We explain what specific heat is and what its units are. Also, the formulas you use and some examples.
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What is specific heat?
In physics , the term specific heat , specific heat capacity or specific heat capacity to the amount of heat that a substance or a thermodynamic system is able to absorb before increasing the temperature in one unit. That is, the specific heat measures the amount of heat needed to produce that temperature variation in a unit.
The specific heat (represented by a lowercase c ) depends on other variables, such as the initial temperature , the mass of the substance or system and the heat capacity (represented by a capital C ), which is the temperature increase coefficient in a unit of the entire system or the entire mass of the substance.
In addition, the specific heat varies according to the physical state of the matter , especially in the cases of solids and gases , since its particular molecular structure affects the transmission of heat within the particle system . The same goes for atmospheric pressure conditions: the higher the pressure, the lower the specific heat.
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Specific heat units
Since in the International Measurement System the unit for heat is joules (J) , the specific heat is expressed in this system in joules per kilogram and per kelvin (J.Kg -1 .K -1 ).
Another common form of measurement involves the use of calorie per gram and per centigrade degree (cal.g -1 . ° C -1 ), and in countries or areas that use the Anglo-Saxon system, it is measured by BTUs per pound and by degree Fahrenheit. These last two, of course, outside the SI.
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Specific heat formulas
The basic formulation of the specific heat of a substance will be: c = C / m , that is, the specific heat is equal to the ratio of caloric capacity and mass. However, when this is applied to a given variation in temperature, we will talk about the average specific heat capacity (represented as ĉ ) and it will be calculated based on the following formula:
ĉ = Q / m.Δt
Where Q represents the transfer of heat energy between the system and its environment, m the mass of the system and Δt the temperature increase to which it is subjected. Thus, the specific heat ( c ) of a given temperature ( T ) will be calculated as follows:
c = lim (Δt → 0). Q / m.ΔT = 1 / m. dQ / dT
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Examples of specific heat
A simple example of specific heat is water , used to create units of measurement of this magnitude. Thus, a calorie is required to increase a gram of water at room temperature, while 0.5 calories is required to increase the temperature of the ice to -5 ° C by one degree.
Other specific heat records are:
- Aluminum: 0.215 calories per gram
- Copper: 0.0924 calories per gram
- Gold: 0.0308 calories per gram
- Iron: 0.107 calories per gram
- Silicon: 0.168 calories per gram
- Potassium: 0.019 calories per gram
- Glass: 0.2 calories per gram
- Marble: 0.21 calories per gram
- Wood: 0.41 calories per gram
- Ethyl alcohol: 0.58 calories per gram
- Mercury: 0.0033 calories per gram
- Olive oil: 0.47 calories per gram
