Chemistry Form 5 Definition List

Chemistry Form 5 Definition List 1. Rate of reaction is the speed at which reactants are converted into products in a chemical reaction. Rate of reaction=

change in mass of reactants or products time

2. Catalyst is a substance which alters the rate of a chemical reaction but remains chemically unchanged at the end of reation. 3. Effective collision is the collision where the total amount of energy of the colliding (particles) is equal or greater than the activation energy and the colliding particles are in the correct orientation that will result in a reaction. 4. Chemical energy is the energy stored in all chemical subtances. 5. Thermochemistry is the study of changes in heat energy in chemical reactions. 6. Energy level diagram is the diagram that shows the amount of heat energy given out or absorbed which is called the rate of reaction. Symbol= ∆H

Unit=kJ

7. Endothermic reaction is a chemical reaction that absorbs heat from the surroundings. 8. Exothermic reaction is a chemical reaction that gives out heat to the surroundings. 9. Heat of reaction is the change in amount of heat in a chemical reaction. Symbol= ∆H

10. Heat change (Q) = mc

θ

m:mass of solution; c:specific heat capacity( θ

:change in temperature

-1

4.2J g ℃

-1

);

11. Heat of precipitation is the heat (change) when one mole of a precipitate is formed from their ions in aqueous solution. 12. Heat of displacement is the heat (change) when one mole of a metal is displaced from its salt solution by a more electropositive metal. 13. Heat of neutralisation is the heat (change) when one mole of water is formed from the reaction between an acid and an alkali. 14. Heat of combustion is the heat (change) when one mole of a reactant is completely burnt in oxygen under standard condition. 15. Fuel value is the amount of heat energy produced when one gram of the fuel is completely burnt in excess of -1 oxygen. ( Unit = kJ g ) 16. Soap is a sodium or potassium salt of long-chain fatty acid. 17. Saponification process is the hydrolysis of an ester by alkali. 18. Detergent is a sodium or potassium salt of alkyl sulphonic acid or alkylbenzene sulphonic acid. 19. Soft water is water that does not contain magnesium 2+ 2+ ions, Mg and calcium ions, Ca . 20. Hard water is water that contains magnesium ions, 2+ 2+ Mg and calcium ions, Ca . 21. Food addictive is a natural or synthetic substance added to food to prevent spoilage or to improve its appearance, taste or texture. 22. Preservatives is a substance added to food to slow down or prevent the growth of microorganisms. 23. Antioxidant is a substance used to slow down the deterioration of food caused by oxygen from the air. 24. Flavouring is a substance used to improve the taste of food and restore taste loss because of processing. 25. Thickener is a substance used to thicken foods.

26. Food dye is a substance used to add or restore the colour in food. 27. Stabiliser is a substance which helps to prevent an emulsion from separating out. 28. Medicine is a substance used to prevent or cure disease or to relieve pain. 29. Analgesic is a medicine used to relieve pain without causing numbness or affecting consciousness. 30. Antibiotic is a medicine used to kill or slow down the growth of bacteria. 31. Antidepressant is a medicine used to calm down a person and thus reduce tension and anxiety. 32. Antipsychotic is a medicine used to treat psychiatric illness. 33. Stimulant is a medicine which activates the level of activity arousal or alertness of the central nervous system to reduce fatigue and elevate mood in most people. 34. Organic compounds are compounds that contain the element carbon that is bonded to other elements by covalent bonds. 35. Inorganic compounds are compounds that do not contain the element carbon. 36. Hydrocarbon(C and H) contains only carbon and hydrogen. 37. Non-hydrocarbons(C,H and O,N,P,S,F,Cl,Br,I) are compounds in which some or all of the hydrogen atoms have been replaced by other atoms. 38. Saturated compound is a compound containing atoms bonded together by single covalent bond. 39. Unsaturated compound is a compound containing atoms bonded together by at least one double bond or triple bond. 40. Saturated hydrocarbons contain only single bonds. 41. Unsaturated hydrocarbons contain at least one multiple bonds.

42. Alkanes are a series of saturated hydrocarbon molecules with the general formula, Cn H2n+2 . 43. Substitution reaction is a reaction in which an atom or group of atoms replaces a hydrogen atom in the alkane molecule.(Example: Halogenation) 44. Alkenes are a series of unsaturated hydrocarbon molecules with the general formula, Cn H2n . 45. Addition reaction is a reaction that occurs in alkenes when a molecule is added across the carbon-carbon double bond.(Examples: Halogenation, hydrogenation and hydration) 46. Isomers are molecules with the same molecular formula, but with different structural formula. 47. Alcohols are a series of organic molecules with the hydroxyl functional group, -OH and general formula, Cn H2n+1 OH . 48. Carboxylic acid has the carboxyl group, -COOH attached to a hydrocarbon chain to give the general formula, Cn H2n+1 COOH . 49. Ester is a sweet smelling compound produced from a reaction between an alcohol and a carboxylic acid. (General formula: Cn H2n+1 COO Cm H2m+1 Functional group: Carboxylate group) 50. Fats are esters triglycerides formed from glycerol and fatty acids. 51. Fatty acids are long-chain carboxylic acids containing about 16 to 18 carbon atoms. 52. Natural rubber is a polymer of isoprene. 53. Vulcanized rubber is a natural rubber that has been treated with sulphur to improve its properties.