Heat is understood from the transit of energy between bodies and can be measured in calories (cal) or joules (j). Temperature is measured in degrees Celsius (ºC), Fahrenheit (ºF) or Kelvin (K) and is related to the level of agitation of molecules.
These are two concepts from thermology, an area of Physics. In it, the concept of heat represents heat energy, the capacity of a body, of higher temperature, to transmit part of that energy to others, of lower temperature.
While the concept of temperature, properly, represents the agitation of the molecules or atoms of a substance. The hotter, the greater the movement of atoms and molecules, the colder, the less this movement.
| Heat | Temperature | |
| Characteristics | Molecular kinetic energy transit from hotter to colder bodies. | Level of agitation of molecules and atoms in relation to the thermal state. |
| How is it measured? | Calculation on the transit of thermal energy between bodies or systems. | Thermometers measure the temperature generated from the movement of molecules and atoms. |
| measurement units |
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When someone says "he's hot", it's a mistake. Nobody and nothing can possess heat. Heat is not owned or stored, what the person means refers to a thermal sensation related to the high temperature of the environment.
What is heat?
Heat means the transfer of energy from a hotter system or body to a colder one. Bodies tend to thermal equilibrium. That is, when two or more bodies have different temperatures, this temperature tends to equalize and balance.
For this, the higher temperature body gives energy to the lower one. In this way, there is a tendency for the two bodies to reach the same temperature, entering into thermal equilibrium.
Heat can travel through conduction, convection, or radiation. The first two require physical contact between the bodies, the second acts through the propagation of heat by electromagnetic waves, without the need for contact.
- Driving. When we heat the tip of an iron bar, heat is conducted and, in a short time, the whole bar will be heated.
- Convection. A pot of water on the stove creates convection zones, the hottest water rises creating movement, heating all the liquid.
- Irradiation. The Sun, even without being in contact with the Earth, radiates heat in the form of electromagnetic waves. These waves travel through space and are responsible for the temperature of the planet.
Thermal energy transfer can be measured in Joules (J) or calories (cal). Each calorie represents 4.1868 Joules of energy (1cal = 4.1868J).
These same measures are found in food and represent the amount of energy they have when we eat them.
What is temperature?
Temperature is a physics concept that determines the (kinetic) energy of molecules. This energy has an influence on the thermal state of a body (or system).
Within a system, the higher the kinetic energy of the molecules, the higher its temperature. The same goes for the opposite: the smaller the movement of molecules, the colder the system.
A thermometer is usually used to measure temperature. Thermometers contain mercury and its degree of expansion causes the level to indicate the temperature.
These values can be presented in three different scales: Celsius, Fahrenheit and Kelvin. These measurements are based on the melting point (0 °C) and boiling point (100 °C) of water. Therefore, 0 °C = 32 °F = 273K and 100 °C = 212 °F = 373K.
Formulas for converting temperature scales:
- Kelvin to Celsius: K - 273 = °C (eg: 373 K = 100°C / 373 - 273 = 100)
- Fahrenheit to Celsius: °F - 32: 1.8 = °C (e.g.: 95 °F = 35 °C / (95 - 32): 1,8 = 63: 1,8 = 35)
Heat and temperature in physics
The area of Physics that studies the relationships between thermal energy is called Thermology.
It calculates the transit of thermal energy between systems and the temperature required to change the state of each substance.
Thermology uses the concepts of heat and temperature as the basis of various thermal relationships. For example:
- specific heat
- sensible heat
- latent heat
- thermal capacity
- thermal balance
- Driving
- Convection
- Irradiation
- heat flux
- Calorie
Interested? See too:
- Greenhouse effect and global warming
- Climate and weather
