Chemistry Form 4 Definition List

Chemistry Form 4 Definition List 1. Element – a substance consists of one type of atom. 2. Compound – a substance consists two or more elements that are chemically bonded

(molecule or ions). 3. Atom – smallest particle of an element. 4. Molecule – a group of two or more atoms. 5. Ion – a positively charged / negatively charged particle. 6. Isotopes – atoms of the same element with same proton number but different nucleon

numbers. 7. Relative atomic mass of an element = the average mass of one atom of an element/

((1/12) x the mass of one carbon-12 atom) 8. Relative molecular mass of an element = the average mass of one atom of an molecule/

((1/12) x the mass of one carbon-12 atom) 9. Molecule formula – compound shows the actual number of atoms of each element that

are present in a molecule of the compound 10. Empirical formula – compound shows the simplest whole number ratio of atoms of each

element in the compound 11. Mole – amount of substance that contains as many particles as the number of atoms in

exactly 12 g of carbon-12 the symbol of mole is mol. 12. One mole – Avogadro constant – 6.02 x 1023 13. Group (Periodic Table) – vertical columns of element (similar chemical properties). 14. Periods (Periodic Table) – horizontal rows of element. 15. Valence electrons – electrons that occupy the outermost shell. 16. Ionic bond – bond formed through the transfer of electrons between atoms of metal and

non-metal to achieve the stable octet electron arrangement. 17. Ionic compound – consist of positive ions and negative ions which are held by strong

electrostatic forces of attraction. 18. Covalent bond – bond formed through the sharing of non-metal electrons to achieve the

stable duplet or octet electron arrangement.

19. Covalent compound (also simple molecular structure) – consists of neutral molecules

which are held by weak intermolecular forces (Van der Waals). 20. Alkali (base) – chemical substance which ionizes in water to produce hydroxide ions,

OH-. 21. Acid – chemical substance which ionizes in water to produce hydrogen ions, H+ or

hydroxonium ions, H3O+. 22. pH – degree of acidity or alkalinity of a solution. Scale ranges from 0 to 14. 23. pH value – measure of the concentration of hydrogen ions, H+. 24. Strong alkali – ionises (dissociates) completely in water to form hydroxide ions, OH- of

high concentration. 25. Weak alkali – ionises (dissociates) partially in water to form hydroxide ions, OH- of low

concentration. 26. Strong acid – ionises (dissociates) completely in water to form hydrogen ions, H+ of high

concentration. 27. Weak acid – ionises (dissociates) partially in water to form hydrogen ions, H+ of low

concentration. 28. Polymer – long chain molecules made up by monomer (repeating unit).

SPM Form 4 – Terminology and Concepts: Chemical Formulae and Equations – Part 1

1. Relative atomic mass, Ar is the atomic mass of an atom when compared to a standard atom 2. Standard atom: Hydrogen scale: hydrogen is the lightest atom of all and the mass of one hydrogen atom was assigned 1 unit. Weakness of Hydrogen scale: •

not too many elements can react readily with hydrogen,

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the reactive masses of some elements were not accurate,

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hydrogen exists as a gas at room temperature and

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has a number of isotopes with different masses.

Helium scale: the second lightest atom of all and the mass of one helium atom was assigned 1 unit. Weakness of Helium scale: •

Mass of 1 helium atom = 4 times the mass of a hydrogen atom

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So, mass of 1 helium atom = 4 times 1/12 mass of a carbon atom

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helium exists as a gas at room temperature and

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helium is an inert gas.

Oxygen scale: chose as the standard atom to compare the masses of atoms Weakness of Oxygen scale: •

the existence of three isotopes of oxygen were discovered,

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natural oxygen (containing all the three isotopes) as the standard (Chemist) and

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used the isotopes oxygen-16 as the standard (Physicists).

Carbon scale: standard atom of comparison internationally. •

a carbon-12 atom is 12 times heavier than an atom of hydrogen,

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used as the reference standard in mass spectrometers,

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exists as a solid at room temperature,

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most abundant carbon isotope, happening about 98.89% and

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carbon-12 is close to the agreement based on oxygen.

3. Relative molecular mass, Mr of a substances is the average mass of a molecule (two or more atoms) of the substances when compared 1/12 with of the mass of a carbon-12 atom. 4. Relative formula mass, Fr is for ionic compound which is calculated by adding up the relative atomic masses of all the atoms. 5. Example: •

Relative atomic mass, Ar of helium = 4

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Relative molecular mass, Mr of CO2 = 12 + 2(16) = 44

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Relative formula mass, Fr of NaCl = 23 + 35.5 = 58.5

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Relative formula mass, Na2CO3·10H2O = 2(23) + 12 + 3(16) + 10 [2(1) + 16] = 286

Try to solve some of the examples without looking at the answers. If you can understand this, then stay tune and log in again for Part 2 of this topic’s notes. If you cannot understand the examples, try and try and try and try and try again until you are good with it. Till then.

