(a) What is meant by (i) element (ii) Compound and (iii) mixtures? Write down the names of two elements, two compounds and two mixtures.(b) Classify the following into elements, compounds and mixtures:Marble, air, gold, Brass, Sand, Diamond, graphite, Petroleum, Common salt, Sea-water, Chalk.

(a)
(i) Element: An element is a pure substance made up of only one type of atom. It cannot be broken down into simpler substances by chemical reactions. Examples of elements include oxygen (O) and iron (Fe).

(ii) Compound: A compound is a substance composed of two or more different elements chemically bonded together in fixed proportions. Compounds can be broken down into simpler substances (elements) by chemical reactions. Examples of compounds include water (H2O) and carbon dioxide (CO2).

(iii) Mixture: A mixture is a combination of two or more substances that are physically mixed together but not chemically bonded. Mixtures can be separated into their individual components by physical means such as filtration, distillation, or evaporation. Examples of mixtures include air (a mixture of gases) and saltwater (a mixture of salt and water).

Examples:
Elements: Oxygen (O), Iron (Fe)
Compounds: Water (H2O), Carbon dioxide (CO2)
Mixtures: Air, Saltwater

(b)
Elements: Gold, Diamond, Graphite
Compounds: Common salt (sodium chloride - NaCl)
Mixtures: Marble (calcium carbonate mixed with impurities), Brass (mixture of copper and zinc), Sand, Petroleum, Sea-water, Chalk