📑 Topics on this page (Jump to Topic):
📌 1. States of Matter
| State | Shape / volume | Intermolecular force |
|---|---|---|
| Solid | Fixed / fixed | Strongest |
| Liquid | Not fixed / fixed | Moderate |
| Gas | Not fixed / not fixed | Weakest |
| Plasma | Ionised gas | Sun, stars, lightning, neon signs |
| Bose–Einstein condensate | Near absolute zero | S.N. Bose and Einstein (1924–25) |
- Melting (solid→liquid), vaporisation (liquid→gas), condensation (gas→liquid), freezing (liquid→solid).
- Sublimation (solid directly to gas): camphor, naphthalene (balls), ammonium chloride, iodine, dry ice (solid CO₂). The reverse is deposition.
- Evaporation happens at the surface at any temperature; it rises with temperature, surface area and wind, and falls with humidity.
- Diffusion is fastest in gases — smell of incense/perfume spreads. LPG and CNG are liquefied/compressed by pressure.
📌 2. Elements, Compounds & Mixtures
- Element: one kind of atom (O₂, Fe). Compound: elements chemically joined in a fixed ratio (H₂O, NaCl) — properties differ from components. Mixture: any ratio, separable by physical methods.
- Homogeneous mixtures (solutions): salt water, air, alloys like brass. Heterogeneous: sand in water, oil in water.
| Type | Particle size | Examples | Tyndall effect |
|---|---|---|---|
| True solution | < 1 nm | Sugar/salt solution | No |
| Colloid | 1–1000 nm | Milk, smoke, fog, clouds, blood, jelly, butter, ink | Yes (light scatters) |
| Suspension | > 1000 nm | Muddy water, chalk in water | Yes, particles settle |
- Types of colloids: emulsion liquid-in-liquid — milk, mayonnaise; foam gas-in-liquid — shaving cream; aerosol — smoke, fog; gel — jelly, cheese.
📌 3. Methods of Separating Mixtures
| Method | Principle | Example |
|---|---|---|
| Sublimation | One component sublimes | Salt + ammonium chloride / camphor |
| Distillation | Large difference in boiling points | Pure water from sea water, acetone + water |
| Fractional distillation | Close boiling points | Petroleum refining, O₂/N₂ from air, alcohol-water |
| Centrifugation | Density and spinning | Cream from milk, blood and urine tests |
| Chromatography | Different adsorption rates | Dyes in ink/leaf pigments, drug tests in blood |
| Crystallisation | Solubility | Pure alum, sugar, copper sulphate |
| Separating funnel | Immiscible liquids | Oil + water, kerosene + water |
| Magnetic / decantation / filtration | Magnetism / density / particle size | Iron filings; mud and water |
⚠️ Exam Traps:
- Milk is a colloid (emulsion), not a true solution.
- Air is a mixture, not a compound.
- Naphthalene balls disappear by sublimation, not evaporation.
📌 4. Practice MCQs
📝 Practice MCQs (prepared by SF Prep — not PYQs)
Q1. Camphor changing directly from solid to gas is called: Practice
Correct answer: (D)
Sublimation skips the liquid state.
Sublimation skips the liquid state.
Q2. Cream is separated from milk by: Practice
Correct answer: (A)
On spinning, lighter cream stays near the centre.
On spinning, lighter cream stays near the centre.
Q3. Petroleum components are separated by: Practice
Correct answer: (B)
The components have close boiling points.
The components have close boiling points.
Q4. Which of the following is a colloid? Practice
Correct answer: (C)
Milk is an emulsion of fat in water.
Milk is an emulsion of fat in water.
Q5. The method used to separate dyes in ink is: Practice
Correct answer: (D)
Different dyes move up the paper at different rates.
Different dyes move up the paper at different rates.
Q6. Plasma state is found in: Practice
Correct answer: (A)
At very high temperature gas becomes ionised.
At very high temperature gas becomes ionised.
Q7. The Bose–Einstein condensate is linked with which Indian scientist? Practice
Correct answer: (B)
The "boson" is also named after him.
The "boson" is also named after him.
Q8. A mixture of oil and water is separated using a: Practice
Correct answer: (D)
Immiscible liquids form separate layers.
Immiscible liquids form separate layers.
Q9. Air is a: Practice
Correct answer: (A)
Its components are not chemically combined in a fixed ratio.
Its components are not chemically combined in a fixed ratio.
Q10. The Tyndall effect is shown by: Practice
Correct answer: (B)
Colloidal particles scatter light — sunbeams visible in a forest.
Colloidal particles scatter light — sunbeams visible in a forest.
Q11. Dry ice is: Practice
Correct answer: (C)
It sublimes at −78.5 °C.
It sublimes at −78.5 °C.
Q12. A mixture of salt and ammonium chloride is separated by: Practice
Correct answer: (C)
NH₄Cl sublimes on heating.
NH₄Cl sublimes on heating.
Q13. Pure water is obtained from sea water by: Practice
Correct answer: (B)
Water evaporates and condenses; salts stay behind.
Water evaporates and condenses; salts stay behind.
Q14. Which of the following is a compound? Practice
Correct answer: (A)
In H₂O, H and O are fixed in ratio; brass is an alloy (mixture).
In H₂O, H and O are fixed in ratio; brass is an alloy (mixture).
Q15. As humidity increases, the rate of evaporation: Practice
Correct answer: (C)
Moist air takes up less extra vapour.
Moist air takes up less extra vapour.
Q16. Smoke is which type of colloid? Practice
Correct answer: (D)
Solid particles are dispersed in gas.
Solid particles are dispersed in gas.
Q17. The smell of incense spreads far due to: Practice
Correct answer: (A)
Gas molecules spread out on their own; faster when hot.
Gas molecules spread out on their own; faster when hot.
Q18. Oxygen and nitrogen are obtained from air by: Practice
Correct answer: (D)
N₂ (−196 °C) boils off before O₂ (−183 °C).
N₂ (−196 °C) boils off before O₂ (−183 °C).
Q19. Muddy water is a: Practice
Correct answer: (B)
Particles are large and settle down.
Particles are large and settle down.
Q20. Shaving cream is which type of colloid? Practice
Correct answer: (C)
Gas bubbles are dispersed in a liquid.
Gas bubbles are dispersed in a liquid.