# Temperature - Meaning, Definition and Types

## Introduction:

Temperature refers to the hotness or coldness of a body. In specific terms, it is the way of determining the kinetic energy of particles within an object, a kind of energy that is associated with the motion. Fast is the movement of the particles; more is the temperature and vice versa.

The terms ‘Cold’ or ‘Hot’ are not scientific terms. If it is real to specify how much hot or cold something is, then we need to use the term Temperature. For example, to determine how hot a melted iron is, a Physicist will measure it in temperature rather than mentioning hot or cold.

Hence, temperature can be defined as “The measure of warmth or the coldness of a substance or object with reference to some standard value.” or in other way it can be said “The measure of ability of a substance, or any physical system, used to transfer the heat energy to another physical system.”

Temperature is almost important in all the fields of Science starting right from Physics, Chemistry, Geology, Atmospheric Sciences, Biology, Medicine and as well in most aspects of our daily life.

### Temperature Measurement:

Why is this temperature related to the kinetic energy of molecules say matter? This is because the temperature of the object is well approximated with the kinetic energy of the substances. The high temperature means that the molecules within the object are moving at a faster rate.

But the question arises, how to measure it? Molecules in any physical object are very small to analyze and calculate its movement (Kinetic energy) in order to measure its temperature.

As the heat is applied to a substance or a object, the molecules move in a rapid rate. The increased motion of the particles or molecules cause small expansion in volume in the object. There are various devices which, based on the phenomenon of movement of molecules, measures the temperature of an object.

Temperature Sensor Types:

• Thermocouples
• Resistor temperature detectors
• Thermistors
• Infrared sensors
• Semiconductors
• Thermometers

### Thermometer:

Thermometer is the most common instrument to measure temperature. There are various kinds of thermometers. Some of them are like glass tubes which look thin and are filled with some kind of liquid. Mostly Alcohol and Mercury are used in thermometers as they remain in liquid form even with a change of temperature in them. A small change in the temperature causes change in volume of a liquid. However, this form of effect is maximized when liquid expands within the thin tube of thermometer.

Thermometers measure the temperature due to the thermal expansion. Increase in the volume of substance because of increase in the temperature is known as Thermal expansion. Different types of substance expand in different quantities for a given set of temperature change. When a thermometer is introduced into an hot material, the liquid within the thermometer tends to expand and then rises. Thus, we measure this temperature by measuring expansion of an liquid in thermometer.

### Temperature Units:

Some units of temperature, degrees Fahrenheit and degrees Celsius. Kelvin is another unit of temperature that is very handy for many scientific calculations, since it begins at absolute zero, meaning it has no negative numbers. Relation between Fahrenheit, Celsius & Kelvin –

#### Fahrenheit to Celsius:

$\large ^{\circ }C= \frac{\left ( ^{\circ }F-32 \right )}{1.8}$

#### Celsius to Kelvin:

$\large K =\: ^{\circ }C + 273$

### Effects of Temperature:

An increase or decrease in temperature causes various changes in the physical and chemical processes of life. Some of those are given below-

• It affects the solubility, density, vapor pressure, physical properties of various materials along with the electrical conductivity
• The rate of a chemical reaction is also affected by the temperature.
• The thermal radiations from the surface of objects are also affected by temperature.