hydrogen ion concentration in a solution is called pH scale. 29.On pH scale, we measure pH from 0 to 14. pH value: pH Type of solution Less than 7 Acidic Equal to 7 Neutral More than 7 Basic

30.More the hydrogen ion (or hydronium ion) concentration, lower is the pH value. 31.More the hydroxyl ion concentration, higher is the pH value. 32.Variation in pH:

33. Acids which produce more hydrogen ions are said to be strong acids and acids which produce less hydrogen ions are said to be weak acids. In other words, strong acids have a lower pH value than weak acids. 34. Bases which produce more hydroxyl ions are said to be strong bases and bases which produce less hydroxyl ions are said to be weak bases. In other words, strong bases have a higher pH value than weak bases. 35. Living organisms are pH sensitive. Human body works within a pH range of 7.0 to 7.8. 36. Rain water with a pH less than 5.6 is called acid rain. This acid rain if it flows into river water makes the survival of aquatic life difficult. 37. Plants also require a specific pH range of soil for their healthy growth. 38. pH of our digestive system: Our stomach produces hydrochloric acid for digestion of food. But during indigestion, excess of acid is produced in the stomach and therefore, the pH decreases. This causes pain and irritation. So, to neutralise this excess acid, a mild base is used. This mild base works as an antacid. An antacid is any substance, generally a base or basic salt, which counteracts stomach acidity. 39. Tooth decay: Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel is made up of calcium phosphate which is the hardest substance in the body. It does not dissolve in water, but is corroded when the pH in the mouth is below 5.5. If food particles remain in the mouth after eating, bacteria present in our mouth produce acid by degradation of sugar. This decreases the pH of mouth and hence tooth decay occurs. The best way to prevent this is to clean the mouth after eating food. Using toothpastes, which are generally basic, for cleaning the teeth can neutralise the excess acid and prevent tooth decay.

40. pH is also significant as it is used in self defence by animals and plants. Bees use acids in their sting. To neutralise the effect a mild base like baking soda can be used. 41. Sodium hydroxide (NaOH) Preparation: Chlor Alkali process: In this process, electricity is passed through an aqueous solution of Sodium chloride (called brine). Sodium chloride decomposes to form sodium hydroxide. Chlorine gas is formed at the anode, and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode. 2NaCl(aq) + 2 H2O (l) → 2NaOH(aq) + Cl2(g) + H2(g) 42.Bleaching powder: Bleaching powder is represented as CaOCl2, though the actual composition is quite complex. Preparation: Bleaching powder is produced by the action of chlorine on dry slaked lime. Ca(OH)2 + Cl2 → CaOCl2+ H2O 43.Baking soda: Sodium hydrogen carbonate (NaHCO3) Preparation: NaCl + H2O + CO2+ NH3 → NH4Cl + NaHCO3 44.Washing soda: Sodium carbonate Na2CO3 .10H2O Preparation: In the first step, sodium carbonate is obtained by heating baking soda. Heat

→ Na2CO3 + H2O + CO2 2 NaHCO3  Then washing soda is produced by recrystallisation of sodium carbonate. Na2CO3 + 10H2O → Na2CO3 .10H2O 45.Plaster of Paris: Calcium sulphate hemihydrate CaSO4. ½ H2O Preparation: Plaster of Paris is prepared by heating Gypsum at 373K. CaSO4. 2H2O

Heat at 373K  →

CaSO4. ½ H2O + 1½ H2O

46.Water of crystallisation: It is the fixed number of water molecules present in one formula unit of a salt.

Chapter: Metals and Non – metals

Top concepts:

1. Definition of Metals & Non metals: Metals These are the substances which are electropositive in nature i.e., they have a tendency to lose electrons They generally have 1, 2, or 3 electrons in their outermost shell.

Non - metals These are the substances which are electronegative in nature, i.e. they have a tendency to gain electrons. They generally have 4 to 8 electrons in their outermost shell.

2. Physical properties of Metals and non- metals: Physical Property Metals Non - metals Physical state They are generally They are either solids or solids. gases Exception: Exception: Mercury is a Bromine is a liquid liquid Lustre They have a shiny They do not have a lustre which is called shiny lustre metallic lustre Exception – graphite, iodine Sonorous They generally produce They are non - sonorous a sound on striking a hard surface Malleability Some metals can be Non – metals are not beaten into thin sheets. malleable Most malleable gold and silver Ductility The ability of metals to Non – metals are not be drawn into thin ductile wires is called ductility Gold is the most ductile metal Electrical They are good Non- metals are conductivity conductors of generally poor electricity conductors of electricity Best conductors: Silver Exception: Graphite and copper.

Thermal conductivity

Hardness

Melting point

Densities

They are good conductors of heat Best conductors: Silver and copper. Poor conductors : Lead and mercury They are generally hard Exception – alkali metals like sodium, potassium They generally have high melting points Exception – gallium , alkali metals like sodium, potassium Gallium and caesium will melt if you keep them on your palm They generally have low densities

They are poor conductors of heat

They are generally soft Exception : Diamond is the hardest substance known They generally have low melting points

They generally have high densities

3. The elements which have intermediate properties between those of metals and non-metals are called metalloids. 4. Allotropes are two or more different forms of the same element. 5. Reaction of metals with oxygen: Almost all metals combine with oxygen to form metal oxides. But all metals do not react with oxygen at the same rate. Different metals show different reactivities towards oxygen. Metal oxides are basic in nature. But some metal oxides are amphoteric oxides. 6. Most metal oxides are insoluble in water but some of these dissolve in water to form alkalies. Example: Na2O (s) + H2O (l) → 2 NaOH (aq)

7.

Amphoteric oxides: Metal oxides which show both acidic as well as basic behaviour are known as amphoteric oxides. Such metal oxides which react with both acids as well as bases to produce salts and

water. For example: aluminium oxide, zinc oxide, etc. Al2O3 + 6 HCl → 2 AlCl3 + 3 H2O Al2O3 + 2 NaOH → 2 NaAlO2 + H2O

8. Reaction of metals with water: Metal Potassium Sodium Calcium Magnesium Aluminium Iron Zinc Lead Silver Gold Copper

Reacts with Violently with cold water Violently with cold water Less violently with cold water Hot water Steam Steam Steam No reaction at all No reaction at all No reaction at all No reaction at all

Products KOH, H2 NaOH, H2 Ca(OH)2, H2 Mg(OH)2, H2 Al2O3, H2 Fe3O4, H2 ZnO, H2

9. Reaction of metals with acids: Metal + Dilute acid → Salt + Hydrogen 10. Reaction of metals with nitric acid: Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because HNO3 is a strong oxidising agent. It oxidises the H2 produced to water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2). But magnesium (Mg) and manganese (Mn) react with very dilute HNO3 to evolve H2 gas. 11. Aqua regia: Aqua regia is a freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. 12. Anodising: It is a process of forming a thick oxide layer of aluminium. During anodising, a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid. The oxygen gas evolved at the anode reacts with aluminium to make a thicker protective oxide layer. This aluminium oxide coat makes it resistant to further corrosion.

13. Reaction of metals with solution of other metal salts: Metal A + Salt solution of B → Salt solution of A + Metal B (Metal A is more reactive than metal B) 14. Reactivity series: The reactivity series is a list of metals arranged in the order of their decreasing activities.

15. Reaction of metals with non – metals: When a metal and a non- metal react with each other, transfer of electrons take place from metal to nonmetal.. 16. Ionic compounds: The compounds thus formed by complete transference of electrons from a metal to non- metal are known as ionic compounds. Ionic compounds have strong electrostatic force of attraction between the positive and negative ions. 17. Properties of ionic compounds: a. Physical nature: Ionic compounds are solids and are somewhat hard. b. Melting and Boiling points: Ionic compounds have high melting and boiling points c. Solubility: Electrovalent compounds are generally soluble in water and insoluble in solvents such as kerosene, petrol, etc. d. Conduction of Electricity: Ionic compounds do not conduct electricity in the solid state but conduct electricity in the molten state or when dissolved in water.

18. Corrosion: The process of slowly eating away of the metal due to attack of air, water, etc., on the surface of the metal is called corrosion. 19. The rusting of iron can be prevented by painting, oiling, greasing, galvanising, chrome plating, anodising or making alloys.

20. Galvanisation is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc. The galvanised article is protected against rusting even if the zinc coating is broken.

21. Alloys: An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. 22. Alloys and their constituents: Alloy Brass Bronze Steel Stainless steel Solder

Constituents Copper, zinc Copper, tin Iron, carbon Iron, nickel, chromium Lead, tin

23. Mineral: The elements or compounds, which occur naturally in the earth’s crust, are known as minerals. 24. Ore: The minerals contain a very high percentage of a particular metal and from which the metal can be profitably extracted is called ore. 25. Gangue: The unwanted materials or impurities present in the ores is called gangue. 26. Enrichment of ore: Ores mined from the earth are usually contaminated with gangue. The removal of gangue from the ore is called enrichment of ore. The process used for enrichment of ores is based on the differences between the physical or chemical properties of the gangue and the ore.

27. Steps involved in the extraction of metals from ores:

28. Metals low in the activity series: Metals low in the activity series are very unreactive. The oxides of these metals can be reduced to metals by heating alone. 29. Metals in the middle of the activity series: The metals in the middle of the activity series are moderately reactive. These are usually present as sulphides or carbonates in nature. They are first converted to metal oxides and then in the next step the metal oxides are reduced to metal.

31. Conversion of ore into oxide form: It can be done in two ways: Roasting The process of heating the sulphide ore in the presence of sufficient supply of air to convert it into oxide is called roasting. This process is used for sulphide ores. Example: Heat 2 ZnS (s) + 3O2 (g)  → 2ZnO (s) +2SO2 (g)

Calcination The process of heating the carbonate ore in the presence of limited supply of air to convert it into oxide is called calcination. This process is used for carbonate ores. Example: Heat ZnCO3 (s)  → ZnO (s) + CO2 (g)

32. Metals towards the top of the reactivity series: These are highly reactive metals. Example: Sodium, calcium, magnesium, aluminium are obtained by electrolysis of molten chlorides. These metals are obtained by electrolytic reduction. 33. Electrolytic reduction of molten sodium chloride: At cathode: Na+ + e– → Na At anode: 2Cl– → Cl2 + 2e– 34. Electrolytic refining of metal: At anode: M → Mn+ + n e– (Impure metal) At cathode: Mn+ + n e– → M (Pure metal)

Chapter : Carbon and its compounds

Top concepts: 1. Covalent bond: A covalent bond is a bond formed by sharing of electrons between atoms. In a covalent bond, the shared pair of electrons belongs to the valence shell of both the atoms. 2. Conditions for formation of covalent bond: a. The combining atoms should have 4 to 7 electrons in their valence shell. b. The combining atoms should not lose electrons easily. c. The combining atoms should gain electrons readily. d. The difference in electronegativities of two bonded atoms should be low. 3. Properties of covalent compounds: a. Physical states: They are generally liquids or gases. Some covalent compounds may exist as solids. b. Solubility: They are generally insoluble in water and other polar solvents but soluble in organic solvents like benzene, toluene etc. c. Melting and boiling point: They generally have low melting and boiling points. d. Electrical conductivity: They do not conduct electrical current. 4. Steps for writing the Lewis dot structures of covalent compounds: a. Write the electronic configuration of all the atoms present in the molecule. b. Identify how many electrons are needed by each atom to attain noble gas configuration. c. Share the electrons between atoms in such a way that all the atoms in a molecule have noble gas configuration. d. Keep in mind that the shared electrons are counted in the valence shell of both the atoms sharing it.

