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# Temperature

Temperature is a measurement of the average amount of heat or particles thermal energy that present in a substance. It gives an average measurement which is independent on the number of particles or we can say that is independent on the size of particles; for example, the temperature of small size of bowl filled with boiled water is same as the temperature of big size of bowl. It does not depend on the number of particles.

We feel temperature every day of our atmosphere. In summer, we feel hot due to high temperature while in winter, we feel cold due to less temperature. When we boil water, we increase temperature while when we freeze or cold something, we low temperature. So it is also said to measure the capacity of object to transfer its heat energy to other object. These are scientifically accurate definition. So this is also defined as the reading of thermometer. Let’s discuss about more about temperature, its conversion factors which shows how one unit of temperature is converted into its other units of value of temperature and problem based on this conversion formula.

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## Temperature Definition

Temperature of a substance is defined as the measure of the internal energy contained in the substance. Temperature is directly related to the kinetic energy of the particles, atoms and molecules of the substance. It is the average kinetic energy of the particles contained in the system.

It determines the direction of transfer of heat when two substances at different temperatures come in contact. In simple terms it can also be stated as the degree of hotness or coldness of the system.
For example: Heat always flows from the substance at the higher temperature to the substance at the lower temperature.

Thermal Equilibrium

It is a scenario in which two substances in thermal contact with each other stop to transfer or exchange energy by the process of heat. In other words, if there are two substances which are at different temperatures and are placed near to each other transfer of energy between the substance at the higher temperature and the substance at the lower temperature takes place. Transfer of energy continues until a stage is reached when the temperatures of both the substances after the energy transfer becomes same or equal. This state is termed as the state of the thermal equilibrium.

Two substances are said to be in thermal equilibrium when they are at the same temperature. After the state of thermal equilibrium is attained no transfer of energy takes place.
Zeroth Law of Thermodynamics:

If two substances x and y are separately in equilibrium (thermal equilibrium) with a third substance z, then the substances x and y are in thermal equilibrium with each other.

Heat

Heat is stated as the transfer of energy across the boundary of a system because of the difference in temperature between the system and its surroundings. When heat is transferred to the system from the surroundings, it means that the system temperature is lower than the temperature of its surroundings. When the heat is transferred from the system to the surroundings, it shows that the system is at the higher temperature. As stated heat is the transfer of energy and the transfer of energy always takes place from the region of at the higher temperature to the region at the lower temperature. Heat is the energy in flow due to temperature difference.

Atmospheric Temperature

It is defined as the temperature at different levels of the atmosphere of the earth. Atmosphere of the earth is divided into different layers and these layers are at different temperatures depending on the particles contained in them. Temperature depends on various factors, like radiations coming from the sun etc.

Example:

We have a hot cup of tea. Let’s say that the initial temperature of the tea is 80°C. If we do not drink the tea and keep it as such, after sometime its temperature would start decreasing and the tea will become cold. Here, the heat gets transferred from the tea to the surroundings which are at lower temperature than the tea until equilibrium is reached between tea and its surroundings. Heat transfer between the cup of tea and the surroundings will stop when both attain the thermal equilibrium or attain the same temperature.

Pyrometer is a non-contacting device which is used to determine the temperature of the object's surface.

## Temperature Conversion

Mainly used temperature units are Celsius(°C), Fahrenheit(°F) and Kelvin (K). Celsius(°C), Fahrenheit(°F) are relative units of the temperature, whereas Kelvin is the absolute unit of temperature.

Celsius(°C) – Earlier it was known as centigrade scale. 0°C is termed as the freezing point of the water and 100°C is the boiling point of water under 1 atmospheric pressure unit.

