Heat — Important Questions

Ice melts due to applied pressure, Water re-freezes when pressure is removed, Ice ball formation uses this principle

Regelation is the phenomenon where ice melts under pressure and re-freezes when pressure is removed. The melting point of ice decreases (not increases) under pressure. This principle is used in ice ball formation.

It remains constant at 0°C

During the melting of ice, temperature remains constant at 0°C (melting point) even though heat is being supplied. This heat energy is used to break the bonds between ice molecules, not to increase temperature.

Ice melting at 0°C, Water boiling at 100°C, Steam condensing to water

Latent heat is involved during phase changes at constant temperature. Ice melting at 0°C, water boiling at 100°C, and steam condensing are all phase changes. Heating water from 20°C to 30°C and cooling ice involve sensible heat, not latent heat.

Temperature at which air becomes saturated with water vapour

Dew point is the temperature at which unsaturated air becomes saturated with water vapour. Below this temperature, excess water vapour condenses into water droplets, forming dew.