5. Electronic configuration of some non- metals: Name of element Hydrogen Carbon Nitrogen Oxygen Fluorine Phosphorus Sulphur Chlorine Argon

Sy mb ol H C N O K P S Cl Ar

Ato mic No. 1 6 7 8 9 15 16 17 18

Elec tron s 1 6 7 8 9 15 16 17 18

Distribution of electrons

Valen cy

1 2, 2, 2, 2, 2, 2, 2, 2,

1 4 3 2 1 3 2 1 0

4 5 6 7 8, 8, 8, 8,

5 6 7 8

Type of element Non – metal Non – metal Non – metal Non – metal Non – metal Non – metal Non – metal Non – metal Noble gas

6. Carbon forms covalent bonds. 7. Electronegativity – It is the ability of an atom to attract a shared pair of electrons towards itself. 8. If the atoms forming a covalent bond have different electronegativities, the atom with higher electronegativity pulls the shared pair of electron towards itself. Thus, the atom with the higher electronegativity develops a partial negative charge and the atom with the lower electronegativity develops a partial positive charge. This covalent bond with some polarity is called polar covalent bond. 9. Carbon forms a large number of compounds because of two unique properties: a. Tetravalency b. Catenation 10.Tetravalency of carbon: Atomic number = 6 Electronic configuration: 2, 4 Valence electrons = 4 Valency = 4 So, carbon needs four electrons to attain noble gas configuration. Or in other words, carbon has the ability to form four bonds with carbon or atoms of other mono-valent elements. 11.Catenation: Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called catenation.

12.Steps for writing the Lewis dot structures of Hydrocarbons: a. Write the electronic configuration of all the atoms present in the molecule. b. Identify how many electrons are needed by each atom to attain noble gas configuration. c. First complete the noble gas configuration of all the hydrogen atoms by bonding each hydrogen atom with a carbon atom by a single bond. d. The remaining valency of each carbon is completed by forming carbon – carbon single, double or triple bonds. e. Keep in mind that the shared electrons are counted in the valence shell of both the atoms sharing it. 13.Classification of hydrocarbons:

a. Aliphatic or open chain hydrocarbons: These are the carbon compounds which have carbon carbon long open chains. They are classified as: i. Saturated hydrocarbons: These hydrocarbons have all carbon – carbon single bonds. ii. Unsaturated hydrocarbons: These hydrocarbons have at least one carbon – carbon double or triple bonds. • Hydrocarbons with at least one carbon-carbon double bond are called alkenes. General formula = CnH2n where n = number of carbon atoms • Hydrocarbons with at least one carbon-carbon triple bond are called alkynes. General formula = CnH2n-2 where n = number of carbon atoms

b. Cyclic or closed chain hydrocarbons: These are the hydrocarbons which have carbon carbon closed chain. They are classified as: i. Alicyclic hydrocarbons: These are the hydrocarbons which do not have benzene ring in their structure. ii. Aromatic hydrocarbons: These are the hydrocarbons which have benzene ring in their structure. When hydrogen bonded to carbon of benzene is substituted with halogens, radicals or other functional groups, the derivatives are called aromatic compounds. 14.Benzene: It is an aromatic hydrocarbon which has the molecular formula C6H6. It has alternating carbon - carbon single and double bonds.

Benzene can also be represented as:

15.IUPAC name of hydrocarbon consists of two parts: a. Word root: Number of carbons in the longest carbon chain Number of carbon atoms 1 2 3 4 5 6 7 8 9 10

Word root (Greek name) Meth Eth Prop But Pent Hex Hept Oct Non Dec

b. Suffix: Depends on the type of carbon – carbon bond: for single bond, suffix is –ane ; for double bond, suffix is –ene, and for triple bond suffix is –yne 16.Steps to write the IUPAC nomenclature of hydrocarbons: a. Select the parent carbon chain: i. Select the longest carbon chain as the parent chain. ii. If a double or a triple bond is present in the carbon chain, it should be included in the parent chain. b. Number the parent carbon chain from that carbon end such that the double bond, triple bond or side chain gets the lowest number. c. Identify and name the side chain if any: -CH3 is named as methyl, -C2H5 is named as ethyl etc. Also identify the position of the side chain. d. Write the name of the hydrocarbon as: Position number-name of the side chain word root – Position number- suffix Example: 2-Methyl but-1-ene e. Remember if the hydrocarbon is an alkane, the position number of suffix is not written. 17.Types of formula for writing hydrocarbons: a. Molecular formula: The actual number of each type of atom present in the compound. b. Structural formula: The actual arrangement of atoms is written c. Condensed formula: It is the shortened form of the structural formula

18.Conditions for Isomerism: a. Only alkanes with more than three carbon atoms can have isomers. b. The side chains cannot be present on the terminal carbons. 19. How to write different chain isomers of hydrocarbons: a. First draw the different carbon chains keeping in mind the conditions for isomerism. b. Complete the tetravalency of carbon by forming single covalent bonds with hydrogens. c. In the end, check that the molecular formula of each isomer should be same. 20. How to write different position isomers of unsaturated hydrocarbons: a. First draw the different carbon chains keeping in mind the conditions for isomerism.

b. If it is an alkene draw the first isomer always by drawing a double bond between C1 and C2 or if it is an alkyne draw the first isomer always by drawing a triple bond between C1 and C2 c. The next isomers will be dawn by drawing the same chain and changing the positions of the double and triple bonds in alkenes and alkynes respectively. d. Complete the tetravalency of carbon by forming single covalent bonds with hydrogens. e. In the end, check that the molecular formula of each isomer should be same. 21.Homologous Series: A series of organic compounds in which every succeeding member differs from the previous one by –CH2 or 14 u. The molecular formula of all the members of a homologous series can be derived from a general formula. 22.Properties of a homologous series: As the molecular mass increases in a series, so physical properties of the compounds show a variation, but chemical properties which are determined by a functional group remain the same within a series. 23.Homologous series of alkanes: General formula: CnH2n+2 where n = number of carbon atoms

24. Homologous series of alkenes: General formula: CnH2n where n = number of carbon atoms 25.Homologous series of alkynes: General formula: = CnH2n-2 where n = number of carbon atoms 26.Functional group: An atom or a group of atoms which when present in a compound gives specific properties to it, regardless of the length and nature of the carbon chain is called functional group. a. Free valency or valencies of the group are shown by the single line. b. The functional group is attached to the carbon chain through this valency by replacing one hydrogen atom or atoms. c. Replacement of hydrogen atom by a functional group is always in such a manner that valency of carbon remains satisfied. d. The functional group, replacing the hydrogen is also called as hetero atom because it is different from carbon, and can be nitrogen, sulphur, or halogen etc.

27.Some functional groups in carbon compounds: Heteroatom

Cl/ Br

Oxygen

Functional group

Formula of the functional group

Halo-

Suffix

Named as prefix

Chloro

-Cl

Chloro –

Bromo Alcohol

-Br -OH

Bromo - ol

Aldehyde

-al

Ketone

-one

Carboxylic acid

-oic acid

28.

Steps to write the IUPAC name of organic compounds: i. Select the parent carbon chain: 1. Select the longest carbon chain as the parent chain. 2. If a double or a triple bond is present in the carbon chain, it should be included in the parent chain. 3. If a functional group is present, the carbon chain should include the functional group. ii. Number the parent carbon chain from that carbon end such that the functional group, double bond, triple bond or side chain gets the lowest number. Remember here that the aldehyde and carboxylic acid functional group are present on the terminal carbon atom. iii. Identify the name and position of the functional group, double bond, triple bond or side chain. iv. The name of the functional group is written with either a prefix or a suffix as given in the above table. v. If the name of the functional group is to be given as a suffix, the name of the carbon chain is modified by deleting the final ‘e’ and adding the appropriate suffix. For example, a three-carbon chain with a ketone group would

be named in the following manner – Propane – ‘e’ = propan + ‘one’ = propanone. vi. Remember that in the compounds which have carbon containing functional groups, the name of the word root includes the functional group carbon atom also. vii. If the carbon chain is unsaturated, then the final ‘ane’ in the name of the carbon chain is substituted by ‘ene’ or ‘yne’ as given in the table above. For example, a threecarbon chain with a double bond would be called propene and if it has a triple bond, it would be called propyne.

29. Difference between chemical properties of saturated and unsaturated hydrocarbons: Saturated hydrocarbons Give a clean blue flame on complete combustion and on incomplete combustion give a yellow sooty flame. Undergo substitution reaction like chlorination Are fairly unreactive and inert in the presence of most reagents

Unsaturated hydrocarbons Give a yellow sooty flame on combustion.

Undergo addition reaction like hydrogenation, addition reaction with bromine in carbon tetrachloride Are reactive

30.Catalysts are substances that cause a reaction to occur or proceed at a different rate without the reaction being affected. 31.Oxidizing agents are substances which are capable of providing oxygen to other compounds for their oxygen. Example: Alkaline KMnO4, acidified K2Cr2O7 etc. 32.Reactions of ethanol: 2 CH3CH2OH + 2 Na → 2 CH3CH2ONa + H2 Hot conc. H SO

2 4 → CH =CH + H O 2 CH3CH2OH  2 2 2 Alkaline KMnO

+ Heat

4 2 CH3CH2OH  → CH3COOH Or acidifiedK Cr O + Heat 2 2 7

33.Reactions of ethanoic acid: CH3COOH + NaOH → CH3COONa + H2O acid CH3COOH +CH3CH2OH  → CH3COO CH2CH3 ester → CH3COONa+ C2H5OH CH3COO C2H5 + NaOH  CH3COOH +NaOH  → CH3COONa + H2O 2 CH3COOH +Na2CO3  → 2 CH3COONa + H2O + CO2 CH3COOH +NaHCO3  → CH3COONa + H2O + CO2

34. Catalysts are substances that cause a reaction to occur or proceed at a different rate without the reaction being affected. 35.Soaps are sodium or potassium salts of long chain carboxylic acids. 36. Structure of soap molecule: The structure of soap molecule consists of a long hydrocarbon tail at one end which is hydrophobic in nature. The other end is the ionic part which is hydrophilic in nature.

37.Cleansing action of soap: When soap is at the surface of water, the ionic end of soap orients itself towards water and the hydrocarbon ‘tail’ orients itself aligns itself along the dirt. Thus, clusters of molecules are formed in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle.

Soap in the form of a micelle is able to clean, since the oily dirt will be collected in the centre of the micelle. The micelles stay in solution as a colloid and will not come together to precipitate because of ion-ion repulsion. Now, when water is agitated, the dirt suspended in the micelles is also easily rinsed away. 38.When hard water is treated with soap, scum is formed. This is caused by the reaction of soap with the calcium and magnesium salts, which cause the hardness of water.

39.Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids. 40.Detergents do not form scum with hard water. This is because the charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in hard water. Thus, they remain effective in hard water. 41. Soaps Soaps are sodium or potassium salts of long chain carboxylic acids.

Soaps are not effective for cleaning in hard water. Soaps are biodegradable.

Detergents Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids. Detergents are effective for cleaning in hard as well as soft water. Detergents are non biodegradable.

