Question

How much heat is needed to heat up 70 g of water from 20oC to 80oC in kcal?

Answer 1

The amount of heat needed to heat up water

$$Q=cm\Delta t\\ ={\rm 1\: cal/g\cdot K*70\: g*(80-20)\: K}\\ =\rm4200\:cal=4.2\: \rm kcal$$