Question

1. find the heat energy required to raise an iron bar of mass 2.0 kg from 20°c to 120°c.

Explanation:

Step1: Recall the formula for heat energy

The formula for heat energy \( Q \) required to change the temperature of a substance is \( Q = mc\Delta T \), where \( m \) is the mass, \( c \) is the specific heat capacity, and \( \Delta T \) is the change in temperature. For iron, the specific heat capacity \( c = 450 \, \text{J/(kg·°C)} \).

Step2: Calculate the change in temperature

The initial temperature \( T_1 = 20^\circ\text{C} \) and the final temperature \( T_2 = 120^\circ\text{C} \). So, \( \Delta T = T_2 - T_1 = 120 - 20 = 100^\circ\text{C} \).

Step3: Substitute values into the formula

Given \( m = 2.0 \, \text{kg} \), \( c = 450 \, \text{J/(kg·°C)} \), and \( \Delta T = 100^\circ\text{C} \). Substitute these into \( Q = mc\Delta T \):
\( Q = 2.0 \times 450 \times 100 \)
\( Q = 2.0 \times 45000 \)
\( Q = 90000 \, \text{J} \) or \( 9.0 \times 10^4 \, \text{J} \)

Answer:

The heat energy required is \( 90000 \, \text{J} \) (or \( 9.0 \times 10^4 \, \text{J} \)).