How is a calorie defined in terms of energy?

A calorie is defined as the amount of energy required to raise the temperature of one gram of water by one degree Celsius. This definition is foundational in thermodynamics and nutrition, where calories are often used to measure energy.

In practical applications, this definition allows for a clear understanding of how much energy is involved in heating water, a common substance used in various scientific and culinary processes. This specific measurement—one gram and one degree Celsius—provides a standard way to quantify energy, making it an essential concept in both chemistry and physics.