What are the favourable qualities given to gold when it is alloyed with copper or silver for the purpose of making ornaments?

Colloidal solution appears to be homogeneous but actually it is heterogeneous. Give justification for this statement.

Fractional distillation is suitable for the separation of miscible liquids with a boiling point difference of about $25\, K$ or less. What part of the fractional distillation apparatus makes it efficient and provides an advantage over a simple distillation process? Explain using a diagram.

What is the effect of temperature on the solubility of solids in liquids?

Which of the following statements are true for pure substances?
$(i)$ Pure substances contain only one kind of particles.
$(ii)$ Pure substances may be compounds or mixtures.
$(iii)$ Pure substances have the same composition throughout.
$(iv)$ Pure substances can be exemplified by all elements other than nickel.

What volume of ethyl alcohol and water must be mixed together to prepare $250 \, mL$ of $60 \%$ by volume of alcohol in water?