Identify the dispersed phase and dispersing medium in the following colloids:
$(a)$ Fog
$(b)$ Cheese
$(c)$ Coloured gemstone

$(a)$ $7\, g$ of iron filings and $4\, g$ of sulphur powder is treated with dilute sulphuric acid at room temperature. Name the gas produced.
$(b)$ The same mixture is heated strongly,cooled and then treated with dilute sulphuric acid. Which gas would be produced?
$(c)$ What is the cause of this difference in results of chemical reaction in different conditions?

Tincture of iodine has antiseptic properties. This solution is made by dissolving

Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together. Will it be a pure substance or a mixture? Give reasons for the same.

$(a)$ Write any three points of differences between homogeneous and heterogeneous mixtures.
$(b)$ Give two reasons for supporting that water is a compound and not a mixture.

Classify the following as physical or chemical properties:
$(a)$ The composition of a sample of steel is: $98\%$ iron,$1.5\%$ carbon,and $0.5\%$ other elements.
$(b)$ Zinc dissolves in hydrochloric acid with the evolution of hydrogen gas.
$(c)$ Metallic sodium is soft enough to be cut with a knife.
$(d)$ Most metal oxides form alkalis on interacting with water.