What is the total energy needed to heat 1.0 L of water from 15°C to 98°C?
This situation is relatively simple, because there is no phase change (no melting of ice, no vaporizing of water). Therefore the quantity of heat energy needed to raise water temperature is directly proportional to a temperature change.
The general formula is `Q = c*m*Delta T,` where `Q` is the quantity of heat added (or removed), `m` is the mass of a substance, `Delta T` is the temperature change (positive or negative) and `c` is the so-called specific heat. It depends on a substance.
For water, `c approx 4.2 J/(g*C),` and one liter of water is about `1000 g.` Thus the energy needed is `4.2*1000*(98-15) approx 349 (J).` This is the answer.
That said, water has very high specific heat, almost ten times greater than that of iron, for example.