1 calorie is the amount of heat required to raise the temperature of:

1 g of water through 1 K

Reason — One calorie is defined as the amount of heat energy required to raise the temperature of 1 gram of water through 1 K (or 1 °C). Note that a change of 1 K is numerically equal to a change of 1 °C, so both express the same rise in temperature.