How much energy is required to raise the temperature of 1 kg of water by 1°C?

The correct answer is based on the concept of specific heat capacity. The specific heat capacity of water is defined as the amount of energy required to raise the temperature of 1 kilogram of water by 1 degree Celsius. This quantity is approximately equal to 1 Calorie (specifically, 1 kilocalorie is often used in dietary contexts, but for the purpose of raising the temperature of water, the simple Calorie applies here).

This physical property of water indicates that it takes one Calorie of energy to increase the temperature of one kilogram of water by one degree Celsius, which is a fundamental concept in thermodynamics. The Calorie is a unit of energy that is particularly relevant in the context of heat transfer and is often used in chemistry and biology.

The other units mentioned, while related to energy, are not applicable in this specific context. A Joule is an SI unit of energy but represents a smaller amount than a Calorie when considering the energy required to heat water. A Kilojoule is simply 1,000 Joules and would be used for larger quantities of energy. Lastly, a Watt is a unit of power, not energy, and measures the rate of energy transfer or conversion.