Temperature (Meaning and Explanation)

We explain what temperature is, how it is measured and what scales are used. Also, types of temperatures and differences with heat.

Temperature - boiling water — Temperature is related to the notion of cold and heat.

What is temperature?

The temperature is a scalar magnitude that is defined as the amount of kinetic energy of the particles of a gaseous, liquid or solid mass. The higher the speed of the particles, the higher the temperature and vice versa.

Temperature measurement is related to the notion of cold (lower temperature) and heat (higher temperature), which can be perceived instinctively. Furthermore, the temperature acts as a reference value to determine the normal heat of the human body information that is used to estimate health states. Heat is also used for chemical, industrial and metallurgical processes.

See also: Specific heat

Temperature scales

Degrees Celsius - Temperature — On the Celsius scale, the freezing point of water is equal to 0° C.

There are different types of scales to measure temperature. The most common are:

The Celsius scale. Also known as the “Celcigrade scale”, it is the most used along with the Fahrenheit scale. On this scale, the freezing point of water is 0°C (zero degrees Celsius) and its boiling point is 100°C.
The Fahrenheit scale. It is the measure used in most English-speaking countries. On this scale, the freezing point of water occurs at 32°F (thirty-two degrees Fahrenheit) and its boiling point at 212°F.
The Kelvin scale. It is the measurement that is usually used in science and establishes “absolute zero” as the zero point, which means that the object does not give off any heat and is equivalent to -273.15 °C (degrees Celsius).
The Rankine Scale. It is the measurement commonly used in the United States for measuring thermodynamic temperature and is defined by measuring degrees Fahrenheit above absolute zero, so it lacks negative or below zero values.

How is temperature measured?

Temperature is measured using thermometric magnitudes, that is, different units that represent temperature on different scales. For this, a device called a “thermometer” is used, of which there are several types depending on the phenomenon that needs to be measured, for example:

Dilation and contraction. There are thermometers to measure gases (constant pressure gas thermometer), liquids (mercury thermometer) and solids (liquid column or bimetallic thermometer), which are elements that expand at high temperatures or contract at low temperatures.
Electrical resistance variation. Electrical resistances, that is, the flows of electrons that move through a conductive material, vary depending on the temperature they acquire. For its measurement, electrical resistance thermometers are used, such as sensors (based on a resistance capable of transforming the electrical variation into a temperature variation) and thermoelectric thermometers (which generate driving force).
Thermal radiation thermometer. Radiation phenomena emitted in the industrial sector can be measured using temperature sensors such as infrared pyrometers (to measure very low refrigeration temperatures) and optical pyrometers (to measure high temperatures of furnaces and melting metals).
Thermoelectric potential. The union of two different metals that are subjected to different temperatures generates an electromotive force that is converted into electrical potential and is measured in volts.

Temperature types

Temperature - fever — If the body temperature exceeds 37 °C, the individual suffers from fever.

There are different types of temperature and, therefore, they are measured with different tools, such as:

ambient temperature. It is the temperature that can be recorded in the spaces in which human beings operate and for its measurement an environmental thermometer is used that uses Celsius or Fahrenheit values.
body temperature. It is body temperature. 36°C is considered a normal value for humans and if the temperature exceeds 37°C (or 98°F), the individual is considered to be suffering from fever.

Other types of temperature measurement allow thermal sensation to be calculated, for example:

The dry temperature. It is the ambient temperature, without taking into account the heat radiation of the environment and humidity. It is measured with a bulb thermometer painted bright white so as not to absorb radiation.
The radiant temperature. It is the temperature of the surfaces and walls of a closed environment and is measured using a bulb thermometer.
The humid temperature. It is the temperature measured by a thermometer located in the shade, with its bulb wrapped with damp cotton and placed under a current of air. Through this system, the water in the cotton evaporates and the heat is absorbed, which generates a decrease in the temperature captured by the thermometer with respect to the ambient temperature. This results in a measure of air humidity that is used to measure wind chill.

Difference between heat and temperature

Temperature - campfire - heat — Heat is the energy resulting from the movement of molecules in matter.

Although heat and temperature are closely related concepts, they are not the same. Some differences are:

Its meaning. Heat is thermal energy that should be understood as heat transfer, which occurs when there is a temperature difference between two bodies. This transfer always has a direction and is from the body with the highest temperature to the body with the lowest temperature. Temperature, on the other hand, is a measure of the average kinetic energy of the molecules that make up matter.
Your symbol. Heat is represented by the letter Q and the temperature with the letter T.
Its effect. The transfer of heat to a body increases its temperature. Temperature is the average kinetic energy of the particles of that body, which increases if heat is delivered.
Your transmission. Heat is transmitted from one substance to another and can spread by conduction, convection or radiation. Depending on the type of heat propagation, the temperature level reached will be.
Your object for measurement. Heat is measured with a calorimeter and temperature is measured with a thermometer.
Your unit of measurement. Heat is measured in joules, calories and kilocalories. Temperature is measured in degrees Kelvin (k), Celsius (C) or Fahrenheit (F).

Examples of temperature

Some examples of temperatures are:

The temperature of a car engine that is running is 85°C.
The ambient temperature, which is considered comfortable, is between 20° and 25°C.
The temperature of the oven on to prepare a pizza is 180 °C.
The temperature of the water to boil is 100 °C.
The average body temperature is 36.5 °C.
The temperature to reach the solidification of water to the point of turning into ice is 0 °C.
The temperature, which is controlled by a “voltage regulator” located inside an electrical appliance, prevents overheating or damage to the equipment.