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?
Inphysical, is understood by specific heat (also called specific thermal capacity orspecific caloric capacity) to the amount of heat that is required for a unit of a substance to increase its temperature in a unit of degree Celsius.
Specific heat varies according toPhysical state of matter, that is, it is different if the matter is in state solid, liquid or gaseous because its particular molecular structure affects the transmission of heat within the heating system. particles. The same happens with atmospheric pressure conditions: the higherPressure, lower specific heat.
Units of specific heat
Since in the International System of measurements the unit for heat is the joules (J), the specific heat is expressed in this system in joules per kilogram and per kelvin (J.Kg-1.K-1).
Another common way of measurement It involves the use of calories 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 in BTUs per pound and per degree Fahrenheit. These last two, outside the SI.
Specific heat formulas
The most common formula for calculating the specific heat of a substance is:
ĉ = Q / m.Δt
whereQ 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 higher the specific heat of a substance versus a certain heat supply, the less its temperature will vary. For example, we prefer to use a wooden spoon for cooking and not an aluminum one since the specific heat of wood is considerably higher than that of aluminum.
It can serve you:Heat transfer
Examples of specific heat
A simple example of specific heat is that ofWater. It requires a calorie to increase one degree Celsius a gram of water at room temperature, 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 the ice by one degree to -5 ° C.
Water is the common substance with the highest specific heat and that is why it plays a very important role in regulating the temperature of the water. planet.
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