❌ Wrong! Celsius is a common unit but NOT the SI unit.

✅ Correct!  +1 mark

Kelvin (K) is the SI unit of temperature. Formula: K = °C + 273. So 0°C = 273 K.

❌ Wrong! Fahrenheit is used in the USA but is not the SI unit.

❌ Wrong! Rankine is rarely used. The SI unit is Kelvin.

❌ Wrong! 100°C is the boiling point of water, not the melting point of ice.

✅ Correct!  +1 mark

Ice melts at 0°C = 273 K. This is also called the Fusion Temperature.

❌ Wrong! −10°C is below freezing — ice exists as solid at this temperature.

❌ Wrong! At 50°C water is already liquid and well above melting point.

❌ Wrong! Solids have negligible compressibility — particles are tightly packed.

❌ Wrong! Liquids have very low compressibility.

✅ Correct!  +1 mark

Gas is highly compressible — particles are far apart. That is why LPG can be compressed into a small cylinder.

❌ Wrong! Compressibility is very different in the three states.

❌ Wrong! Vaporisation is liquid → gas. Not solid → gas.

❌ Wrong! Condensation is gas → liquid.

✅ Correct!  +1 mark

Sublimation: Solid → Gas directly. Examples: camphor, naphthalene balls, dry ice (solid CO₂).

❌ Wrong! Deposition is gas → solid directly. It is the reverse of sublimation.

❌ Wrong! Boiling is a bulk phenomenon — not evaporation.

✅ Correct!  +1 mark

Only surface particles with enough kinetic energy escape. Boiling is bulk (all particles), evaporation is surface.

❌ Wrong! Evaporation is a physical change, not a chemical one.

❌ Wrong! There is no such classification as “internal phenomenon.”

❌ Wrong! You subtracted instead of adding. K = °C + 273.

✅ Correct!  +1 mark

K = °C + 273 → 25 + 273 = 298 K ✔

❌ Wrong! 273 K = 0°C. You forgot to add 25. K = 25 + 273 = 298 K.

❌ Wrong! K = 25 + 273 = 298 K, not 325 K.

❌ Wrong! Both are at 100°C but steam has extra latent heat energy.

✅ Correct!  +1 mark

Steam carries extra latent heat of vaporisation. When it condenses on skin, this hidden energy is released — causing more severe burns than boiling water.

❌ Wrong! Steam has extra latent heat energy making it more dangerous.

❌ Wrong! At the same temperature, steam always burns more severely due to latent heat, regardless of volume.

❌ Wrong! Temperature does NOT rise during melting at the melting point.

❌ Wrong! Temperature does not fall during melting either.

✅ Correct!  +1 mark

All heat supplied goes into breaking inter-particle bonds as latent heat of fusion. Temperature stays constant at 0°C until all ice melts.

❌ Wrong! Temperature at a phase change is precisely constant, never random.

❌ Wrong! Temperature DOES affect evaporation — higher temperature = faster evaporation.

❌ Wrong! Wind speed DOES affect evaporation — clothes dry faster on a windy day.

✅ Correct!  +1 mark

Colour has NO effect on evaporation. The four factors are: temperature, surface area, humidity, wind speed.

❌ Wrong! Humidity DOES affect evaporation — high humidity slows evaporation down.

❌ Wrong! Diffusion is very slow in solids — particles are tightly packed.

❌ Wrong! Diffusion in liquids is medium speed — faster than solids but slower than gases.

✅ Correct!  +1 mark

Gas particles move at high speed with large inter-particle spaces, making diffusion fastest. That is why we smell food from far away!

❌ Wrong! Diffusion rate is very different: Gas > Liquid > Solid.

✅ CORRECT!  +1 mark

Ice first absorbs latent heat of fusion (to melt), then cools further. Total heat absorbed is much more than water at 0°C, making ice a better coolant.

❌ Wrong choice. This statement is TRUE — ice absorbs much more heat than water at the same temperature.

❌ Wrong choice. This statement is FALSE. It is the OPPOSITE — Boiling is BULK, Evaporation is SURFACE.

✅ CORRECT!  +1 mark

This is FALSE. The correct fact is: Boiling = BULK phenomenon (whole liquid). Evaporation = SURFACE phenomenon (only surface particles).

✅ CORRECT!  +1 mark

Particles possess kinetic energy and are always in motion. This is why diffusion occurs spontaneously. Motion increases with temperature.

❌ Wrong choice. This is TRUE — particles are ALWAYS moving. Even in solids they vibrate.

❌ Wrong choice. This is FALSE. Solids have the STRONGEST forces. Gases have NEGLIGIBLE forces.

✅ CORRECT!  +1 mark

FALSE. Inter-particle forces: Solid (Maximum) > Liquid (Intermediate) > Gas (Negligible). Gases have the weakest, not strongest, forces.

✅ CORRECT!  +1 mark

Naphthalene sublimates — it converts directly from solid to gas without passing through liquid state. No residue is left.

❌ Wrong choice. This is TRUE — naphthalene undergoes sublimation (solid → gas).

❌ Wrong choice. This is FALSE. Ice FLOATS on water because ice is LESS dense (917 kg/m³) than liquid water (1000 kg/m³).

✅ CORRECT!  +1 mark

FALSE — Ice FLOATS. Its density (917 kg/m³) is LESS than water (1000 kg/m³) because water expands when it freezes due to its unique molecular arrangement.

✅ Answer: SOLID

Particles are tightly packed in an ordered arrangement, fixed in positions (only vibrate). Minimum inter-particle space. Maximum inter-particle force.

✅ Answer: GAS

Particles are very far apart, moving randomly at high speed. Maximum inter-particle space and kinetic energy. Negligible inter-particle forces.

✅ Answer: LIQUID

Particles are loosely and irregularly packed, can slide over each other. Fixed volume but no fixed shape. Intermediate space and force between solid and gas.