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The heating value (or energy value or calorific value) of a substance, usually a fuel or food (see food energy), is the amount of heat released during the combustion of a specified amount of it. The calorific value is the total energy released as heat when a substance undergoes complete combustion with oxygen under standard conditions .
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In chemistry, heat amounts are often measured in calories. Confusingly, two units with that name, denoted "cal" or "Cal", have been commonly used to measure amounts of heat: The "small calorie" (or "gram-calorie", "cal") is exactly 4.184 J. It was originally defined so that the heat capacity of 1 gram of liquid water would be 1 cal/°C.
The calorie is a unit of energy that originated from the caloric theory of heat. [1] [2] The large calorie, food calorie, dietary calorie, kilocalorie, or kilogram calorie is defined as the amount of heat needed to raise the temperature of one liter of water by one degree Celsius (or one kelvin).
The caloric value of the producer gas is low (mainly because of its high nitrogen content), and the technology is obsolete. Improvements over producer gas, also obsolete, include water gas where the solid fuel is treated intermittently with air and steam and, far more efficiently synthesis gas where the solid fuel is replaced with methane.
The fruit of the wild strawberry is smaller than that of the garden strawberry (Fragaria × ananassa). Botanically, the fruit is classified as an aggregate accessory fruit, but it is commonly called a berry. [5] [1] Strawberries reproduce both sexually by seed, and asexually by runners .
The most widely cultivated berry of modern times, however, is the strawberry, which is produced globally at twice the amount of all other berry crops combined. [10] The strawberry was mentioned by ancient Romans, who thought it had medicinal properties, [11] but it was then not a staple of agriculture. [12]
A negative-calorie food is food that supposedly requires more food energy to be digested than the food provides. Its thermic effect or specific dynamic action —the caloric "cost" of digesting the food—would be greater than its food energy content.