Compounds T. M. Yeung 2000

Sugar Brown sugar Main component: Sucrose, C 12 H 22 O 11 Carbohydrate: Carbon, Hydrogen & Oxygen

Cooking Oil Fats & oils are compounds contains: Carbon, Hydrogen & Oxygen Knife Soya Bean oil contains Omega 3 fatty acid. Extracted from high grade soya bean.

Acetylene C 2 H 2 Hydrocarbon Hydrogen & Carbon Fuel gas Provides a high flame temperature. It is widely used in the welding industries

Earth’s Atmosphere Composition of air: Nitrogen78% Oxygen21% Noble gases0.9% Carbon dioxide0.03% Water vapourvaries...

Earth’s Crust Abundance of Elements: Oxygen45% Silicon27% Aluminium8% Iron6%...

Substances in the Earth’s Crust Oxygen is the most/ least abundant element in the Earth’s crust… Combined forms of elements are called compounds/ mixtures. Most oxygen occurs as free element in the atmosphere. Most silicon in the Earth’s crust combine with oxygen to form...

Minerals in the Earth’s Crust Quartz –Silicon dioxide, SiO 2 Bauxite –Aluminium oxide Pyrite –Iron sulphide Calcite –Calcium carbonate

Minerals in the Earth’s Crust Quartz –Silicon dioxide Bauxite –Aluminium oxide, Al 2 O 3 Pyrite –Iron sulphide Calcite –Calcium carbonate

Minerals in the Earth’s Crust Quartz –Silicon dioxide Bauxite –Aluminium oxide Pyrite –Iron sulphide, FeS 2 Calcite –Calcium carbonate

Minerals in the Earth’s Crust Quartz –Silicon dioxide Bauxite –Aluminium oxide Pyrite –Iron sulphide Calcite –Calcium carbonate, CaCO 3

Earth’s Ocean Abundance of Elements: Hydrogen, H Oxygen, O Sodium, Na Chlorine, Cl...

Carbon Dioxide Chemical name: Carbon dioxide Chemical formula: CO 2 Elements: carbon and oxygen Covalent compound

Table Salt: Sodium chloride Common name:Salt Chemical name: Sodium chloride Chemical formula: NaCl Elements:Sodium and chlorine Ionic compound

Hydrochloric acid Chemical name: hydrochloric acid Chemical formula: HCl Elements: hydrogen and chlorine Covalent compound

Water Chemical formula: H 2 O Electrolysis of water: Water --> Hydrogen + Oxygen Burning hydrogen in oxygen: Hydrogen + Oxygen -- --> Water

Making compound from elements Burning sodium in chlorine: sodium + chlorine --> sodium chloride Burning carbon in air (oxygen): carbon + oxygen --> carbon dioxide C (s) + O 2 (g) --> CO 2 (g)

Burning carbon in air (oxygen): carbon + oxygen --> carbon dioxide C (s) + O 2 (g) --> CO 2 (g)

Composition by mass Mixture The amounts of the different substances in the mixture can vary. ethanol: water Beer10 : 90 Whisky40 : 60 Alcohol75 : 25 Compound The amount of the elements in the compound are in fixed ratio. Water, H 2 O, –H : O = 2 : 1 Carbon dioxide, CO 2 –C : O = 1: 2

Separating the constituents Mixture Constituents can be separated by simple physical method. Evaporation: Seawater --> salt and water Compound Can be separated into its elements by chemical method. Electrolysis: Water --> hydrogen + oxygen

General properties Mixture Properties are similar to the substances making up the mixture. Compound Properties are very different from the elements in it.

Melting point & boiling point Mixture Does not have sharp melting point or boiling point. Salt solution boils above 100 o C and boiling point depends on the amount of salt dissolved. Compound With sharp melting point and boiling point. Pure water boils at 100 o C under normal pressure.

Energy change during formation Mixture No or little energy change when a mixture is made. Mixing hydrogen and oxygen gives no energy. Compound Energy is usually given out or absorbed when a compound is formed. Burning hydrogen and oxygen gives out heat.

References(1) Encarta 98 Tate & Lyle Sugars (Sugar) – Lam Soon Group (Cooking oil) – Hong Hong Oxygen & Acetylene Co. Ltd. –

References(2) Oklahoma Crystal Collecting – Crystalallies (Quartz) – Volcano World (Bauxite) – bauxite.html