Mixtures & Types

• Mixture — two or more substances physically combined; variable composition.
• Homogeneous — uniform composition (salt water, air, alloys).
• Heterogeneous — non-uniform (sand + water, oil + water).
• Solution — homogeneous mixture of solute in solvent; suspension and colloid (intro).

1. Homogeneous mixture — same composition throughout; also called solution (if liquid).
2. Heterogeneous — visible phases or particles; can be separated physically.
3. Solute & solvent — in salt water: NaCl solute, water solvent.
4. Alloys — homogeneous solid mixtures (steel, brass).
5. Colloid — particle size 1–1000 nm; Tyndall effect (milk, fog).
6. Suspension — settles on standing (muddy water).
7. NCERT Ch. 2 — tincture iodine, soda water, soil, sea water.
8. Real world — air pollution (mixture); soft drinks (CO₂ dissolved).

Is milk a pure substance, solution, colloid, or suspension?

Step 1 — Milk contains water, fat, protein, lactose — variable proportions possible.
Step 2 — Not pure substance (not fixed formula).
Step 3 — Fat globules dispersed — **colloid** (shows Tyndall effect).
Step 4 — Not true solution (not ionic/molecular level uniform for all components).
Conclusion: milk is a colloidal mixture.

• Calling salt water heterogeneous (clear homogeneous solution).
• Misconception: all clear liquids are pure water.
• Confusing colloid with suspension (colloids don't settle easily).
• Thinking air is a compound (mixture of gases).
• Forgetting alloys are mixtures, not compounds.

• Define homogeneous and heterogeneous mixtures.
• Give two examples of each type.
• What is a solute and a solvent?
• What is Tyndall effect? Which mixtures show it?

Open the Practice tab for graded questions on Mixtures & Types.