SPM Form 4 – Terminology and Concepts: Chemical Formulae and Equations (Part 2)

Berry Berry Scientist Italian physicist Amedeo Avogadro (Name at birth: Lorenzo Romano Amedeo Carlo Avogadro) •

Born: 9 August 1776

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Birthplace: Turin, Piedmont, Italy

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Died: 9 July 1856

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Best Known As: The guy they named Avogadro’s number after

1. Avogadro constant / Avogadro’s number is 6.02 x 1023 2. Atomic substances •

Elements – all the particles are atoms.

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Example: zinc (Zn), sodium (Na), aluminium (Al) and all noble gases, argon (Ar), helium (He) and neon (Ne).

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RAM (Relative Atomic Mass) of Na = 23

3. Molecular substances •

Covalent compounds – the particles are molecules.

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Example: carbon dioxide (CO2), water (H2O) and non-metal elements, iodine (I2), nitrogen (N2) and oxygen (O2).

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RMM (Relative Molecular Mass) of I2 = 127 + 127 = 254

4. Ionic substances •

Ionic compounds – the particles are ions.

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Example: sodium chloride (NaCl), hydrochloric acid (HCl) and potassium iodide (KI).

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RFM (Relative Formula Mass) of HCl = 1 + 35.5 = 36.5

5. Avogadro’s Law / Gas Law states that equal volumes of all gases contain the same number of molecules under the same temperature and pressure.

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Example: equal volumes of molecular hydrogen and nitrogen would contain the same number of molecules under the same temperature and pressure.

6. Volume of gas (dm3) = Number of moles of gas x Molar volume 7. Room temperature and pressure (r.t.p.) = 24 dm3 mol-1 (25°C and 1 atm) •

Example: What is the volume of 5.0 mol helium gas at s.t.p.?

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Volume of gas = Number of moles x Molar gas volume = 5.0 mol x 24 dm3 mol-1 = 120 dm3

8. Standard temperature and pressure (s.t.p.) = 22.4 dm3 mol-1 (0°C and 1 atm) •

Example: What is the volume of 5.0 mol helium gas at s.t.p.?

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Volume of gas = Number of moles x Molar gas volume = 5.0 mol x 22.4 dm3 mol-1 = 112 dm3

9. Mass (g) = Number of moles x Molar mass 10. Number of particles = Number of moles x Avogadro constant 11. Volume (dm3) = Number of moles x Molar volume Be sure to copy down all these formulae a few times on paper so that you will have a better chance recalling it in the future. Copying them onto a card to bring around will be very helpful.

SPM Form 4 – Terminology and Concepts: Chemical Formulae and Equations (Part 3) Empirical and Molecular Formulae 1. Empirical (simplest ratio of atoms of each element that present in the compound) and molecular formulae (actual number of atoms of each element that are present in one molecule of the compound) indicate: •

the types of the elements

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the symbols of the elements and the ratio of atoms or

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moles of atoms of each element in a compound.

2. Molecular formula = (empirical formula)n n is a positive number Compound Carbon dioxide Ethane Propene Glucose Quinine

Molecular formula CO2 CH3 CH2 CH2O C10H12NO

n 1 2 3 6 2

Empirical formula (CO2) = CO2 (CH3)2 = C2H6 (CH2)3 = C3H6 (CH2O)6 = C6H12O6 C20H24N2O2

3. Chemical formulae for covalent compounds. Name

Chemical

Number of each element

Nitrogen gas Oxygen gas Ammonia Water

formula N2 O2 NH3 H2O

2 nitrogen atoms 2 oxygen atoms 1 nitrogen atom and 3 hydrogen atoms 2 hydrogen atoms and 1 oxygen atom

4. Cations are positively-charged ions. Charge +1 +1 *

Cations Ammonium ion Copper(I) ion

Formula NH4+ Cu+

+1 +1 +1 * +1 +1 +1 +2 +2 +2 * +2 * +2 * +2 +2 * +2 +2 * +2 +3 +3 * +3 * +4 * +4 *

Hydrogen ion Lithium ion Nickel(I) ion Potassium ion Silver ion Sodium ion Barium ion Calcium ion Copper(II) ion Iron(II) ion Lead(II) ion Magnesium ion Manganese(II) ion Nickel(II) ion Tin(II) ion Zinc ion Aluminium ion Chromium(III) ion Iron(III) ion Lead(IV) ion Tin(IV) ion

