What is heat?

We explain what heat is and what are the units of heat. Their differences with temperature, types of heat and examples.

1. What is heat?

Heat is a form of energy that transfers spontaneously between different areas of a body or from one body to another.

In thermodynamics , “heat” means “energy transfer . ” This transfer occurs through friction between one body and the other and is always transferred from the hottest to the coldest, to achieve a balance.

Heat can be transmitted in three different ways:

• Thermal irradiation Heat spreads through magnetic waves and, therefore, the two bodies must not necessarily be in contact.
• Thermal conduction The heat is transmitted by the agitation of the molecules , which causes the temperature to increase, the liquids to evaporate, the solids to melt and the bodies to dilate.
• Thermal convection Heat is transferred between gases and liquids.

Within nature , matter is in three states: liquid, solid and gas. On certain occasions, when heat is applied to a substance, it can change state. This process is called “phase change” and there are the following variants:

• Regressive sublimation. Matter passes from gaseous to solid state.
• Progressive sublimation. Matter changes from solid to gaseous state.
• Evaporation or vaporization. Matter passes from liquid to gaseous state.
• Condensation. Matter passes from gaseous to liquid state.
• Solidification. Matter changes from liquid to solid state.
• Fusion. Matter passes from solid to liquid state.

2. Heat units

Since heat is energy transfer , it can be measured as gain or loss of energy. Therefore, it can be measured with the same unit as any other type of energy: the joule that, in addition to heat, serves to measure energy work .

To measure heat, two more units are used:

• Cal . 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.

3. 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 that passes from a body that has a higher temperature to a lower temperature.

Temperature, on the other hand, is a measure . It is the physical magnitude that measures the thermal state of a body and the kinetic energy of the molecules.

The temperature, within the International System of Units, can be measured from three different scales: Kelvin, Celsius and Fahrenheit.

4. Types of heat

Different types of heat can be identified. Some of them are as follows:

• Latent. It is the energy necessary to modify the phase of a given volume of a substance, going from solid substances to liquids or from liquids to gaseous substances.
• Sensitive. It is the heat that generates a change in the temperature of the substance that perceives it. While the body temperature increases, this heat does not interfere with its state or molecular structure.
• Dry. It consists of a thermal sterilization method that generates an effect similar to baking in microorganisms that make up the body.
• Of fusion. It consists of that energy that manages to change a gram of a solid substance to a liquid state without changing its temperature. This heat has the ability to break the solid bonds of matter.
• Specific . This is the amount of heat needed to increase the temperature of the mass unitof a compound by one degree. In this case, the energy comes from the modification of other energies and is the result of the vibratory movement of atoms and molecules that make up the substances.
• Molar specific. It is linked to the internal molecular constitution of the substance.

5. Heat examples

Some everyday situations in which heat or energy transfer is present can 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 and the cup increases its temperature (which the palms usually perceive).
• When serving food on a plate. If the dish is ceramic or some other conductive material, the food served in it will lead to 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 water to ice cube. When an ice cube is thrown into a jug with water, the latter transfers its heat by conduction, whereby the cube begins to melt.
• When chocolate melts in your hand. When a person holds a piece of chocolate for a while, it begins to melt following the transfer of body temperature.
• When boiling water in a turkey. The heat of the flame is conducted to the base of the turkey, which is then transferred to the water and it reaches the boiling point.
• A light bulb on. When the lamp turns on, it emits heat quickly.