Question

Explain the following giving two examples each (a) pure substance, and (b) colloid.

Answer 1

(a) Pure substance

• Pure substances are made up of similar kinds of particles. It is of two types elements and compounds.
• Elements: They are simpler forms of substances that we can not divide further by any other simple chemical processes. Elements can exist in solid, liquid, and gaseous states.
• Examples: Oxygen, Nitrogen.
• Compounds: Different kinds of atoms combine chemically in a fixed ratio to form a compound.
• Examples: water $\left({\mathrm{H}}_2\mathrm{O}\right)$, ammonia $\left({\mathrm{NH}}_3\right)$.

(b) Colloid

• Colloids are types of mixtures where 1-1000 nm sized particles (dispersed phase) are dispersed in a dispersion medium.
• Depending upon the states of the dispersed phase and dispersion medium, different types of colloids are present like emulsion, sol, etc.
• Examples: Milk (emulsion), Smoke (aerosol).