We explain what heat is and what the units of heat are. Their differences with temperature, types of heat and examples.
What is heat?
Heat is a form of energy that is transferred spontaneously between different areas of a body or from one body to another.
In thermodynamics, “heat” means “energy transfer.” This transfer always has a direction defined by the temperature difference between the bodies. Heat flows from the warmest body to the coldest, in order to reach an equilibrium temperature.
Heat can be transmitted in three different ways:
- Thermal radiation. Heat spreads through electromagnetic waves. All bodies emit heat in this way, unless they are at a temperature equal to absolute zero, 0 Kelvin.
- Thermal conduction. Heat is transmitted by the agitation of molecules, which causes the temperature to increase, liquids to evaporate, solids to melt and bodies to dilate.
- Thermal convection. Heat is transferred through the movement of a fluid, such as a gas and a liquid. For example, when heating water in a saucepan, the portion that is in contact with its base rises as it heats up, while the water on the surface moves down the sides as it cools and takes the place left by the hot portion.
See also: Thermal conductivity
heat units
Since heat is energy transfer, it can be measured as energy gain or loss. Therefore, it can be measured with the same unit as any other type of energy: the joule (which, in addition to heat, is used to measure work and energy).
To measure heat, two more units are used:
- Calorie Its abbreviation is lime and represents the amount of energy needed to increase 1 gram of water by 1° C.
- Kilocalorie It is abbreviated kcal and represents the energy required to raise 1 kilogram of water by 1° C.
Difference between heat and temperature
Heat and temperature are different things, although they are closely related to each other. Heat is the transfer of thermal energy from a body that has a higher temperature to one that has a lower temperature.
Temperature, on the other hand, is physical magnitude that measures the thermal state of a body and the kinetic energy of the molecules that compose it
Temperature, within the International System of Units, can be measured from three different scales: Kelvin, Celsius and Fahrenheit.
Types of heat
Different types of heat can be identified. Some of them are the following:
- Latent It is the energy necessary to modify the phase of a certain volume of a substance, that is, its state (solid, liquid or gaseous). In the change of state from solid to liquid, the latent heat is called fusion. In the change of state from liquid to gas, the latent heat is called heat of vaporization. These transitions occur without temperature changes.
- Sensitive It is the heat that generates a modification in the temperature of the body that perceives it but that does not interfere with its molecular structure or produce phase changes.
- Dry It consists of a thermal sterilization method that generates an effect similar to baking in the microorganisms that make up the body.
- Specific This is the amount of heat necessary to increase the temperature of one gram of mass of a compound by one degree.
- Molar specific This is the amount of heat necessary to increase the temperature of one mole of mass of a compound by one degree.
Examples of heat
Some everyday situations in which heat or energy transfer is present may be the following:
- When ironing clothes After plugging in the appliance, it raises its temperature, comes into contact with the fabric and helps eliminate wrinkles.
- From tea to cup When hot tea is served in a cup, the water transmits its heat to it and the cup increases its temperature (which the palms of the hand usually perceive).
- When serving food on a plate If the plate is made of ceramic or some other conductive material, the food served on it will conduct heat to it.
- Sand on the beach The temperature radiated by the sun is absorbed by the grains of sand and that heat is transported, for example, to the soles of the feet.
- From water to ice cube When an ice cube is thrown into a jar of water, the water transfers its heat to it by conduction, so the cube begins to melt.
- Chocolate melting in hand When a person holds a piece of chocolate for a while, it begins to melt due to the transfer of body heat.
- When boiling water in a kettle The heat from the flame is conducted to the base of the kettle, which is then transferred to the water and it reaches the boiling point.
- A light bulb on When the light bulb is turned on, it emits heat quickly.
References
- “Heat” in Fisicalab.
- «Definition of heat» in Electrontools.
- “The different types of heat” in Enerheating.
- «Types of heat» in Arqhys.
