$(a)$ Define an element.
$(b)$ Identify non-metals from the following elements: Carbon,Potassium,Silicon,Chlorine,Mercury.

$(a)$ State the difference between a pure substance and a mixture. Give one example of each.
$(b)$ Identify homogeneous mixtures from the following:
$(i)$ Smoke
$(ii)$ Brass
$(iii)$ Tincture of iodine
$(iv)$ Milk

$(a)$ What is the effect of temperature on the solubility of a solid in a liquid?
$(b)$ Why is it possible to distinguish the particles of solute from those of solvent in a suspension?

The 'sea-water' can be classified as a homogeneous as well as heterogeneous mixture. Comment.

Why is the path of light not visible in a solution when a beam of light is passed through it?

Three students $A, B$ and $C$ prepared mixtures using chalk powder,common salt and milk respectively in water. Whose mixture
$(i)$ would not leave residue on filter paper after filtration?
$(ii)$ would show Tyndall effect?
$(iii)$ would give transparent/clear solution?
$(iv)$ would settle down at the bottom when left undisturbed?
$(v)$ could be filtered by filter paper?