Chapter: Periodic classification of elements

Top concepts

1. Dobereiner’s triads: Johann Wolfgang Dobereiner, a German chemist, classified the known elements in groups of three elements on the basis of similarities in their properties. These groups were called triads. •

Characteristic of Dobereiner’s Triads:

a. Properties of elements in each triad were similar. b. Atomic mass of the middle elements was roughly the average of the atomic masses of the other two elements. Example of Dobereiner’s Triads : Atomic Element Element mass

Atomic mass

Lithium (Li)

6.9

Calcium (Ca)

40.1

Sodium (Na)

23.0

Strontium (Sr)

87.6

Potassium (K)

39.0

Barium (Ba)

137.3

•

Element Chlorine (Cl) Bromine (Br) Iodine (I)

Atomic mass 35.5 79.9 126.9

• Limitations: Dobereiner could identify only three triads. He was not able to prepare triads of all the known elements

2. Newlands’ Law of Octaves: John Newlands, an English scientist, arranged the known elements in the order of increasing atomic masses and called it the ‘Law of Octaves’. It is known as ‘Newlands’ Law of Octaves’ •

Characteristics of Newlands’ Law of Octaves

a. It contained the elements from hydrogen to thorium b. Properties of every eighth element were similar to that of the first element

• Table sa (do) H F Cl Co and Ni Br

•

showing Newlands’ Octaves: re ga ma (re) (mi) (fa) Li Be B Na Mg Al K Ca Cr Cu Zn Y

pa (so) C Si Ti In

da (la) N P Mn As

ni (ti) O S Fe Se

Rb

Zr

-

-

Sr

Ce and La

Limitations of Newlands’ law of Octaves:

a. The law was applicable to elements upto calcium (Ca) only b. It contained only 56 elements. Further it was assumed by Newlands that only 56 elements existed in nature and no more elements would be discovered in the future. c. In order to fit elements into the table. Newlands’ adjusted two elements in the same slot and also put some unlike elements under same note. For example cobalt and nickel are in the same slot and these are placed in the same column as fluorine, chlorine and bromine which have very different properties than these elements. Iron, which resembles cobalt and nickel in properties, has been placed differently away from these elements 3. Mendeleev’s Periodic Table: Dmitri Ivanovich Mendeleev, a Russian chemist, was the most important contributor to the early development of a periodic table of elements wherein the elements were arranged on the basis of their atomic mass and chemical properties.. •

Characteristic of Mendeleev’s Period Table:

a. Mendeleev arranged all the 63 known elements in an increasing order of their atomic masses. b. The table contained vertical columns called ‘groups’ and horizontal rows called ‘periods’. c. The elements with similar physical and chemical properties came under same groups. • Mendeleev’s Periodic Law: The properties of elements are the periodic function of their atomic masses.

•

Achievements of Mendeleev’s Periodic Table:

a. Through this table, it was very easy to study the physical and chemical properties of various elements. b. Mendeleev adjusted few elements with a slightly greater atomic mass before the elements with slightly lower atomic mass, so that elements with similar properties could be grouped together. For example, aluminum appeared before silicon, cobalt appeared before nickel. c. Mendeleev left some gaps in his periodic table. He predicted the existence of some elements that had not been discovered at that time. His predictions were quite true as elements like scandium; gallium and germanium were discovered later d. The gases like helium, neon and argon, which were discovered later, were placed in a new group without disturbing the existing order •

Limitations of Mendeleev’s Periodic Table :

a. He could not assign a correct position to hydrogen in the periodic table b. Positions of isotopes of all elements was not certain according to Mendeleev’s periodic table c. Atomic masses did not increase in a regular manner in going from one element to the next. So it was not possible to predict how many elements could be discovered between two elements 4. Modern Periodic Table: Henry Moseley gave a new property of elements, ‘atomic number’ and this was adopted as the basis of Modern Periodic Table’. • Modern Periodic Law: Properties of elements are a periodic function of their atomic number •

Position of elements in Modern Periodic Table: a. The modern periodic table consists of 18 groups and 7 periods

b. Elements present in any one group have the same number of valence electrons. Also, the number of shells increases as we go down the group. c. Elements present in any one period, contain the same number of shells. Also, with increase in atomic number by one unit on moving from left to right, the valence shell electron increases by one unit d. Each period marks a new electronic shell getting filled

•

Trends in the Modern Periodic Table:

(i) Valency: Valency of an element is determined by the number of valence electrons present in the outermost shell of its atom •

Valency of elements in a particular group is same

• Valency of elements in a particular period increases by one unit from left to right with the increase in atomic number by one unit (ii)

Atomic Size: Atomic size refers to the radius of an atom.

• In a period, atomic size and radii decreases from left to right. This is due to increase in nuclear charge which tends to pull the electrons closer to nucleus and reduces size of atom • In a group, atomic size and radii increases from top to bottom. This is because on moving down, new shells are added. This increases distance between outermost electrons and nucleus which increases the size of atom (iii)

Metallic and Non- metallic Properties:

• The tendency to lose electrons from the outermost shell of an atom, is called metallic character of an element • Metallic character decreases across a period and increases down the group • The tendency to gain electron in the outermost shell of an atom, is called non- metallic character of an element • Non-metallic character increases across a period and decreases down the group • Elements intermediate between metal and non-metals that show characteristic of both metals and non-metals are called as semi-metals or metalloids 5. Metals have a tendency to loose electrons while forming bond. Hence they are electropositive in nature 6. Non-metals have a tendency to gain electrons while forming bond. Hence they are electronegative in nature 7. Oxides formed by metals are generally basic and oxides formed by nonmetals are generally acidic

Ch: Life Processes.

Key learnings:

1) The ability to perform the basic life processes distinguishes a living organism from a non-living one.

2) Life processes are the vital processes carried out by living organisms in order to maintain and sustain life. Molecular movements are essential to carry out the various life processes.

3) Specialised body parts perform the various life processes in multicellular organisms. No such organs are present in unicellular organisms.

4) Energy required to carry out the different life processes, is obtained from carbon-based food sources through nutrition.

5) Depending on the mode of obtaining nutrition, organisms are classified as autotrophs or heterotrophs. i) Autotrophs can prepare their own food from simple inorganic sources like carbon dioxide and water. (eg- green plants, some bacteria) ii) Heterotrophs cannot synthesize their own food and is dependent on the autotrophs for obtaining complex organic substances for nutrition. (eg. – animals)

6) Green plants prepare their food by the process of photosynthesis. Here, they utilize CO2, H2O and sunlight, with the help of chlorophyll, giving out O2 as a byproduct.

7) In the light reaction of photosynthesis, light energy is absorbed and converted to chemical energy in the form of ATP. Also water molecules are split into hydrogen and oxygen.

8) Carbon dioxide is reduced to carbohydrates in the dark phase of photosynthesis.

9) Plants carry out gaseous exchange with surrounding through stomata.

10) Heterotrophs may be herbivores, carnivores, parasites or saprophytes.

11) In Amoeba, digestion occurs in the food vacuole, formed by the engulfing of food by its pseudopodia.

12) In humans, digestion of food takes place in the alimentary canal, made up of various organs and glands.

13) In mouth, food is crushed into small particles through chewing and mixed with saliva, which contains amylase for digesting starch.

14) On swallowing, food passes through pharynx and oesophagus to reach stomach. The gastric juice contains pepsin (for digesting proteins), HCl and mucus.

15) Liver secretes bile which emulsifies fat.

16) Pancreatic juice contains enzymes amylase, trypsin and lipase for digesting starch, proteins and fats respectively.

17) In the small intestine, carbohydrates, proteins and fats are completely digested into glucose, amino acids, and fatty acids and glycerol respectively.

18) The villi of small intestine absorb the digested food and supply it to every cell of the body.

19) The undigested food is egested from the body through anus.

20) During respiration, the digested food materials are broken down to release energy in the form of ATP.

22) Depending on the requirement of oxygen, respiration may be i) Aerobic - occurring in presence of oxygen or ii) Anaerobic – occurring in absence of oxygen.

23) The end-products are lactic acid or ethanol + CO2, in anaerobic respiration or CO2 and water in aerobic respiration. Large amount of energy is released in aerobic respiration as compared to anaerobic respiration.

24) Plants release CO2 at night and oxygen during the day.

25) Terrestrial organisms use atmospheric oxygen for respiration whereas aquatic organisms use the dissolved oxygen in water.

26) In humans, air takes the following path on entering the nostrils. Nostrils
Nasal passage
Pharynx
Larynx
Trachea
Bronchus
Bronchiole
Alveolus.

27) The alveoli of lungs are richly supplied with blood and are the sites where exchange of gases (O2 and CO2) occurs between blood and atmosphere.

28) In humans, the respiratory pigment haemoglobin, carry oxygen from lungs to different tissues of the body.

30) In humans, the circulatory system transports various materials throughout the body and is composed of the heart, blood and blood vessels.

31) Human heart has 4 chambers – 2 atria (right and left) and 2 ventricles (right and left). Right half of the heart receives deoxygenated blood whereas the left half receives oxygenated blood.

32) Ventricular walls are much thicker than atrial walls.

33) Arteries carry blood from heart to different parts of the body whereas veins deliver the blood back to the heart. Arteries are connected to veins by thin capillaries, wherein materials are exchanged between blood and cells.

34) Humans show double circulation and complete separation of oxygenated and deoxygenated blood.

35) Blood platelets are essential for clotting of blood at the place of injury and thus preventing blood loss.

36) Lymphatic system consists of lymph, lymph nodes, lymphatic capillaries and lymph vessels which drain into larger veins. Lymph is also important in the process of transportation.

37) In plants, water is transported through the xylem tissue, from roots to the aerial parts of the plant. Root pressure and transpiration pull are the major forces involved in pulling water up the xylem.

38) Translocation of food is carried out through phloem tissue from leaves and storage organs to other parts of the plant. This process requires energy from ATP.

39) During excretion, the harmful metabolic nitrogenous wastes generated are removed from the body.

40) In humans, a pair of kidneys, a pair of ureters, urinary bladder and urethra constitutes the excretory system.

41) Nephrons are the basic filtration units of kidneys. They carry out filtration, selective reabsorption and tubular secretion to form urine in kidney, which is then passed out through the urethra, via the ureters and urinary bladder.

42) Plants do not have an excretory system and carries out excretion in various ways like transpiration, releasing wastes into surrounding soil, losing the leaves and storing in cell vacuoles and in old xylem.

Top definitions

1) Life processes - The vital processes carried out by living organisms in order to maintain and sustain life.

2) Nutrition - The process of obtaining and utilizing the nutrients necessary to sustain life.

3) Autotrophic nutrition - Nutrition characterized by the ability to use simple inorganic substances for the synthesis of more complex organic compounds, as in green plants and some bacteria

4) Autotroph - An organism capable of synthesizing its own food from simple inorganic substances, using light or chemical energy.

5) Heterotrophic nutrition – A type of nutrition in which energy is derived from the intake and digestion of organic substances, normally plant or animal tissues

6) Heterotrophs – An organism that cannot synthesize its own food and is dependent on complex organic substances for nutrition

7) Photosynthesis – The process by which plants and other organisms generate carbohydrates and oxygen from carbon dioxide and water using light energy, with the help of chlorophyll.

8) Stomata – The minute pores present in the epidermis of a leaf or stem through which gaseous exchange and transpiration occur.

9) Alimentary canal – A long tube extending from the mouth to the anus that has regions specialized for ingestion, digestion, absorption, and egestion.

10) Enzymes – The biological catalysts which speed up the rate of biochemical reactions in the body.

11) Peristalsis – The process of wave-like contractions and relaxations of the alimentary tract that propels the food forward through the tract.

12) Gastric glands – The glands present in the wall of the stomach that release HCl, pepsin and mucus.

13) Pepsin – A digestive enzyme found in gastric juice that catalyzes the breakdown of proteins to peptides.

14) Emulsification of fat – A process in which bile salts emulsifies fat globules, i.e. increases the surface area of the oil–water interface, which promotes the breakdown of fats by pancreatic lipase.

