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### Theory:

Different substances behave differently to heat in different ways.

**For example**, if a metal chair is located in bright sun on a hot day, We will feel the heat while touching it. An equal mass of water in the same sun will not become nearly as hot as the chair.

The reason behind this is that the water has a high heat capacity that is the amount of heat energy necessary to increase an object's temperature by \(1\) \(°C\). Compared to metals, water is very reluctant to change with respect to temperature.

Heat Capacity:

In general, the amount of heat energy gained or lost by a substance is determined by three factors. They are,

**Mass of the substance****Change in temperature of the substance****Nature of the material of the substance**

Different substances need different amounts of heat energy to reach a particular temperature. This nature is known as the heat capacity of a substance.

Heat capacity is the amount of heat energy required by a substance to raise its temperature by \(1 °C\) or \(1 K\). It is denoted by the symbol C'.

$\mathit{Heat}\phantom{\rule{0.147em}{0ex}}\mathit{Capacity}\phantom{\rule{0.147em}{0ex}}=\frac{\mathit{Amount}\phantom{\rule{0.147em}{0ex}}\mathit{of}\phantom{\rule{0.147em}{0ex}}\mathit{heat}\phantom{\rule{0.147em}{0ex}}\mathit{energy}\phantom{\rule{0.147em}{0ex}}\mathit{required}\phantom{\rule{0.147em}{0ex}}(Q)}{\mathit{Raise}\phantom{\rule{0.147em}{0ex}}\mathit{in}\phantom{\rule{0.147em}{0ex}}\mathit{Temperature}\phantom{\rule{0.147em}{0ex}}(\mathrm{\Delta}T)}$

${C}^{\prime}=\frac{Q}{\mathrm{\Delta}T}$

The unit of heat capacity is \(cal / °C\). In an SI system, it is measured in ${\mathit{JK}}^{-1}$

Specific Heat:

When the heat capacity of a substance is expressed for unit mass, it is called specific heat capacity.

The specific heat capacity of a substance is defined as the amount of heat energy required to raise the temperature of \(1 kilogram \)of a substance by \(1 °C\) or \(1 K\). It is denoted by the symbol C.

$\mathit{Specific}\phantom{\rule{0.147em}{0ex}}\mathit{heat}\phantom{\rule{0.147em}{0ex}}\mathit{capacity}\phantom{\rule{0.147em}{0ex}}=\frac{\mathit{Amount}\phantom{\rule{0.147em}{0ex}}\mathit{of}\phantom{\rule{0.147em}{0ex}}\mathit{heat}\phantom{\rule{0.147em}{0ex}}\mathit{energy}\phantom{\rule{0.147em}{0ex}}\mathit{required}(Q)}{\mathit{Mass}\phantom{\rule{0.147em}{0ex}}(m)\times \mathit{Raise}\phantom{\rule{0.147em}{0ex}}\mathit{in}\phantom{\rule{0.147em}{0ex}}\mathit{temperature}(\mathrm{\Delta}T)}$

$C=\frac{Q}{m\times \mathrm{\Delta}T}$

The SI unit of specific heat capacity is $J.{\mathit{Kg}}^{-1}.{K}^{-1}$