We explain what heat is and what are the units of heat. Their differences with temperature, types of heat and examples.
In thermal conduction, heat is transmitted by the agitation of the molecules.
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.
Inthermodynamics, "Heat" means "energy transfer." This transfer always has a direction defined by the difference in temperature between the bodies. Heat flows from the warmer body to the colder one, in order to reach an equilibrium temperature.
Heat can be transmitted in three different ways:
- Thermal radiation. Heat spreads throughwaves electromagnetic. All bodies emit heat in this way, unless they are at a temperature equal to absolute zero, 0 Kelvin.
- Thermal conduction. The heat is transmitted by the agitation of themolecules, which causes the temperature to increase, whichliquids evaporate, that thesolid they merge and the bodies expand.
- Thermal convection. Heat is transferred through the movement of a fluid, as it can be 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 is heated, while the water from the surface runs down the sides as it cools and takes up the place left by the hot portion.
As heat is transfer ofEnergy, can be measured as gain or loss of energy. For this reason, 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 y represents the amount of energy needed to increase 1 gram ofWater at 1 ° C.
- Kilocalorie. Abbreviated kcal y represents the energy required to raise 1 kilogram of water by 1 ° C.
Difference between heat and temperature
Temperature measures the thermal state of a body and the kinetic energy of the molecules.
Heat and temperature are different things, although they are closely related to each other. Heat is the transfer of thermal energy that goes from a body that has a higher temperature to one with a lower temperature.
Temperature, on the other hand, is the physical quantity that measures the thermal state of a body and theKinetic energy of the molecules that compose it.
Types of heat
Sensible heat does not interfere with the state or the molecular structure of the body.
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, latent heat is called de fusion. In the change of state from liquid to gas, latent heat is called heat of vaporization. These transitions occur without changes in temperature.
- Sensitive. It is the heat that generates a change in the temperature of the body that perceives it but does not interfere with its molecular structure or produce phase changes.
- Dried. It consists of a method thermal sterilization that generates inmicroorganisms that give the body an effect similar to baking.
- Specific. This is the amount of heat required to increase the temperature of one gram of heat by one degree. mass of acompound.
- Specific molar. It is the amount of heat required to increase the temperature of a mole mass of a compound.
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 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).
- By serving food on a plate. If the plate is made of ceramic or some other conductive material, the food served on it will conduct the heat.
- 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 the water to the ice cube. When an ice cube is thrown into a jug of water, the water transfers its heat by conduction, so the cube begins to melt.
- When melting chocolate in hand. When a person holds a piece of chocolate for a while, it begins to melt as a result of the transfer of body heat.
- By 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 the water reaches the Boiling point.
- A lit light bulb. When the lamp is lit, it emits heat rapidly.