15) Bile – A digestive juice secreted by the liver, stored in the gallbladder and aids in the digestion of fats.

16) Pancreatic juice - A clear alkaline secretion of the pancreas containing enzymes that aid in the digestion of proteins, carbohydrates, and fats.

17) Trypsin – A pancreatic enzyme that catalyzes the breakdown of proteins into smaller units.

18) Lipase – An enzyme that catalyze the breakdown of fats into fatty acids and glycerol.

19) Intestinal juice – The digestive fluid secreted by the glands lining the walls of the small intestine.

20) Villi – The numerous projections arising from the inner lining of the small intestine, which increase the surface area for absorption.

21) Egestion – The elimination of the waste and undigested matter from the digestive tract through the anus.

22) Respiration – The process by which food is burned by living cells to release energy in the form of ATP, for various body purposes.

23) Aerobic respiration – The metabolic process that uses oxygen to break down food and produce carbon dioxide and water, along with the release of energy.

24) Anaerobic respiration – The metabolic process by which nutrients are broken down in the absence of oxygen to release energy.

25) Alveoli – The tiny air sacs of the lungs where gas exchange occurs with the circulatory system.

26) Trachea – A thin walled tube of the respiratory system with cartilaginous rings that conveys inhaled air from the larynx to the bronchi.

27) Bronchus – Either of the two main branches of the trachea, which delivers air to the lungs from trachea.

28) Haemoglobin – The respiratory pigment present in the red blood cells of vertebrates, which transports oxygen from lungs to the tissues.

29) Blood plasma – The fluid portion of the blood in which the blood cells are normally suspended.

30) Atria – The two upper chambers in the heart, which receive blood from the veins and push it into the ventricles.

31) Ventricles – The two lower chambers of the heart, which receive blood from the atria and pump it into the arteries.

32) Double circulation – A type of circulation in which the blood flows through the heart twice, during each cycle of passage through the body.

33) Arteries – The blood vessels which carry blood away from the heart to various organs of the body.

34) Veins – The blood vessels which collect blood from different organs of the body and bring it back to the heart.

35) Blood clotting – The process by which the blood coagulates to form solid masses, or clots so as to prevent blood loss during injury.

36) Blood clot - A semisolid gelatinous mass of coagulated blood that consists of red blood cells, white blood cells, and platelets entrapped in a fibrin network.

37) Root pressure – Pressure exerted in the roots of plants as the result of osmosis that causes sap to rise through a plant stem to the leaves.

38) Transpiration – The loss of water vapour from the aerial parts of the plant.

39) Translocation – The transport of soluble products of photosynthesis from leaves or storage organs to other parts of the plant through phloem.

40) Excretion – The biological process by which the harmful metabolic wastes are removed from the body.

41) Kidney – Either of the two bean-shaped excretory organs that filter wastes (especially urea) from the blood and excrete them and water in urine.

42) Nephron – The basic filtration unit in the kidneys, which removes waste products from the blood and forms urine.

Top Reactions

1)

Chlorophyll 6CO2 + 6H2O → C6H12O6 + 6O2 Sunlight Glu cos e

2)

Top diagrams 1.

2.

3.

4.

5.

6.

7.

8.

9.

Chapter : Control and coordination. Key Learnings

1) A system of control and coordination is essential in living organisms so that the different body parts can function as a single unit to maintain homeostasis as well as respond to various stimuli.

2) In animals, the nervous system and hormonal system are responsible for control and coordination.

3) Neurons are specialized cells of the nervous system. They use electrical and chemical signals for transferring information.

4) Receptors are specialized tips of the nerve fibres that collect the information to be conducted by the nerves.

5) Nerve impulses travel in the following manner from one neuron to the next

: Dendrites


tip of axon


Cell body
Axon


Nerve endings at the

Synapse
Dendrite of next neuron.

6) Chemicals released from axon tip of one neuron, cross the synapse or neuromuscular junction to reach the next cell (neuron or muscle fibre).

7) Nerve impulses from many neurons interact to carry out the complex process of thinking.

8) Central nervous system and peripheral nervous system are parts of our nervous system.

9) Central nervous system is made up of the brain and spinal cord.

10)

Spinal cord controls the reflex actions and conducts messages

between different parts of the body and brain.

11)

Reflex action is an automatic, rapid and immediate reaction to a

stimulus and is below the level of consciousness. No thinking is involved in reflex action.

12)

Reflex arc is the neural pathway that mediates a reflex action.

Pathway of reflex arc : Receptor
Sensory neuron
Relay neuron
Motor neuron
Effector 13)

The sensory neurons of reflex arcs synapse in the spinal cord

which then activates the spinal motor neurons without delay to execute a quick action, especially in case of emergencies. The brain also receives the information while the reflex action occurs.

14)

The 3 main parts of the brain are forebrain, midbrain and

hindbrain.

15)

The largest part of the brain, the forebrain, is the main thinking

region. It is made up of cerebrum, hypothalamus and thalamus. Cerebellum, pons and medulla constitute the hindbrain.

16)

Cerebrum is the largest part of the brain whereas the

cerebellum is the second largest part.

17) Part of brain

Function

Cerebrum

Governs intelligence, thinking, memory and other mental abilities, voluntary actions, sensations, emotions and speech

Hypothalamus

Thalamus

Coordinates messages from the autonomous nervous system, controls certain involuntary actions, as well as the sexual and emotional behaviour and forms an axis with the pituitary Functions as major coordinating center for sensory and motor signaling.

Midbrain

Acts as the coordinating centre between forebrain and hindbrain; also controls certain involuntary movements

Cerebellum

Responsible for precision and fine control of voluntary movements as well as maintaining posture and equilibrium of the body

Pons

Relays impulses between the lower cerebellum and spinal cord, and higher parts of the brain like the cerebrum and mid brain; also regulates respiration

Medulla

Contains vital centres for controlling blood pressure, respiration, swallowing, salivation, vomiting, sneezing and coughing.

18)

Brain is protected by a bony box called cranium, within which

are present 3 layers of fluid-filled membranes for absorbing shock. 19)

Peripheral nervous system consists of cranial nerves and spinal

nerves and assists in transmitting information between central nervous system and rest of the body.

20)

Reflex actions, voluntary actions and involuntary actions are the

various types of responses shown by the nervous system.

21)

The sense organs detect changes in surroundings and pass this

information to the central nervous system, which after processing the information, acts through the muscles.

22)

`The movements of muscle tissues are brought about by the

contraction and relaxation of the contractile proteins in response to nerve impulses.

23)

Plants lack nervous and muscular system.

24)

Plants respond to stimuli by showing 2 types of movements –

growth independent and growth dependent.

25)

Growth independent movements are usually quicker than

growth dependent ones, and involve the use of electrochemical signals by the plant. To achieve this movement, the plant cells change shape by altering their water content.

26)

Growth dependent movements or tropic movements are slow,

occurring either towards or away from the stimulus.

27)

Tropic movements are shown in response to environmental

factors such as light, gravity, water and chemicals.

28)

Plant roots are positively geotropic and negatively phototropic

whereas plant shoots are usually negatively geotropic and positively phototropic.

29)

Pollen tubes show chemotropism by growing towards the ovules.

30)

In addition to electrochemical signals, plants and animals use

hormones for control and coordination.

31)

Important plant hormones are auxin, gibberellin, cytokinin,

abscisic acid and ethylene.

Plant hormone Function Auxin

Cell elongation

Cytokinin

Cell division

Gibberellin

Growth of stem

Abscisic acid

Inhibits growth

Ethylene

Ripening of fruits

32)

Auxin causes the bending of plant stem towards light as well as

the curling of plant tendrils around a support.

33)

Animal hormones do not bring about directional growth

depending on environmental cues, but promote controlled growth in various areas to maintain the body design.

34)

The various endocrine glands in humans are hypothalamus,

pineal gland, pituitary gland, thyroid gland, parathyroid glands, thymus, pancreas, adrenal glands, ovary (in female) and testis (in males).

35)

Some important hormones and their functions in human body:

Hormone

Endocrine

Function

gland Growth

Pituitary

Regulates growth and development of body

Thyroid

Controls carbohydrate, protein and fat

gland

metabolism

Adrenal

Prepares the body to deal with emergency

gland

situations

Insulin

Pancreas

Regulates blood sugar levels

Testosterone

Testis

Causes development of sexual organs and

hormone Thyroxin

Adrenaline

secondary sexual characteristics in males Oestrogen

Ovary

Causes development of sexual organs and secondary sexual characteristics in females

35) In case of flight or fight reaction to an emergency situation, Adrenal glands
release adrenaline into blood
which acts on heart and other tissues
causes faster heart beat
more oxygen to muscles
reduced blood supply to digestive system and skin
diversion of blood to skeletal muscles
increase in breathing rate. 36) Deficiency of iodine causes goiter whereas deficiency of growth hormone and insulin causes dwarfism and diabetes respectively.

37) Feedback mechanisms are present to regulate the hormone action.

38) Difference between nervous and endocrine system

Mode of

Nervous system

Endocrine system

Electrical impulses

Chemical compounds

Very quick

Slow

Only cells connected by

All cells of the body

communication Speed of communication Can reach

nervous system Continuity

Cannot continuously

Can act steadily and

transmit impulses

persistently

Top Definitions

1) Receptors – Specialized structures at the ends of the nerve fibres that collect the information to be conducted by the nerves, and are located in the sense organs.

2) Gustatory receptors – Receptors present in tongue and capable of detecting taste.

3) Olfactory receptors – Receptors present in nose and capable of detecting smell.

4) Synapse – A specialized junction between two neurons, across which nerve impulse passes.

5) Neuromuscular junction – The junction between a nerve fiber and the muscle cell it supplies.

6) Nerve impulse – An electrochemical signal that travels through a neuron in response to a stimulus.

7) Effectors – A muscle, gland, or organ capable of responding to a stimulus, especially a nerve impulse.

8) Sensory neuron – A neuron that conducts impulses from a receptor organ to the central nervous system.

9) Motor neuron – A neuron that conducts impulses from the central nervous system to muscle or gland.

10)

Relay neuron – A neuron which connects sensory neurons with

motor neurons in neural pathways.

11)

Reflex action - An automatic, rapid, involuntary and immediate

reaction to a stimulus.

12)

Reflex arc – The neural pathway that mediates a reflex action.

13)

Cranial nerves – Nerves arising from the brain

14)

Spinal nerves – Nerves arising from the spinal cord.

15)

Tropic movements – The directional movements shown by

plants in response to environmental factors.

16)

Hormone – The secretion of an endocrine gland that is

transmitted by blood to specific tissues in the body.

17)

Phototropism – The movement of a plant towards or away from

light.

18)

Hydrotropism – The movement of a plant either towards or

away from water.

19)

Geotropism – The directional movements shown by plants in

response to gravity.

20)

Chemotropism – Movement or growth of an organism or part of

an organism in response to a chemical stimulus.

21)

Endocrine gland – A ductless gland that secretes hormones

directly into the bloodstream.

22)

Feedback mechanism – A type of self-regulating mechanism in

which the level of one substance in body influences the level of another.

Top diagrams

Structure of neuron

Neuromuscular junction

Reflex arc

Human brain

Plant showing phototropism

Plant showing geotropism

Endocrine glands in human male

Endocrine glands in human female

Chapter : How do organisms reproduce?

