We explain what specific heat is and what its units are. Also, the formulas used to calculate it and some examples.
What is specific heat?
In physics, it is understood by specific heat (also called specific thermal capacity either specific caloric capacity) the amount of heat required for one unit of a substance to increase its temperature by one unit of degree Celsius.
The specific heat varies according to physical state of matter That is, it is different if the matter is in a solid, liquid or gaseous state because its particular molecular structure affects the transmission of heat within the system of particles. The same occurs with atmospheric pressure conditions: the higher the pressure, the lower the specific heat.
See also: Properties of matter
Specific Heat Units
Since in the International System of Measurements 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 the calorie per gram and per degree centigrade (cal.g-1.°C-1), and in countries or areas that use the Anglo-Saxon system, it is measured with BTU's per pound and per degree Fahrenheit. These last two, outside the SI.
Specific heat formulas
The most common formula to calculate the specific heat of a substance is:
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 variation to which it is subjected.
Thus, the specific heat (c) at a given temperature (T) will be calculated as follows:
c = lim (Δt→0) . Q / m.ΔT = 1/m . dQ/dT
The greater the specific heat of a substance against a certain heat supply, the less its temperature will vary. For example, we prefer to use a wooden spoon to cook and not an aluminum one since the specific heat of wood is considerably higher than that of aluminum.
Examples of specific heat
A simple example of specific heat is that of water. It takes one calorie to raise a gram of water at room temperature by one degree Celsius, that is, the specific heat of water is 1 cal.g-1.° C-1 . On the other hand, it takes 0.5 calories to increase the temperature of ice to -5°C by one degree.
Water is the common substance with the highest specific heat and therefore plays a very important role in regulating the planet's temperature.
Other specific heat records are:
- Aluminum 0.215 calories per gram per degree Celsius
- Copper 0.0924 calories per gram per degree Celsius
- Gold 0.0308 calories per gram per degree Celsius
- Iron 0.107 calories per gram per degree Celsius
- Silicon 0.168 calories per gram per degree Celsius
- Potassium 0.019 calories per gram per degree Celsius
- Glass 0.2 calories per gram per degree Celsius
- Marble 0.21 calories per gram per degree Celsius
- Wood 0.41 calories per gram per degree Celsius
- Ethyl alcohol 0.58 calories per gram per degree Celsius
- Mercury 0.0033 calories per gram per degree Celsius
- Olive oil 0.47 calories per gram per degree Celsius
