Warming things up costs energy, and every material posts its price: the specific heat capacity $c$, in joules per kilogram per degree. Water's price tag is $4200\ \mathrm{J/(kg\cdot{}^{\circ}C)}$: 4200 joules to push one kilogram up one degree. That is a famously steep price (most metals charge a tenth of it or less), and it is why a lake stays cool all afternoon while the beach sand scorches.

The bill is $Q = mc\,\Delta T$ (read aloud: Q equals m c delta-T — the kilograms, times the price per kilogram per degree, times the degrees climbed. Say it out loud once; a formula you can say is a formula you own. One friendly bookkeeping note: $c$ hands you joules, and answers usually want kilojoules — $4200\ \mathrm{J}$ is $4.2\ \mathrm{kJ}$, and keeping everything in kJ keeps the numbers small enough to trust.