We explain what specific heat is and what its units are. Also, the formulas you use and some examples.
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.
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.
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
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