In which case more heat is required ? (i) Temperature of 1 kg of water is raised from `30^(@)C` to `100^(@)C`. (ii) Temperature of 3 kg of iorn, is raised from `30^(@)C` to `230^(@)C`. (specific heat of iron `="0.12 cal.g"^(-1).^(@)C^(-1)`.)

Explanation

Heat gained in the first case
`=mxxsxx(t_(2)-t_(1))`
`[m=1000g, t_(1)=30^(@)C, t_(2)=100^(@)C]`
`=1000xx1xx(100-30)`
`=1000xx70="70000 cal"`
Heat gained in the second case
`=mxxsxx(t_(2)-t_(1))[m=3000g, t_(1)=30^(@)C,t_(2)=230^(@)C, s=0.12cal.g^(-1).^(@)C^(-1)]`
`=3000xx0.12xx(230-30)="72000 cal"`
Therefore in the second case, more heat is required.