Why does on emole of carbon have a smaller mass than one mole of sulfur? how are the atomic structures of these elements different?

If you add 10ml of hot water to 10ml of cold water and the change in tempature 8°c calculate how much energy is gained by the cold water

Sodium sulfate dissolves as follows: na2so4(s) → 2na+(aq) + so42- (aq). how many moles of na2so4 are required to make 1.0 l of solution in which the na concentration is 0.10 m?

State one important difference between a physical change and a chemical change?