Chapter 5, Problem 44R

To determine

The energy needed to raise the temperature of $4\text{ kg}$ of water.

Answer to Problem 44R

  $Q=840\text{kJ}$

Explanation of Solution

Given:

Mass, $m=4\text{ kg}$

Final temperature, $T_2={75}^o\text{C}$

Initial temperature, $T_1={25}^o\text{C}$

Heat capacity of water, $c_w=4200{\text{J/kg}}^o\text{C}$

Formula used:

Thermal energy can be calculated as:

  $Q=m{c}_w\left(\Delta T\right)$

Where,

  $m$ = mass

  $c_w$ = Heat capacity of water

  $\left(\Delta T\right)$ = change in temperature

Calculation:

Plugging the values

  $\begin{array}{l}Q=4\times 4200\times \left(75-25\right)\\ Q=840\text{kJ}\end{array}$

Conclusion:

Required thermal energy is $Q=840\text{kJ}$ .