In following equiation calculate value of H: 1kg ice at `-20^@C=H+1`kg water at `100^@C`, here H means heat required to change the state of substance.

Explanation

Heat required to convert 1 kg ice at `-20^@C` into 1 kg water at `100^@C`
`=1kg` ice at `-20^@C` to 1 kg ice at `0^@C` ice at `0^@C+1kg`
water at `0^@C+1kg` water at `0^@C` to 1 kg water at `100^@C`
`=1xx(1)/(2)xx20+1xx80+1xx100=190kcal`.
So `H=-190kcal`
Negative sign indicates that 190 kcal heat is with drawn from 1 kg water at `100^@C` to convert it into 1 kg ice at `-20^@C`