Key learnings: 1) Reproduction is the biological process by which new individuals of the

same kind are produced. 2) Reproduction is not essential for the survival of an organism, but is vital for the survival of a species. 3) Reproduction produces identical copies of the body design. 4) DNA is the informational macromolecule of our body. It provides information for protein synthesis. 5) During cellular reproduction, DNA duplication occurs followed by creation of an additional cellular apparatus. 6) The process of DNA copying is not accurate, resulting in variations arising during reproduction, which is the basis for evolution. 7) Variations may or may not be beneficial for the individual, but help in the survival of the species during adverse conditions. 8) Depending on their body design, the modes of reproduction differ in different organisms. 9) Reproduction is broadly divided into asexual and sexual reproduction. 10) Fission, fragmentation, regeneration, budding, vegetative propagation and spore formation are various modes of asexual reproduction. 11) Fission occurs in unicellular organisms like bacteria and protozoa through simple cell division. Depending on the number of individuals formed, fission may be binary or multiple fission.

12) On maturation, certain multi-cellular organisms (with simple body makeup) break up into smaller fragments, each of which develops into new individual. This reproductive method is called fragmentation.

13) Simple reproductive methods cannot occur in higher multicellular organisms, since they have a complex and carefully organized body structure. 14) In complex multi-cellular organism, reproduction is brought about by a single, specialized cell type that is capable of proliferating and forming all other cell types of the body. 15) Regeneration is found in many completely differentiated simple organisms, like Hydra and Planaria. If such an organism is split into several parts, most of the parts will develop into complete organisms. 16) Regeneration involves specialized totipotent cells which proliferate and differentiate to form the complete body. 17) Certain organisms like Hydra produce buds on their body surface, which mature into new individuals and separate from parent body. 18) Vegetative propagation is used by many plants, especially those incapable of producing seeds. Here, new plants are produced from roots, stems or leaves of parent plant. This reproductive method is widely used by plant breeders. 19) Spore formation is an asexual mode of reproduction found in certain multicellular organisms like Rhizopus. The thick walled spores have the capacity to develop into new individuals under suitable conditions. 20) Sexual reproduction requires both male and female sexes to produce the offspring. 21)

Sexual reproduction creates large number of novel variations.

22) In comparison to the non-reproductive body cells, the germ cells contain only half the chromosome number. 23) The male gamete is smaller and motile whereas the female gamete is larger and stores food.

24) When the offspring is produced by the union of the male and female gametes, its specific chromosome number and DNA content is re-established.

25)

In angiosperms, flower is the reproductive organ of the plant.

26) Stamen, the male reproductive part of flower, is made up of anther and filament. Carpel is the female reproductive part and is composed of stigma, style and ovary. 27) The pollen grain is present in the anther whereas the egg cell is enclosed in the ovary. 28) Pollination and fertilization are two essential events in reproduction of angiosperms. 29) Pollination is the transfer of pollen grains from anther to stigma. It may be either self-pollination or cross-pollination. 30) Pollen tube carries the male gamete from stigma to the female gamete in ovary. 31) Fertilization of male and female gametes produces the zygote, which then forms the embryo. 32) Following fertilization, the ovule develops into seed whereas the ovary forms the fruit. On germination, the seed develops into a seedling. 33)

In humans, reproduction occurs sexually.

34) Puberty is the time when the juvenile body of a person starts sexual maturation. 35) Before puberty, the body resources are used mainly to grow and develop the organism to its adult size. Once this is achieved, puberty sets in. 36) Some changes occurring during puberty are common to boys and girls, whereas other changes are specific to boys and girls. 37) Changes such as appearance of pimples on face, growth of thick hair in armpits and genital areas occur in both boys and girls.

38) Increase in breast size, darkening of nipples and occurrence of menstruation are puberty associated changes in girls. In boys, facial hair growth, cracking of voices and occasional enlargement of penis occur during puberty.

39) Changes associated with puberty are slow and gradual and does not occur uniformly in everyone. 40) The changes taking place during puberty, signals the occurrence of sexual maturation in an individual to other members of the same population. 41) In humans, the male reproductive system is composed of testes, vas deferens, seminal vesicles, prostate gland, urethra and penis. 42) Testis is situated outside the abdominal cavity. It produces sperms and secretes testosterone. 43) Sperm shows a small head containing the genetic material and a long tail, which helps in motility. 44) Vas deferens and urethra are the thin tubes through which sperms are transported from testes to outside. The sperms are nourished in the seminal fluid. 45) The female reproductive system is made up of ovaries, fallopian tubes, uterus, cervix and vagina. 46) Ovaries are responsible for production of ova/egg as well as for secreting the hormones, estrogen and progesterone. 47) On reaching puberty, ovulation occurs once a month in females, wherein one immature egg present in any one of the ovaries becomes mature and is released. This egg is carried by the fallopian tube. 48) Sperms which are introduced into the vagina of females during intercourse, may encounter the egg on reaching the fallopian tube, resulting in fertilization. 49) The zygote gets implanted in the uterus and develops into the embryo. 50) The placenta provides nourishment and oxygen to the embryo and removes the waste generated by the embryo.

51) Gestation period is nine months in humans after which the child is born due to uterine contractions.

52) In case fertilization does not occur, the released egg along with the thickened lining of the uterus is shed out through the vagina in a process called menstruation. 53) Engaging in unprotected sexual intercourse can cause pregnancy as well as spreading of sexually transmitted diseases like gonorrhea, syphilis and AIDS. 54) Condoms help to control the spread of sexually transmitted diseases. 55) Unwanted pregnancies can be avoided through several contraceptive methods. 56) Mechanical barrier methods prevent sperm from reaching the egg. E.g. – condom. 57) Oral contraceptive pills alter the hormonal balance, thereby preventing the egg from being released. 58) Surgical blocking of vas deferens in male or fallopian tube in female can also prevent pregnancy. 59) Abortions remove unwanted pregnancies, but this method is being misused to carry out female foeticide. 60) Birth control methods are essential to keep the human population in check and thereby improve the standard of living for everyone.

Top definitions 1) Reproduction - The biological process by which new individuals of the same parental kind are produced. 2) Variation – The differences found among individuals of a group or species, caused either by genetic differences or by the effect of environment on genes. 3) Asexual reproduction – Reproduction in which new generations are created from a single individual. 4) Fission – A type of asexual reproduction in which the unicellular parent organism divides into two or more parts, each developing into genetically identical individuals.

5) Binary fission – Fission in which the parent cell divides to form two similar daughter cells. 6) Multiple fission – Fission in which the parent cell divides to produce more than two daughter cells. 7) Fragmentation – The reproductive method in which certain multicellular organisms, on maturation, break up into smaller fragments, each of which develops into new individual. 8) Budding – The reproductive method in which an organism produces an outgrowth on its body surface, which then matures and develops into a new individual. 9) Vegetative propagation – The reproductive method in which new plants are produced asexually from roots, stems or leaves of the parent plant. 10) Spore - A small, usually single-celled reproductive body produced by certain fungi, bacteria, algae, and nonflowering plants, which is highly resistant to desiccation and heat and is capable of growing into a new organism. 11) Sexual reproduction - Mode of reproduction in which new individuals are produced by fusion of a male and a female gamete.

12) Pollination – Transfer of pollen grains from the anther to the stigma. 13) Self-pollination – Transfer of pollen grains from the anther to the stigma of the same flower. 14) Cross-pollination – Transfer of pollen grains from the anther of one flower to the stigma of another flower. 15) Fertilization – Fusion of male and female gametes to form zygote, which eventually develops into an embryo. 16) Germination – The process in which a seed develops into a seedling under appropriate conditions. 17) Puberty - The period during adolescence when a child's body becomes sexually mature and develops into adult form. 18) Sperm – The male reproductive cell or gamete produced in the testes.

19) Ova – The female reproductive cell or gamete produced in the ovary. 20)

Ovulation – The periodic release of an ovum from the ovary.

21) Menstruation - The monthly discharge of blood and shed mucous lining of the uterus through the vagina of non-pregnant women from puberty to menopause. 22) Contraception – The prevention of conception by the use of birth control devices or pills or surgery.

Top diagrams

Binary fission in Amoeba

Multiple fission in Plasmodium

Regeneration in Planaria

Budding in Hydra

Buds on leaf of Bryophyllum

Spore formation in Rhizopus

Longitudinal section of flower

Germination of pollen on stigma

Seed germination

Male reproductive system in humans

Female reproductive system in humans

Chapter : Heredity and Evolution

Key learning: 1) Variations arise during the process of reproduction. They may be few in asexual reproduction, but many in case of sexual reproduction. 2) The minor variations arising during asexual reproduction are caused by slight inaccuracies in DNA copying. In sexual reproduction, variations are also caused by crossing over process of meiosis. 3) Beneficial variations help the species to survive better in the environment. 4) Nature selects the beneficial variations thereby leading to evolution. 5) Reproduction produces offsprings with similar body design of the parents. However the offspring are not identical, but show a great deal of variation from the parents. 6) Sexually reproducing organisms like humans have 2 (or more) versions of genes for each trait, called alleles. 7) Gregor Johann Mendel carried out several experiments on pea plants. He carried out large number of monohybrid and dihybrid crosses using many contrasting characteristics and put forward several important conclusions. 8) In case of monohybrid cross with pure variety of plants, the phenotypic ratio obtained in F2 generation is 3:1. 9) In case of dihybrid cross involving 2 pairs of contrasting characters, the phenotypic ratio obtained in F2 generation is 9:3:3:1. 10) Mendel concluded that out of any pair of contrasting characters, one is dominant and the other recessive. 11) The homozygous dominant trait is denoted by two capital letters whereas the homozygous recessive trait is denoted by two small letters.

12) The factors or genes controlling a particular trait separate from each other during gamete formation. Hence gamete is always pure as far as contrasting characters are considered. Each gamete will possess only one gene set.

13) In crossing if two or more traits are involved, their genes assort independently, irrespective of the combinations present in the parents. 14) Genes carry information for producing proteins, which in turn control the various body characteristics. 15) For a particular trait, the offspring receives one allele from the father and one allele from the mother. 16) The combination of the male and female germ cells gives a diploid zygote. Thus the normal diploid number of chromosomes in the offspring is restored. 17) Different mechanisms are used for sex determination in different species. 18)

The sex of human offspring is genetically determined.

19) Humans have 22 pairs of autosomes and one pair of sex chromosomes. 20) Females have similar sex chromosomes XX, whereas males have an imperfect pair i.e. XY. All eggs carry X chromosome. 21) The sex of the child depends on whether the egg fuses with the sperm carrying X chromosome (resulting in a girl) or with the sperm carrying Y chromosome (resulting in a boy). 22) Variations beneficial to a species have a greater chance of flourishing in the species than the harmful or neutral variations. 23) Genetic drift can alter gene frequencies in small population and provide diversity without any survival benefits. 24) Several factors like environment, mutations, reproduction etc can cause alterations in gene frequencies in a population over generations, leading to evolution. 25) Changes occurring in the DNA of germ cells are heritable whereas changes taking place in the non-reproductive tissues are not inherited.

26) Charles Darwin proposed that evolution of species occurred by natural selection, but he did not know the underlying mechanism.

27) Natural selection, genetic drift, variations and geographical isolation can lead to speciation in sexually reproducing organisms. 28) 29) 30)

Gene flow between the members of a population prevents speciation. The fundamental characteristics used to classify organisms are presence of prokaryotic or eukaryotic cells whether the organism is unicellular or multicellular ability to perform photosynthesis presence of endoskeleton or exoskeleton in heterotrophic organisms. Classification of living organisms is closely related to their evolution.

