the specific heat of water is 4.184 j/g °c, so to heat 1 g of water by 1 °c requires 4.184 j. we note that since 4.184 j is required to heat 1 g of water by 1 °c, we will need 800 times as much to heat 8.0 × 102 g of water by 1 °c. finally, we observe that since 4.184 j are required to heat 1 g of water by 1 °c, we will need 64 times as much to heat it by 64 °c (that is, from 21 °c to 85 °c).