Example: Latent heat

On the last page you might have noticed that in the formula for Latent Heat of Fusion or Vaporization there was no mention of a change in temperature.

When a object changes phase (melts or boils) no temperature change occurs, all the energy goes into breaking the bonds.

It is important to realise that when you add ice to a glass of water, the temperature starts around 7°C. After 30 mins the temperature is still around 7°C, actually the temperature stays around 7°C until all the ice has melted which takes 60 minutes.

ice melting

It takes a 3.5 hours for the water to reach room temperature of 19.9°C.

ice melting


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