Find the amount of heat released if `1kg` steam at `200^(@)C` is convered into `-20^(@)C` ice.

Explanation

Heat released `DeltaQ =` heat release to convert steam at `200^(@)C` into `100^(@)C` steam `+` heat release to convert `100^(@)C` steam into `100^(@)C` water + heat release to convert `100^(@)C` water into `0^(@)C` water + heat release to convert `0^(@)C` water into `-20^(@)C`ice.
`DeltaQ = 1xx(1)/(2) xx 100 +540 xx1 xx1 xx 100 +1 xx 80 +1 xx (1)/(2) xx 20`
`= 780` kcal.