What unit measures the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius?

The correct answer is the calorie, which is defined as the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. This measurement is particularly relevant in the fields of biology and chemistry, where understanding energy transfer and temperature changes in water is critical to various processes, including metabolic reactions in living organisms.

The calorie is commonly used in nutrition to quantify the energy provided by food, highlighting its importance in biological contexts. One calorie is equivalent to approximately 4.184 joules, linking it to the joule, which is another measurement of energy, but specifically for this scenario, the calorie is the standard unit for measuring heat energy changes in water.

Other units such as BTU (British Thermal Unit) measure energy in a different context, typically for heating purposes, while watts are a measure of power, not energy. Therefore, in the context of water temperature change, the calorie is the most appropriate unit to use.