31) As we go back in time to trace common ancestors, we find that all organisms must have arisen and radiated from a single species, which in turn originated from non-living material. Thus life arose from non-living matter. 32) Study of homologous organs, e.g. hand of man and wing of bird, helps in tracing the evolutionary relationship between different species. 33) Analogous organs, e.g. wing of insect and wing of bird, do not have common origins, but arose in different species to fulfill similar functions. 34)

Fossils help in tracing evolutionary pathways.

35) The age of fossils can be determined by using the relative method or the isotope dating method. 36) Evolution is not a one-step process, but a continuous process occurring in several stages. 37) Complex organs are formed slowly over many generations, sometimes with intermediate forms playing an important role. 38) Sometimes the use of certain features gets modified with time. For example- Feathers may have provided insulation initially, but later became associated with flight. 39) Evolutionary studies have shown that birds are closely related to reptiles.

40) Humans have carried out artificial selection for various features of cabbage and produced different vegetables. Vegetable produced Selected feature Broccoli Cauliflower Kohlrabi Kale

Arrested flower development Sterile flowers Swollen parts Larger leaves

41) Molecular phylogeny can also be used to trace evolutionary relationships. Here the DNA of different species is compared. Greater the differences in DNA, more distantly related are the species. 42) Disappearance of the existing species is not a requirement for formation of new species. 43) The new species formed are better adapted to the environment, but they need not be superior to the existing species. 44) The common ancestor of humans and chimpanzees evolved in different ways to produce the present forms. 45) Evolution produces more diverse and complex body forms over time, but the newly formed species are not more progressive than the already existing ones. So it is wrong to say that evolution produces progressive higher forms from lower ones. 46) All human beings, whether fair skinned or dark skinned, belong to the same species i.e. Homo sapiens that originated in Africa. 47) The human ancestors gradually migrated from Africa to various parts of the world like Asia, Europe, Australia and America. Thus they spread to different parts of the Earth and adapted as best as they could to their environmental conditions.

Top Definitions

1)

F1 generation- The generation resulting immediately from a cross of the first set of parents (parental generation).

2)

F2 generation – Offspring resulting from a cross of the members of F1 generation.

3)

Progeny - The offspring produced as a result of reproduction of the parents.

4)

Dominant trait - A genetic trait is considered dominant if it is expressed in a person who has only one copy of that gene.

5)

Recessive trait – A genetic trait that is expressed only when two copies of the gene are present.

6)

Homozygous – Is a situation having two identical alleles of the same gene

7)

Heterozygous - Is a situation having dissimilar alleles at corresponding chromosomal loci

8)

Monohybrid cross – A type of crossing in which only one pair of contrasting characters are considered.

9)

Dihybrid cross – A type of cross that involves two sets of characteristics.

10)

Allele – Either of a pair (or series) of alternative forms of a gene that can occupy the same locus on a particular chromosome and that control the same character.

11)

Somatic cells- All cells forming the body of an organism, except the reproductive cells.

12)

Sex chromosomes – Either of a pair of chromosomes, usually designated X or Y, in the germ cells of most animals, that combine to determine the sex and sex-linked characteristics of an individual.

13)

Gene – A segment of DNA that is involved in producing a polypeptide chain and forms the basic unit of heredity.

14)

Trait –A trait is a distinct variant of a phenotypic character of an organism that may be inherited or environmentally determined.

15)

Haploid cell – Cell having only one complete set of chromosomes

16)

Diploid cell – Cell having two sets of chromosomes, one of paternal origin, the other maternal.

17)

Micro-evolution – Evolution resulting from small specific genetic changes that can lead to a new subspecies.

18)

Genetic drift - It refers to the random change in gene frequencies in a small population, presumably owing to chance rather than natural selection, thereby providing diversity without any adaptations.

19)

Speciation - The process of formation of a new species.

20)

Homologous organs – Organs of different organisms which may be dissimilar externally, but are similar in origin and in fundamental structural plan.

21)

Analogous organs – Organs of different organisms which are similar in function and external appearance, but dissimilar in origin and structural plan.

22)

Fossils – All preserved traces of living organisms.

23)

Molecular phylogeny - The use of a gene's molecular characteristics to trace the evolutionary history of organisms.

Top diagrams / charts

Creation of diversity over succeeding generations

Pure tall pea plant

x

Pure dwarf pea plant

TT

tt ........................... Parents

↓

↓

T

t ............................ Gametes

Tt

…………………………………. F1

(Hybrid tall)

Tt

x

Tt ........................................... Selfing. T

t

T TT (Pure tall)

Tt (Hybrid tall)

t Tt (Hybrid tall)

tt( Pure dwarf)

............................................................................... F2

So the ratio of plants in F2 generation is 3(tall) : 1(short) Inheritance of a trait (e.g. height) over two generations

Plant with round green seeds RRyy ↓ Ry

× ×

RrYy (Round yellow)

Plant with wrinkled yellow seeds rrYY ........................ Parents ↓ rY ....................... Gametes

……………………………….. F1

(The gametes obtained by selfing the plants of F1 are: RY, Ry, rY, ry) On selfing the F1 plants,

Male →

RY

Ry

rY

ry

Female↓

RY

RRYY (Round yellow seeds)

RRYy (Round yellow seeds)

RrYY (Round RrYy (Round yellow seeds) yellow seeds)

Ry

RRYy (Round yellow seeds)

RRyy (Round green seeds)

RrYy (Round Rryy (Round yellow seeds) green seeds)

RrYY

RrYy

(Round yellow seeds)

(Round yellow seeds)

RrYy

Rryy

(Round yellow seeds)

(Round green seeds)

rY

ry

rrYY

rrYy

(Wrinkled (Wrinkled yellow seeds) yellow seeds)

rryy (Wrinkled (Wrinkled yellow seeds) green seeds) rrYy

…………. F2 So the ratio of plants in F2 generation is 9 (Round yellow seeds) : 3 (Round green seeds) : 3(Wrinkled yellow seeds): 1 (Wrinkled green seeds) Independent inheritance of two separate traits, shape and colour of seeds

Sex determination in humans

Homologous organs

Analogous organs (Wing of bat and wing of bird)

Fossil - invertebrate (Ammonite)

Fossil – invertebrate (Trilobite)

Fossil – dinosaur skull (Rajasaurus)

Eye-spots of Planaria

Evolution of wild cabbage

Evolution – Ladder versus tree

Chapter : Light- Reflection and Refraction

Key learnings:

1. When light falls on a body, it may be absorbed, may be transmitted or light may come back to the same medium.

2. Reflection of a light means light waves are neither transmitted nor absorbed but are deflected from the surface of the medium back into the same medium.

3. Laws of Reflection:

First law of reflection: The incident ray, the normal to the surface at the point of incidence and the reflected ray, all lie in the same plane.

Second law of reflection: The angle of incidence is equal to the angle of reflection.

4. Real image is obtained when the rays of light after reflection, actually converge at a point. It can be obtained on the screen and can be seen with the eye.

5. Virtual image forms when rays of light do not actually meet, but appear to meet when produced backwards. It cannot be obtained on the screen. 6. Characteristics of the image formed by the plane mirror: i.

The image formed by a plane mirror is always virtual and erect.

ii.

Size of image = Size of object and the image is laterally inverted.

iii.

The image formed by the plane mirror is as far behind the mirror as the object is in front.

7. Lateral Inversion: The phenomenon due to which the right side of the object appears as left and the left side of the object appears as right. That is the image is inverted sideways.

8. A spherical mirror whose reflecting surface is curved outwards and polished on the inner spherical surface is convex mirror.

9. A spherical mirror whose reflecting surface is curved inwards and polished on the outer spherical surface is concave mirror.

10. Concave mirror mostly forms real images, which can be received on the screen.

11. Convex mirror forms virtual images, which cannot be received on the screen.

12. Differentiating between a plane mirror, a concave mirror and a convex mirror, without touching them: i) If the image formed is erect and is of same size as in reality then it is a plane mirror.

ii) If the image formed is still erect but smaller in size then it is a convex mirror.

iii) If the image is erect but magnified when mirror is close to the object then it is a concave mirror.

13. Solar concentrators use huge concave mirrors to focus large amounts of solar energy thereby producing high temperature conditions in a solar power plant.

14. Concave mirrors are used as shaving and make up mirrors.

15. The centre of the reflecting surface of a spherical mirror is a point called the pole of the mirror and usually represented by P.

16. The horizontal line passing through the centre of curvature and pole of the spherical mirror is known as Principal axis.

17. The centre of curvature of a spherical mirror is the centre of the hollow sphere of glass, of which the spherical mirror is a part and usually represented by C.

18. The radius of curvature of a spherical mirror is the radius of the hollow sphere of glass, of which the spherical mirror is a part and usually represented by R.

19. The diameter of the reflecting surface that is twice the radius is called its aperture.

20. Radius of curvature (R) = 2 × focal length (f)

21. Rules for ray diagram-

i. The path of the reflected light ray depends upon how the incident ray is oriented with respect to the principal axis.

ii. A ray of light parallel to the principal axis, after reflection pass through the principal focus.

iii. A ray of light passing through the principal focus of a mirror becomes parallel to the principal axis of the mirror, on reflection

iv. A ray of light incident obliquely towards the pole of mirror is reflected obliquely as per the laws of reflection v. A ray of light passing through centre of curvature of a mirror is reflected back along the same path

22. Image formation by a concave mirror for different positions of the object Position of

Position of

object

image

At infinity

At focus F

Size of image

Nature of image

Highly

Real and

diminished,

inverted

point – sized Beyond C

Between F and

Diminished

C At C

At C

Real and inverted

Same size

Real and inverted

Between C and

Beyond C

Enlarge

F At F

Real and inverted

At infinity

Highly enlarged

Real and inverted

Between P and F

Behind mirror

Enlarged

Virtual and erect

23. Nature, position and relative size of the image formed by a convex mirror: Position of object

Position of image

Size of image

Nature of image

At infinity

At focus F behind

Highly

Virtual and

the mirror

diminished, point

erect

sized Between infinity

Between P and F

and pole of the

behind the mirror

Diminished

Virtual and erect

mirror

24. The ratio of the height of the image to the height of the object is known as the magnification.

25. Magnification is positive for virtual image and negative for real image.

26. The phenomenon of change in the path of light from one medium to another is called refraction of light.

27. The angle formed between the incident ray and the normal is called angle of incidence and the angle formed between the refracted ray and the normal is called angle of refraction.

28. The cause of refraction is the change in the speed of light as it goes from one medium to another medium.

29. Larger the difference in speeds of light, the greater will be the angle of bending and vice-versa.

30. When a ray of light passes from a rarer medium to a denser medium, it bends towards the normal. Also, the angle of incidence is greater than the angle of refraction.

31. When a ray of light passes from a denser medium to a rarer medium, it bends away from the normal. Also, the angle of incidence is less than the angle of refraction 32. Laws of refraction: The first law of refraction: The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.

Second law of refraction: The ratio of the sine of angle of incidence in the first medium to the sine of angle of refraction in the second medium is a constant for a given pair of medium and for a given wavelength of light. n=

sini sinr

where n is a constant known as refractive index of the second medium with respect to the first medium. This law is also called as Snell’s Law

33. The phenomenon of change in path of light in going from one medium to another is called refraction of light.

34. The ratio of speed of light in vacuum to the speed of light in a medium is called the refractive index of the medium. It has no unit.

