How is a calorie defined in scientific terms?

A calorie is scientifically defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius at standard atmospheric pressure. This definition is foundational in the fields of chemistry and nutrition, as it provides a unit of measurement for energy content in food and the heat energy involved in physical and chemical processes.

In this context, specifying one gram of water allows for a standardized approach to measuring thermal energy, making it applicable across various scientific disciplines. Understanding this definition is crucial for evaluating how food energy is calculated and utilized by the human body, as well as for other applications in public health.

Other definitions mentioned, such as the amount of heat to raise one pound of water or one liter of water, relate to larger quantities and are not the standard unit for measuring energy. Similarly, the definition involving a cup of water is not a precise scientific term and lacks the standardization needed for accurate measurements in scientific research.