Which of the following is an element?

Which of the following are homogeneous in nature?
$(i)$ ice $(ii)$ wood $(iii)$ soil $(iv)$ air

$(a)$ List any three differences between true solution and suspension.
$(b)$ Identify colloids from the following:
Copper sulphate solution,milk,smoke,muddy water,butter,sugar solution,face cream,lemonade

Name the process associated with the following:
$(a)$ Dry ice is kept at room temperature and at one atmospheric pressure.
$(b)$ $A$ drop of ink placed on the surface of water contained in a glass spreads throughout the water.
$(c)$ $A$ potassium permanganate crystal is in a beaker and water is poured into the beaker with stirring.
$(d)$ An acetone bottle is left open and the bottle becomes empty.
$(e)$ Milk is churned to separate cream from it.
$(f)$ Settling of sand when a mixture of sand and water is left undisturbed for some time.
$(g)$ $A$ fine beam of light entering through a small hole in a dark room illuminates the particles in its path.

$(a)$ Illustrate with an example that physical and chemical changes can take place together.
$(b)$ Which of the following are chemical changes?
$(i)$ Mixing of iron filings and sand
$(ii)$ Growth of plant
$(iii)$ Rusting of iron
$(iv)$ Freezing of water

$(a)$ Calculate the mass of potassium chloride required to prepare its $40 \%$ solution in $100 \, g$ of water.
$(b)$ Explain the term solubility and the effect of temperature on it.