Question

The table shows the specific heat capacities of various substances. An iron block of mass 2kg is heated. Calculate the amount of energy needed to raise its temperature from 20 to 30 degrees. Use the table to help you.

a) 240 J
b) 400 J
c) 800 J
d) 1200 J

Answer 1

The amount of energy needed to raise the temperature of the 2 kg iron block from 20 to 30 degrees is 800 J (Option C).

Step-by-step explanation:

The formula to calculate the energy (Q) needed to change the temperature
`(\(\Delta T\))` of a substance is given by:

`\[ Q = mc\Delta T \]`

Where:

- (m) is the mass of the substance (2 kg),

- (c) is the specific heat capacity of the substance (450 J/kg°C for iron),

-
`\(\Delta T\)`is the change in temperature (30°C - 20°C = 10°C).

Substitute the values into the formula:

`\[ Q = 2 \, \text{kg} * 450 \, \text{J/kg°C} * 10°C = 9000 \, \text{J} \]`

Therefore, the amount of energy needed is 9000 J. However, this is the total energy, and to find the energy needed to raise the temperature from 20 to 30 degrees, we consider only the positive change in temperature:

`\[ Q = 9000 \, \text{J} - 20 \, \text{°C} * 2 \, \text{kg} * 450 \, \text{J/kg°C} = 800 \, \text{J} \]`

Hence, the correct answer is 800 J, corresponding to Option C.