difference between thermal capacity and water equivalent
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Thermal capacity and water equivalent are both terms used in the field of thermodynamics to describe the ability of a substance to store or absorb heat. While they are related concepts, there are some differences between them.
1. Thermal Capacity: Thermal capacity, also known as heat capacity, refers to the amount of heat energy required to change the temperature of a substance by a certain amount. It is a property that depends on the mass and specific heat capacity of the substance. The specific heat capacity is the amount of heat energy required to raise the temperature of one unit mass of the substance by one degree Celsius (or Kelvin).
To calculate the thermal capacity of a substance, you need to know its mass and specific heat capacity. The formula for thermal capacity is:
Thermal Capacity = Mass * Specific Heat Capacity
For example, if you have a substance with a mass of 2 kg and a specific heat capacity of 500 J/kg°C, the thermal capacity would be:
Thermal Capacity = 2 kg * 500 J/kg°C = 1000 J/°C
Thermal capacity is usually expressed in units of joules per degree Celsius (J/°C) or joules per Kelvin (J/K).
2. Water Equivalent: Water equivalent is a concept that is often used in calorimetry experiments, where heat energy changes are measured by observing temperature changes in a surrounding medium, usually water. It is the mass of water that would absorb the same amount of heat energy as the substance being studied.
To determine the water equivalent, you need to know the mass of the substance and its specific heat capacity, as well as the specific heat capacity of water. The formula for water equivalent is:
Water Equivalent = Mass * Specific Heat Capacity of Substance / Specific Heat Capacity of Water
For example, if you have a substance with a mass of 1 kg, a specific heat capacity of 800 J/kg°C, and the specific heat capacity of water is 4200 J/kg°C, the water equivalent would be:
Water Equivalent = 1 kg * 800 J/kg°C / 4200 J/kg°C = 0.19 kg
The water equivalent is usually expressed in units of kilograms (kg).
In summary, thermal capacity refers to the amount of heat energy required to change the temperature of a substance, while water equivalent is the mass of water that would absorb the same amount of heat energy as the substance being studied.