Question

How much heat is required to raise the temperature of $150g$ of iron ${20^\circ}C$ to ${25^\circ}C$? (Specific heat of iron $480Jk{g^{ - 1}}{}^\circ{C^{ - 1}}$)

Answer 1

Specific heat- The specific heat of a given substance is defined as the amount of heat is supplied to raise the temperature of a unit mass of the substance by ${1^\circ}C$.
If an amount of $\Delta Q$ of heat is given to a mass m of the substance and its temperature rises by $\Delta T$, then the specific heat capacity S is given by the equation:
$s = \dfrac{{\Delta Q}}{{m\Delta T}}$

Complete step by step answer:
Given:-
Mass of the iron, m = 150g = 0.15kg
Specific heat of iron, $s$ = $480Jk{g^{ - 1}}{}^\circ{C^{ - 1}}$
Initial temperature ${T_i} = {20^\circ}C$
Final temperature ${T_f} = {25^\circ}C$
Now, Change in temperature $\Delta T = {T_f} - {T_i} = {5^\circ}C$
The amount of heat supplied is given as $\Delta Q = ms\Delta T$……………………… (i)
Now, substituting the given values in the above equation, we get
$\Rightarrow \Delta Q = (0.15 \times 480 \times 5)J$
$\therefore \Delta Q = 360J$

Hence, the heat is required to raise the temperature of $150g$ of iron ${20^\circ}C$ to ${25^\circ} C$ is 360 J.

Note: Specific heat of a substance is very important it gives an indication of how much energy will be required to heat or cool an object of a given mass by a given amount. This will give us information as to how long the heating or cooling process will take under a given supply, as well as the cost implications. A high specific heat of a substance means that an amount of heat is required to raise the temperature of the substance. It is often seen that the students get confused with heat capacity and specific heat capacity of a substance. Heat capacity of a substance is the amount of heat is required to raise the temperature of a substance by ${1^\circ}C$ while Specific heat capacity of a substance is the amount of heat is required to raise unit mass of a substance by ${1^\circ}C$.