H+ Li+ Ni+ K+ Ag+ Na+ Ba2+ Ca2+ Cu2+ Fe2+ Pb2+ Mg2+ Mn2+ Ni2+ Sn2+ Zn2+ Al3+ Cr3+ Fe3+ Pb4+ Sn4+

* refer to the Roman numerals

5. Anions are negatively-charged ions. Charge -1 -1 -1 -1 -1 -1 -1

Anions Bromide ion Chloride ion Chlorate(V) ion Ethanoate ion Fluoride ion Hydride ion Hydroxide ion

Formula BrClClO3CH3COOFHOH-

-1 -1 -1 -1 -2 -2 -2 -2 -2 -2 -2 -2 -3 -3 -3

Iodide ion Manganate(VII) ion Nitrate ion Nitrite ion Oxide ion Carbonate ion Chromate(VI) ion Dichromate(VI) ion Sulphide ion Sulphate ion Sulphite ion Thiosulphate ion Nitride ion Phosphate ion Phosphite ion

IMnO4NO3NO2O2CO32CrO42Cr2O72S2SO42SO32S2O32N3PO43PO33-

6. Chemical formulae for ionic compounds Name

Chemical formula

Zinc chloride Copper(II) sulphate Aluminium sulphate 7. Meaning of prefixes Prefix MonoDiTriTetraPenta-

Meaning 1 2 3 4 5

ZnCl2 CuSO4 Al2(SO4)3

Number of Number of cation 1 Zn2+ 2 Cu2+ 2 Al3+

anion 2 Cl2 SO423 SO42-

HexaHeptaOctaNonaDeca-

6 7 8 9 10

8. Naming of chemical (non-metal) compounds with Greek numerical prefixes. Non-metal compound Chemical formula Carbon monoxide CO Carbon dioxide CO2 Sulphur dioxide SO2 Sulphur trioxide SO3 Carbon tetrachloride CCl4 (tetrachloromethane) Form 4 – Terminology and Concepts: Chemical Formulae and Equations (Part 4) Chemical Equation 1. Importance of chemical equation: The types of reactants; the physical conditions; the quantity of reactants and products and stated in moles. nA + nB –> pC + pD 2. Reactants are written in the left side of the reaction and products are written in the right side of the reaction. •

Example 1: Word equation: Sodium hydroxide + sulphuric acid –> sodium sulphate + water Chemical equation: NaOH + H2SO4 –> Na2SO4 + H2O Balancing equation: 2NaOH + H2SO4 –> Na2SO4 + 2H2O Complete chemical equation: 2NaOH + H2SO4 –> Na2SO4 + 2H2O

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Example 2: Word equation: Aluminium + copper(II) oxide –> aluminium(III) oxide + copper

Chemical equation: Al + CuO –> Al2O3 + Cu Balancing equation: 2Al + 3CuO –> Al2O3 + 3Cu Complete chemical equation: 2Al + 3CuO –> Al2O3 + 3Cu •

Example 3: Word equation: Nitrogen + hydrogen ammonia Chemical equation: N2 + H2 NH3 Balancing equation: N2 + 3H2 2NH3 Complete chemical equation: N2 + 3H2 2NH3

3. Information obtainable from chemical equations. •

i) mass of reactants

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ii) volume of reacting gas

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iii) mass of products formed

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iv) volume of gas produced

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Example: 2 cm3 of lead (II) nitrate solution is added to excess of potassium iodide solution. How many molecules of potassium nitrate will be formed? [Relative atomic mass: N, 14; O, 16; K, 39; I, 127; Pb, 207; Avogadro's constant: 6.02 x 1023 mol-1]

Step 1: Write a complete chemical equation. •

Pb(NO3)2(aq) + 2KI(aq) –> PbI2(s) + 2KNO3(aq)

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From the equation, 1 mole of Pb(NO3)2 reacts with 2 moles of KI formed 1 mole PbI2 of and 2 moles of KNO3.

