Question

How is the S.I unit of heat related to unit calorie ?

Answer 1

Hint:To solve this problem, we should know the concept of heat and S.I unit of heat and what is calorie.Most of us refer to the word ‘heat’ to anything that feels warm but scientifically, heat is defined as the flow of energy from a warm to a cooler object. The classification of heat is done on this basis as hot and cold. Heat energy is all around us such as in icebergs, volcanoes, and our bodies. Every matter has heat energy. The result of the movement of minute particles known as atoms, molecules, or ions in liquids, solids, and gases is nothing but heat energy. Heat energy can be transferred by one substance to another and the flow because of the temperature difference between two objects is known as heat.

Complete step by step answer:
Heat is also a form of energy so it will have the same units as that of energy. According to the International system of units (SI), Heat energy is measured in Joules(J). $1$ Joule is defined as the amount of energy exerted or work done when a force of one newton is applied over one meter distance.

$1$ calorie is defined as the amount of heat required to raise the temperature of one gram of water through one degree Celsius. Heat energy is defined as a form of energy that flows from a body at a higher temperature to a body at a comparatively low temperature. At atomic levels it is seen in the form of vibrations and it is normally called thermal energy.

The atoms vibrating with a higher speed have more thermal energy than the ones with slower vibrations. In thermodynamics we can say that thermal energy transfers from a hot body to a cold body by means of Kinetic energy. Heat energy can be calculated by using the formula:
$q = mC\Delta T$
Where $q$ gives the heat energy, $m$ is mass of the body, $C$ is specific heat constant and $\Delta T$ is the change in temperature.
As we know, energy is the ability to do work. Heat is also a form of energy. Both heat and energy can be measured using multiple units, and calories and joules are also examples of such heat units.

And as you know, the relation between Calorie and Joule is proportional to each other which means that any change in the Calorie (cal) will also lead to a change in its equivalent value in joules (J). It also implies that Joule (J) is directly proportional to Calorie (cal) which means that: When the value in terms of Calorie (cal) increases, then its value in Joule (J) increases at a rate of $4.2$ . When the value in terms of Calorie (cal) decreases, then its value in joules (J) decreases at a rate of $4.2$ .
$1$ Joule is related to unit calories in the following way: $1\, J=0.24\,calorie$ (approx).
$1\,calorie (cal) = 4.184 (approx 4.2)\,Joule$

Note: A common mistake could be that Calorie is often used as a unit for heat energy, but it is not the SI unit. One calorie is defined as the amount of energy required to raise the temperature of the body by 1 degree Celsius.