Temperature Conversion Formula

To convert celsius values to Fahrenheit or Kelvin values and vice versa we use the

 From Celsius(°C) To Celsius(°C) Fahrenheit [°F] = [°C] $\times$ $\frac{9}{5}$ + 32 [°C] = ([°F] - 32) x $\frac{5}{9}$ Kelvin [K] = [°C] + 273.15 [°C] = [K] - 273.
Fahrenheit ($^{\circ}$F) - In $^{\circ}$F scale, freezing point of water is 32 $^{\circ}$F and the boiling point is 212 °F, and the boiling and freezing points of water are 180 degrees apart. A single °F is $\frac {1} {180}$th part of interval between the ice point and boiling point of water. A temperature interval of one degree Fahrenheit is an interval of $\frac{5}{9}$ of a degree Celsius. Both the scales (Fahrenheit and Celsius) coincide at −40 degrees (i.e. −40 °F = −40 °C). Absolute zero in Fahrenheit is −459.67 °F.

Conversion Formulae

To convert Fahrenheit values to Celsius or Kelvin values and vice versa we use the formula –

 From Fahrenheit To Fahrenheit Celsius [oC] = ([oF]) -32) $\times$ $\frac{5}{9}$ [oF] = [oC] $\times$ $\frac{9}{5}$ + 32 Kelvin [K] = ([oF] + 459.67) $\times$ $\frac{5}{9}$ [oF] = [K] $\times$ $\frac{9}{5}$ - 459.67
Kelvin (K) - Kelvin is the absolute temperature unit. One Kelvin can be explained as the $\frac{1} {273.16}$ of the temperature of triple point of water – (i.e. 273.16 K). Kelvin is the SI temperature unit. Absolute temperature is the temperature at which the energy of the substance becomes zero.

To convert Kelvin values to Celsius or Fahrenheit values and vice versa we use the formula –

Conversion Formulae:

 From kelvin To Kelvin Celsius [oC] = [K] - 273.15 [k] = [oC] + 273.15 Fahrenheit [oF] = [K] X $\frac{9}{5}$ - 459.67 [K] = ([oF] + 459.67 ) $\times$ $\frac{5}{9}$
Use below widget to convert the temperature according to the formula.

## Temperature Conversion Problems

The following problems will help us to learn about Temperature Conversion

### Solved Examples

Question 1: Convert 50 °F to Celsius scale.
Solution:

Now here we have temperature in Fahrenheit scale. We need to convert it into the Celsius scale.

Formula to convert temperature in Fahrenheit to Celsius is
°C = $\frac {(^{\circ}F -32)}{1.8}$
= $\frac{(50 – 32)} {1.8}$
= $\frac{(18)} {1.8}$
= 10 °C

Question 2: Convert 10°C to °F.
Solution:

Now here we have temperature in Celsius scale. We need to convert it into the Fahrenheit scale.

Formula to convert temperature in Celsius to Fahrenheit is
°F = 1.8 $\times$ °C + 32
=1.8 $\times$ 10 + 32
= 18 + 32
= 50 °F

Question 3: Convert 10 °C to K.
Solution:

Now here we have temperature in Celsius scale. We need to convert it into the Kelvin scale.
K = °C + 273.15
= 10 + 273.15
= 283.15 K

Question 4: Convert 50 °F to K.
Solution:

Fahrenheit to Kelvin Formula:
K = (°F) + 459.67 ) x $\frac{5}{9}$
= (50 + 459.67) x $\frac{5}{9}$
= 283.15

Question 5: Convert 30 K to Celsius scale.
Solution:

K to Celsius scale Formula is
°C =  K - 273.15
= 30 - 273.15
= -243 °C

Question 6: Convert 30 K to Fahrenheit scale.
Solution:

Kelvin to Fahrenheit Formula = K $\times$ $\frac{9}{5}$ - 459.67
= 30 $\times$ $\frac{9}{5}$ - 459.67
= $\frac{6}{9}$ - 459.67
= 54 - 459.67
= - 405.67

 More topics in Temperature Absolute Humidity Absolute Pressure Absolute Motion Absolute Scale Absolute Zero
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