Question

If 5,100 Joules of heat are released when a sample of water freezes,what is the mass of the water?

Answer 1

15.3 grams

Explanation:

When water freezes at 0 degrees C it loses potential energy to the surroundings, without changing its temperature. This is known as the Latent Heat of Fusion of water . I.e the energy change `x` mass of water changes to `x` mass of ice under constant temperature. The same story goes for when steam at 100 degrees C condenses back to water at constant temperature, this energy change is known as the Latent Heat of Vaporization of water.

This is given by the equation:

`Q=mL` where Q is the energy released/ put in, m is the mass of the substance and L is the Latent heat of vaporization/fusion of the substance in question.

Now `Q= 5100 J`, `L= 334 J g^-1` and `m` is our uknown.

`5100=334 times m`
`m approx 15.3` grams