State how much energy is transferred in each of the following cases: 2 grams of steam at 100 degrees celsius condenses to water at 100 degrees celsius.
2 grams of boiling water at 100 degrees celsius cools to ice water at 0 degrees celsius.
2 grams of ice water at 0 degrees celsius freezes to ice at 0 degrees celsius.
2 grams of steam at 100 degrees celsius turns to ice at 0 degrees celsius.

Explanation:

When 2 gms of steam condenses to water at 100 degree latent heat of vaporization is releases which is calculated as follows

Heat released = mass x latent heat of vaporization

= 2 x 2260 = 4520 J

When 2 gms of water  at 100 degree is cooled to ice water at zero degree  heat  is releases which is calculated as follows

Heat released = mass x specific heat x( 100-0)

= 2 x 4.2 x 100 = 840 J

When 2 gms of water at zero degree  condenses to ice at zero degree latent heat of fusion  is releases which is calculated as follows

Heat released = mass x latent heat of fusion

= 2 x 334 = 668 J

When 2 grams of steam at 100 degrees Celsius turns to ice at 0 degrees Celsius heat released will be sum of all the heat released as mentioned above ie

4520 + 840 +668 = 6028 J