Definition

1. Noun:
   • A unit of heat energy: A gram calorie is a specific, small unit of heat. It is defined as the precise amount of heat energy needed to increase the temperature of one gram of water by one degree Celsius (centigrade) at a standard atmospheric pressure of one atmosphere.

Usage

• The gram calorie is primarily used in scientific contexts, especially in chemistry, physics, and engineering, to measure small quantities of heat energy.
• It is often used to specify the energy required for or released by chemical reactions or physical processes on a small scale.
• Important Note: In nutrition and food science, the common dietary "Calorie" (capital C) is actually a kilocalorie, which is equal to 1000 gram calories.

Examples

• Noun:
  • The reaction released approximately 15 gram calories of heat.
  • One gram calorie is equivalent to approximately 4.184 joules, the SI unit of energy.

Advanced Usage

• "small calorie": This is a common synonym for gram calorie, used to distinguish it from the large dietary Calorie (kilocalorie).
  • The specific heat capacity of the substance was measured in small calories per gram per degree.

Variants and Related Words

• calorie (small c): Often used interchangeably with gram calorie, though it can sometimes cause confusion with the kilocalorie.
• kilocalorie (kcal) / Calorie (capital C): A unit equal to 1000 gram calories, used for food energy.
• joule (J): The modern SI unit of energy; 1 gram calorie ≈ 4.184 joules.

Synonyms

• small calorie
• calorie (when context is explicitly scientific and small-scale)

Notes on Meaning

• The gram calorie is a metric unit tied to the properties of water. Its definition depends on the starting temperature of the water, as the heat required varies slightly. It is typically defined for a temperature change from 14.5°C to 15.5°C.
• It is a legacy unit largely superseded by the joule in the International System of Units (SI), but it remains useful in specific fields like chemistry.

Noun

1. unit of heat defined as the quantity of heat required to raise the temperature of 1 gram of water by 1 degree centigrade at atmospheric pressure