Step 2: Convert to moles. •

No. of moles of Pb(NO3)2 = Mass of Pb(NO3)2 / Relative molecular mass

= 2 / [207 + 2(14 + 3 x 16)] = 6.04 x 10-3 mol Step 3: Ratio of moles. •

Number of moles of KNO3/ Number of moles of Pb(NO3)2 = 2/1

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Number of moles of KNO3 = (2 x 6.04 x 10-3) / 1 = 12.08 x 10-3 mol

Step 4: Convert to the number of molecules of potassium nitrate. •

Number of molecules of KNO3 = 12.08 x 10-3 x 6.02 x 1023 = 7.27 x 1021

SPM Chemistry 2010 – Extra Tips and Predictions for Paper4541/3 In previous years, SPM Chemistry Paper 3 (2004-2009) has comprises of 2-3 questions with the last question typically comprise of “Planning of Experiment). Detailed information can be found from the list below: • • • • • • • •

SPM 2003 – 3 questions (No.3 – Hardness of iron and steel or Resistance to rusting of iron and steel) SPM 2004 – 3 questions (No.3 - Carbon Compound: Esters) SPM 2005 – 3 questions (No.3 – Choose one: Alloy or Rate of reaction) SPM 2006 – 2 questions (No.2 – Vulcanised and Unvulcanised rubber) SPM 2007 – 2 questions (No.2 – Electrochemical cell) SPM 2008 – 2 questions (No.2 – Group 1 – Periodic Table) SPM 2009 – 2 questions (No.2 – Salt – pH) SPM 2010 – 2 questions

The last question (planning of experiment) of Paper 3 consists of 17 marks. Based on the analysis, the questions will be ask within the Form 4 or Form 5 syllabus (Can be recommended PEKA experiments or not PEKA experiments) (It is not only Form 4 as rumoured) The question will comprise of the following part such as:

a) b) c) d) e) f) g)

Statement of the problem (2003, 2005, 2007, 2009) Aim of experiment (2004, 2006, 2008) All the variables (2003, 2005, 2006, 2007, 2008, 2009) Statement of the hypothesis (2004, 2006, 2007, 2008, 2009) List of substances and apparatus (2003, 2004, 2005, 2006, 2007, 2008, 2009) Procedure of the experiment (2003, 2004, 2005, 2006, 2007, 2008, 2009) Tabulation of data (2003, 2004, 2005, 2006, 2007, 2008, 2009)

BIT Paper 3 (SPM 2010) From above analysis, the predicted SPM 2010 last question in Paper 3 is: a) b) c) d) e) f)

Aim of experiment All the variables Statement of the hypothesis List of substances and apparatus Procedure of the experiment Tabulation of data

Each section the maximum marks will be 3 marks (3 x 6 = 18 marks). But the marks provided is 17 marks, so this would depend on the marking scheme either 1 mark will be an extra point or one of the part (a) or (f) would be 2 marks. How to answer the question? a) Statement of the problem: It always must be a question and ended with question mark. Read the question well and you will find it in the hint in the question. Start your statement of the problem with ‘How does manipulated variable affect responding variable?’ or ‘Does increasing/decreasing manipulated variable increase/decrease the responding variable?’ b) Aim of experiment: It always must be a statement and ended with full stop. Start your aim of experiment with ‘To compare … / To investigate … / To study … c) All the variables: List out all the variables and separate each variable in the following sequence. • • •

Manipulated variable: (axis-x values) Responding variable: (axis-y values) Constant variable:

d) Statement of the hypothesis: It always must be a statement and ended with full stop. ‘The manipulated variable, the higher/lower/increase/decrease responding variable’ Important note: Must follow the sequence (always start with manipulated variable and follow by responding variable).

e) List of substances and apparatus: Always separate substance and apparatus even though this is in one section. Must list everything completely to get 3 marks! Substances: (the same meaning with materials in PEKA experiments) Important note: Solution: try to give the concentration of the solution (always in the range of 0.1 – 1.0 mol dm-3) and concentrated solution (>1.0 mol dm-3) Example: • • • •

0.1 mol dm-3 of hydrochloric acid 0.5 mol dm-3 of nitric acid 1.0 mol dm-3 copper(II) suphate solution 0.5 mol dm-3 NaOH, zinc powder …

Apparatus: try to list as complete as possible (everything that can be reused in the experiment) Example: • • • • • • • • •

Stop watch measuring cylinder beaker retort stand conical flask filter funnel trough forceps tongs …

f) Procedure of the experiment: This is the hardest part to get full marks (3 marks). You need to write the procedure as complete as possible which means all steps are to be written in detail. Berry Teacher would recommend the sentence should be written in passive form sentence (same in PEKA) and it can be present or past tense (no penalty). And try to uniform it. From the previous SPM Paper 3 record, there is no penalty if you write in active form sentence but not in PEKA report! g) Tabulation of data: This is the easiest part to get one mark, as long as you draw a table (empty table / box), you will be given at least one mark. Remember to write unit in the manipulated variable column and responding variable column!