35. When a ray of light traveling from a rarer to a denser medium slows down and bends towards the normal.

36. When it travels from a denser medium to a rarer medium, it speeds up and bends away from the normal.

37. The shifting of emergent ray sideways from the direction of original incident ray is called lateral displacement or lateral shift

38. The extend of the lateral shift depends on

-

the angle of incidence,

-

the thickness of slab, and

-

Refractive index of the glass slab

39. Lateral displacement is produced during refraction through a glass slab and not through a glass prism.

40. The angle through which a ray of light deviates on passing through a prism is called the angle of deviation.

41. Convex lens is thicker at the middle than at the edges.

42. Concave lens is thicker at the edges than at the middle.

43. Convex lens converge the rays of light while concave lens diverges.

44. As the object moves towards the optical centre of convex lens, the image moves away from the optical centre except when the object is placed between focus and optical centre of the lens.

45. As the object moves towards the optical centre of the convex lens, the size of image increases and it’s highly enlarged when object is at focus.

46. Power of a lens is the reciprocal of its focal length. The SI unit of power of a lens is Dioptre.

Top Formulae Mirror Formula:

1 1 1 + = v u f Magnification produced by mirror:

m=

Height of the image (h') Height of the object (h)

Snell’s law of refraction:

If I is the angle of incidence and r is the angle of refraction, then, sin i = cons tan t sin r The refractive index of medium 2 with respect to medium 1 n21 =

Speed of light in medium 1 v1 = Speed of light in medium 2 v2

The refractive index of medium 1 with respect to medium 2 n12 =

Speed of light in medium 2 v2 = Speed of light in medium 1 v1

Absolute refractive index: nm =

Lens Formula:

Speed of light in air c = Speed of light in the medium v

1 1 1 − = v u f

Magnification produced by lens: m =

Height of the Im age h' = Height of the Im age h

Magnification (m) = h’/ h = v/ u The power p of a lens of focal length f: P =

1 f

Chapter : The Human Eye and the Colorful World

Key Learnings: 1. Human eye is a valuable sense organ. Its various parts and the respective functions include:

Eye part

Eye function

Cornea

Protective layer of eye

Eye lens

Refracts the light so as to form the image on retina

Retina

Behaves as the screen on which the image is formed

Pupil

Controls the intensity of light entering the eye

Ciliary’s muscles

Adjust the thickness of the lens

2. The farthest point up to which the eye can see clearly is called the far point of the eye.

3. The distance of the closest point from the eye that can be seen clearly without accommodation is known as least distance of distinct vision.

4. The ability of the eye to observe distinctly the objects situated at widely different distances from the eye is called power of accommodation.

5. The smallest distance, at which the eye can see objects clearly without strain, is called the near point of the eye or the least distance of distinct vision. For a young adult with normal vision, it is about 25 cm.

6. In myopia distant objects are not clearly visible. It is corrected by using concave lens.

7. In hypermetropia nearby objects are not clearly visible. It is corrected by using convex lens.

8. Presbyopia arises due to weakening of ciliary muscles in old age. It can be corrected by using bi-focal lenses.

9. The phenomenon of splitting of white light into its constituent seven colors on passing through a glass prism is called dispersion of light.

10. Different colors undergo different deviations on passing through prism.

11. If a second identical prism is placed in an inverted position with respect to the first prism, all the seven colors recombine to form white light.

12. Atmospheric refraction is the phenomenon of bending of light on passing through earth’s atmosphere.

13. As we move above the surface of earth, density of air goes on decreasing.

14. Light traveling from rarer to denser layers always bends towards the normal.

15. Stars twinkle on account of atmospheric refraction.

16. Sun appears to rise 2 minutes earlier and set 2 minutes later due to atmospheric refraction.

17. The phenomenon in which a part of the light incident on a particle is redirected in different directions is called scattering of light.

18. Very small particles scatter lights of shorter wavelengths better than longer wavelengths.

19. The scattering of longer wavelengths of light increases as the size of the particles increases.

20. Larger particles scatter lights of all wavelengths equally well.

Chapter: Electricity

Key Learnings: 1. Electric current is the rate of flow of charge. 2. Battery provides the driving force required to move the charges along the wire from one terminal to another. 3. The constant voltage difference between the two terminals of the wire maintains the constant electric current through the wire. 4. Electric current is measured in terms of amperes where 1 ampere = 1 coulomb / second 5. Voltage is measured in terms of volt where 1 volt = 1 joule /coulomb

6. Resistance is a property that resists the flow of electrons in a conductor. It controls the magnitude of the current. The SI unit of resistance is ohm (Ω).

7. Resistivity is defined as the resistance offered by a cube of the material of side 1 m when the current flows perpendicular to the opposite faces of the cube. 8. Ohm’s law: The potential difference across the ends of a resistor is directly proportional to the current through it, provided its temperature remains the same. 9. The resistance of a conductor depends directly on its length, inversely on its area of cross – section, and also on the material of the conductor. 10. In Series combination of resistors: - The current flowing through each resistor is the same - The potential difference across the ends of the series combination is distributed across the resistors - The equivalent resistance is greater than the greatest resistance in the combination.

11. In Parallel combination of resistors: - The potential difference across each resistor is same and is equal to the potential difference across the combination. - The main current divides itself and a different current flow through each resistor. - The equivalent resistance is lesser than the least of all the resistances. 12. The effect of heating current due to which heat is produced in a wire when current is passed through it is called heating effect of current.

13. Electric power is the rate at which electrical energy is produced or consumed in an electric circuit. 14. The unit of power is watt (W). One watt of power is consumed when 1 A of current flows at a potential difference of 1 V. 15. The commercial unit of electric energy is kilowatt hour (kW h), commonly known a ‘unit’.

Top Formulae: 1. The current I through the cross – section of a conductor is I=

Q t

Where Q is net charge flowing across the cross – section of a conductor in time t. 2. Potential difference (V) between two points = work done (W)/ Charge (Q) V = W/ Q 3. Ohm’s law: V = I R

4. The equivalent resistance in series circuit is the sum of the individual resistances R = R1 + R2 + R3

5. The equivalent resistance of a parallel circuit containing resistances R1, R2, R3 is given as

1 1 1 1 = + + Req R1 R2 R3

6. The electric power P is given by P = VI Or

P = I2R = V²/ R

7. The electrical energy dissipated in a resistor is given by W = V × I × t 8. Joule’s law of heating; H = I2Rt 9. 1 kW h = 3, 600, 000 J = 3.6 x 106 J

Chapter: Magnetic Effects of Electric Current

Key Learnings: 1. A compass needle behaves as a small magnet. Its one end pointing towards north is called a north pole, and the other end pointing towards south, is called a south pole.

2. The space around a magnet in which the force of attraction and repulsion due to the magnet can be detected is called the magnetic field.

3. A field line is path along which a hypothetical free north pole would tend to move. The direction of the magnetic filed at a point is given by the direction that a north pole placed at that point would take. Field lines are shown closer together where the magnetic filed is greater.

4. The magnetic field lines around a straight conductor carrying current are concentric circles.

5. The direction of magnetic field is given by Right Hand Thumb Rule.

6. The magnetic field inside a solenoid is similar to that of a bar magnet.

7. A current-carrying conductor when placed in a magnetic field experiences a force.

8. Fleming’s left-hand rule gives the direction of magnetic force acting on a conductor.

9. An electromagnet consists of a core of soft iron wrapped around with a coil of insulated copper wire.

10. An electric motor is a device that converts electric energy into mechanical energy and it works on the principle of force experienced by a current carrying conductor in a magnetic field.

11. The phenomenon in which an electric current is induced in a circuit because of a changing magnetic field is called electromagnetic induction.

12. The magnetic field may change due to a relative motion between the coil and a magnet placed near to the coil. If the coil is placed near to a current carrying conductor, the magnetic field may change either due to a change in the current through the conductor or due to the relative motion between the coil and conductor.

13. Fleming’s right hand rule is used to find the direction of induced current.

14. Electric generators are based on the principle of electromagnetic induction and converts mechanical energy into electrical energy.

15. In our houses we receive AC electric power of 220 V with a frequency of 50 Hz.

16. One of the wires in the electricity wiring of houses is with red insulation, called live wire. The other one is of black insulation, which is a neutral wire. The third is the earth wire that has green insulation and this is connected to a metallic body deep inside earth.

17. The potential difference between live wire and neutral wire is 220 V.

18. Third wire in the wiring is used as a safety measure to ensure that any leakage of current to a metallic body does not give any server shock to a user.

19. Fuse is the most important safety device used for protecting the circuits due to short circuiting or overloading of the circuits.

Chapter : Sources of Energy Key Learning: 1.

A windmill is a simple machine that works with the energy of the wind. The windmill can be used to run a pump to draw water from the ground. It can also be used to run a flour mill to grind grain.

2.

The moving water also possesses kinetic energy. The water – wheel is a device used for obtaining energy from flowing water.

3.

The energy of naturally flowing water in high rivers is generally stored behind dams as potential energy and then further used to generate electricity. The electricity produced by using the energy of flowing water is known as hydro – electric power. The most important advantage of water energy is that like wind energy, it does not cause any pollution.

4.

Renewable sources of energy: The renewable sources of energy are those sources which are being produced continuously in nature and are inexhaustible. The important examples of renewable source of energy are: wood, falling water, geothermal power, sun, wind,, tides, gobar gas etc. The renewable source are also known as non – conventional sources of energy.

5.

The non – renewable sources are those sources which got accumulated in nature over a long time and can’t be quickly replaced when they get exhausted. The important examples of non – renewable sources of energy are: Coal, natural gas, petroleum, uranium, etc. The non – renewable sources are also known as conventional sources of energy.

6.

he energy radiated by the sun is called solar energy. It is interesting to note that the solar energy recovered on the earth in one day is about 50, 000 times more than the total energy consumed by all the nations of the world in one year.

7.

There are two limitations of solar energy: a. The solar energy that reaches the earth is in a very diffused form b. The solar energy is not uniformly available at all the time and all the places.

8.

Any device that gets heated by the sun’s energy is called a solar heating device. Such a device helps in collecting as much solar energy as possible. It is done by using a black pointed surface, a glass sheet cover and a reflector.

9.

A solar cooker is a heating device which is used to cook food by utilizing the energy radiated by the sun. A solar heater is used to heat water by utilizing the energy radiated by the sun. The solar power plants are used to produce electricity by using the solar energy. The solar cells are used to convert solar energy directly into electrical energy. The solar cells are made from semi- conductor elements like silicon and germanium.

10.

The oceans act as a storehouse of solar heat energy. Because the oceans covers almost 71% collector of solar heat energy. The energy collector of solar heat energy. The energy from the oceans is available in different forms. They are: a. Ocean Thermal Energy (OTE) b. Sea – waves energy c. Tidal energy d. Energy from salinity gradient in seas e. Energy from sea – vegetation f. Energy from the nuclear fusion of deuterium that is present in oceans

11.

There is always some significant temperature difference between the water ‘at the surface of ocean’ and ‘at deeper levels’. This temperature difference is even upto 2°C at enable the flow of heat. The energy

available as a result of difference in the temperature water at the surface of the ocean and at deeper levels is known as ocean thermal energy. It is also abbreviated as OTE. 12.

The rise of ocean water as a result of moon’s attraction is called ‘high tide and the fall of water is called ‘low tide’. The rise and fall of tidal waves takes place twice in a day. This gives rise to enormous movement of water between high tides and low a tides and is an excellent source of energy in many coastal areas of the world. The tidal energy can also be harnessed by constructing some tidal barrier or tidal dam.

13.

Fuels are substances which are used for producing heat energy. Fuels are sued for producing electricity.

14.

The waste material of plants and animals are called biomass. When plants and animal die, their biomass can be used as fuel.

15.

The remains of plant and animals buried under the earth millions of years ago are known as fossils. These fossils are excellent fuels and are called fossil fuels. The common examples of fusil fuels are coal, petroleum and natural gas.

16.

