Melting, Boiling and Evaporation Quiz

1. What happens to the temperature of a substance while it is melting?

• A. A. It rises steadily
• B. B. It falls
• C. C. It stays constant
• D. D. It rises then falls

2. What is the boiling point of water at standard atmospheric pressure?

• A. A. 0 degreesC
• B. B. 37 degreesC
• C. C. 100 degreesC
• D. D. 273 degreesC

3. Which statement correctly distinguishes evaporation from boiling?

• A. A. Evaporation happens throughout the liquid; boiling happens only at the surface
• B. B. Evaporation can occur at any temperature and only at the surface; boiling occurs throughout the liquid at a fixed temperature
• C. C. Evaporation and boiling are identical processes
• D. D. Boiling causes cooling, but evaporation does not

4. Explain why evaporation causes the temperature of the remaining liquid to fall.

• A. A. Evaporation removes mass, which automatically lowers temperature
• B. B. The particles that escape are the most energetic, leaving behind particles with lower average kinetic energy
• C. C. Evaporation always happens at the boiling point, which is a fixed low temperature
• D. D. Evaporating particles absorb energy from the air, cooling the liquid indirectly

5. A wet cloth is placed in a warm, breezy room instead of a cool, still one. Explain how each condition affects its rate of drying (evaporation), and why laying the cloth out flat rather than folded would also help.

• A. A. Warmth and breeze both slow evaporation, and folding the cloth increases surface area
• B. B. Warmth and breeze both speed up evaporation by giving particles more energy and removing escaped vapour, and laying it flat increases surface area exposed to air
• C. C. Only warmth affects evaporation rate; breeze and surface area have no effect
• D. D. Folding the cloth increases evaporation rate more than warmth or breeze do