Petroleum is a mixture of several hydrocarbons with traces of salt, rock particles and water.

17.

Fuels used directly to produce heat are called primary fuels and fuels derived from primary fuels are known as secondary fuels.

18.

The nuclear reactor (commonly known as atomic reactor or atomic pile) is a specially designed furnace for carrying out the controlled fission of a radioactive material line U – 235 for producing atomic power. The heat energy produced from fission reactions is ultimately converted into electricity.

19.

Nuclear fuel is the fissionable material used in the nuclear reactor for producing energy by the process of fission. The nuclear fuel used is enriched which slows down the speed of neutrons so as to cause the

fission of uranium 235 effectively. Heavy water is an important moderator. 20.

The process in which an unstable nucleus of a heavy atom (like U – 235) splits up into two medium - sized nuclei with the liberation of an enormous amount of energy is called nuclear fission. 235 92U

+ 0n1 →

141 56Ba

+

92 56Kr

+ 3(0n1) + energy

Chapter : Our environment

Key learning:

1) Our environment is composed of various biotic and abiotic factors which interact with each other. 2) Human activities have a great impact on the functioning of the environment. 3) The wastes generated by the various human activities may be biodegradable or non- biodegradable. 4) The enzymes present in the body of decomposers are capable of breaking down the biodegradable substances, but not the non- biodegradable materials. 5) The non-biodegradable materials like plastic and synthetic pesticides persist in the environment for a long duration and may harm its biotic factors. 6) In an ecosystem, the abiotic and biotic factors interact to form a stable unit. 7) The size of an ecosystem ranges in size from as small as a pond or a backyard garden to as large as an entire rain forest. 8) An ecosystem may be natural (like lakes and forests) or artificial (like cropfields and aquarium). 9) The biotic factors may be classified as producers, consumers and decomposers depending on their mode of nutrition. 10) The food manufactured by the producers from simple inorganic substances is utilized directly or indirectly by the consumers. 11) Herbivores, carnivores, omnivores and parasites are the various types of consumers. 12) The decomposers break down the dead bodies and wastes of organisms and help in nutrient recycling.

13) Food chains are present in every ecosystem. Each food chain is composed of three to five trophic levels. Trophic level Organisms comprising the trophic level First Autotrophs / Producers Second Herbivores / Primary consumers Third Small carnivores / Secondary consumers Fourth Large carnivores / Tertiary consumers 14)

There is flow of energy between the various trophic levels.

15) Producers convert solar energy into chemical energy, which is then utilized by the consumers and decomposers. 16) About 1% of solar energy falling on leaves is utilized by plants in photosynthesis to produce food. 17) A large amount of energy loss occurs when the organisms of the higher trophic level feeds on the lower trophic level organisms. 18) There is only 10% flow of energy from one trophic level to the next higher level. Due to this energy loss, only 4 or 5 trophic levels are present in each food chain. 19) The number of individuals in a trophic level decreases as we go up the food chain. 20) Food webs, consisting of several interconnected food chains, are more common in mature. 21) Flow of energy is unidirectional and cannot be utilized by the previous trophic levels. 22) The non-biodegradable chemicals like pesticides and insecticides enter the food chains in land and aquatic ecosystems and then accumulate progressively at each trophic level. This is known as biological magnification. 23) Human activities can cause several environmental problems like ozone layer depletion and waste disposal. 24) Ozone, composed of three oxygen atoms, is a toxic chemical. It is formed by the combination of free oxygen atom with molecular oxygen. 25) The atmospheric ozone layer prevents the entry of solar ultraviolet rays and thus protects all organisms on Earth.

26) Use of chemicals like chlorofluorocarbons has greatly depleted the atmospheric ozone layer, which could endanger the environment.

27) The disposal of large amounts of garbage produced in any human settlement, especially in cities and towns is causing major environmental problems. 28) Changes in our lifestyle and attitude have created many disposable items, many of which are non-biodegradable. 29) Effective methods of waste disposal should be found in order to reduce the harmful effects on our environment.

Top definitions

1) Biodegradable substances – Substances that are broken down by biological processes. 2) Non- biodegradable substances – Substances that are not broken down by biological processes. 3) Ecosystem – A unit formed by all the interacting organisms in an area together with their physical environment. 4) Biotic factors – The living components of the environment such as plants, animals, which interact with each other as well as with the abiotic factors of the ecosystem. 5) Abiotic factors - The nonliving components of the environment such as water, temperature, soil and light that influence the composition and growth of an ecosystem. 6) Producers- Organisms like plants and blue green algae that produce complex organic compounds from simple inorganic molecules using energy from sunlight in presence of chlorophyll. 7) Consumers - Organisms that feed directly or indirectly on producers and cannot synthesize their own food from inorganic sources. 8) Decomposers – Organisms that feed on the dead remains and waste products of organisms and carry out nutrient cycling by breaking down the complex organic materials into simple inorganic ones.

9) Herbivore - An animal that feeds chiefly on plants.

10) Carnivores – Organisms that mainly feed on the flesh or meat of animals. 11) Omnivore - An animal that feeds on both animal and vegetable substances. 12) Parasite - An organism that lives off or in another organism, obtaining nourishment and protection while offering no benefit in return 13) Food chain - A succession of organisms in an ecological community that constitutes a continuation of food energy from one organism to another as each consumes a lower member and in turn is preyed upon by a higher member 14)

Trophic level – Each step or level of the food chain.

15) Food web - Complex network of many interconnected food chains and feeding relationships. 16) Biological magnification – A cumulative increase in the concentrations of a persistent substance in successively higher levels of the food chain.

Top diagrams

Food chain in forest

Food chain in grassland

Food chain in a pond

Trophic levels in a food chain

A food web

Ozone formation in atmosphere

Flow of energy in an ecosystem

Chapter : Management of natural resources

Key learnings:

1) The natural resources like water, soil, forests, wild-life, coal, petroleum etc. should be utilized in a sustainable manner in order to conserve our environment.

2) Over-exploitation of natural resources causes several environmental problems. 3) There are a number of laws at national and international level to safeguard our environment. 4) Ganga Action Plan was introduced in 1985 to improve the poor water quality of Ganga River. 5) The quality of water has to be assessed scientifically before utilizing it for various purposes. 6) We can adopt the 3 R’s – Reduce, Recycle and Reuse, to conserve our environment. 7) Using our resources judiciously will prevent wastage and conserve our resources. 8) Recycling materials of paper, plastic, glass etc prevents their fresh extraction thereby reducing the pressure on environment. 9) Reusing items over and over again is another environment friendly method.

10)

Sustainable development is the need of the hour to preserve our

environment. Here present human needs are met by keeping in mind the future generation needs. 11)

The participation of every individual is essential to bring about

sustainable development. 12)

Solar energy is converted into usable form by autotrophs and several

processes on Earth. 13)

Our natural resources should be available equally to everyone and

should be used without damaging the environment. 14)

We should try to preserve the number and range of biodiversity

present in a region. 15)

The stakeholders of forests are the local and tribal people of the area,

the Forest Department of the Government, the industrialists and the wild life and nature enthusiasts. 16)

The local and tribal people depend on the forest products for fulfilling

all their needs of shelter, food, transport, fuel, medicines and cattle grazing. 17)

The Forest Department of India destroyed the huge biodiversity of

forests by converting them into monocultures of commercially important plants. Such forests are useful for industrial purposes and not for local needs. 18)

Industrialists are not dependent on the forests of a particular area and

hence do not ensure sustainability of forests. 19)

The nature and wild life conservationists play an active role in

conserving the forest biodiversity.

20)

The local people should be actively involved in forest management

since they ensure its sustainability. 21)

‘Amrita Devi Bishnoi National Award for Wildlife Conservation’ is

awarded by Government of India in the memory of late Amrita Devi Bishnoi, who laid down her life for protection of trees. 22)

Deforestation is mainly caused by industrialism, tourism and

development projects. 23)

Economic and social development should be achieved with due

consideration for ecological conservation. 24)

There are many instances of strong protests by the local people

against misuse and over-exploitation of forest resources. 25)

In Chipko Andolan(which originated in the Reni village of Garhwal), the

villagers used to hug the forest trees and prevent their mass felling by the contactors. 26)

The local people use the forest resources without destroying the trees.

27)

Destruction of forests affects the soil quality and water sources, in

addition to reduced availability of forest resources. 28)

Combined working of the Forest Department with the local people can

ensure the protection and sustainability of forests. 29)

By actively involving the villagers in the management of the Arabari

forest range, the West Bengal Forest Department was able to revive the degraded Sal forests of the region.

30)

Water is an important resource as we need water for fulfilling all our

needs.

31)

Failure to maintain the ground water level in spite of the plentiful

monsoon rains is largely due to human activities like agriculture, pollution and deforestation. 32)

In pre-British India, water management was carried out locally and

optimally, according to the agricultural and daily needs of the local people. 33)

Mega-projects like large dams and canals were initiated by the British

and led to the neglect of the local water sources and irrigation methods. 34)

Dual purpose of irrigation and electricity generation is achieved by

large dams. 35)

Mismanagement of large dams and canal systems leads to unequal

distribution of water and benefits. 36)

Building large dams brings about social, economic and environmental

problems. 37)

The construction of several dams like Tehri dam and Tawa Dam

displaced several poor tribals and peasants without satisfactory rehabilitation or compensation. 38)

In watershed management, land and water resources are developed

scientifically to increase the biomass production with an aim to conserve the ecosystem. 39)

Updating the ancient water harvesting systems has recharged ground

water levels and is a viable option to the large scale water storage projects.

40)

Water harvesting techniques reduces mismanagement of water

resources and ensures benefits for the local people. State

Water harvesting structures Rajasthan Khadins, tanks, nadis Maharashtra Bandharas, tals Uttar Pradesh Bundhis Madhya Pradesh Bundhis Bihar Ahars, pynes Himachal Pradesh Kulhs Jammu Ponds Tamil Nadu Eris Kerals Surangams Karnataka Kattas 41)

Water harvesting structures replenishes the ground water levels.

42)

Ground water is polluted from pollution, breeding of mosquitoes and

evaporation and constitutes an important source of water. 43)

Fossil fuels like coal and petroleum have to be used very carefully due

to the following reasons: i)

They are present in extremely limited quantity.

ii)

Their combustion produces harmful gases such as oxides of nitrogen and sulphur and a green house gas i.e. carbon dioxide.

iii)

The huge reservoirs of carbon present in fossil fuels will be converted into carbon dioxide leading to increased global warming.

44)

Each person can help in conservation of natural resources by making

environment-friendly choices in life as much as possible.

45)

Sustainable management of natural resources is the only option

available to conserve our natural resources and ensure its equitable distribution to everyone.

Top definitions 1) Coliform – A group of bacteria found in human intestines, whose presence in water indicates contamination by disease-causing microorganisms.

2) Recycling - The act of processing used or abandoned materials for use in creating new products. 3) Reuse – The act of using an item more than once. 4) Sustainable development – A pattern of resource use for obtaining economic and social growth of the present generation while preserving the resources for the needs of future generations. 5) Chipko Andolan – A grassroot level movement in which the villagers used to hug the forest trees and prevent their mass felling by the contractors. 6) Fossil fuels – Fuels such as coal and petroleum formed from the decomposition of ancient animal and plant remains millions of years ago and which provide energy by combustion. 7) Water shed management – A scientific method of developing land and water resources to increase the biomass production without causing ecological imbalance. 8) Water harvesting – It refers to all the different techniques used to collect and store both runoff and rainwater so that it can be used for various purposes like irrigation, human consumption etc.

Top diagrams

An ideal setting of the khadin system