How much joules of heat are given out when a piece of iron, of mass 60g and specific heat capacity 460JKg$^{-1}$K$^{-1}$, cools from 75ºC to 35ºC

1. Analyze the Question

We are asked to calculate the quantity of heat energy released ($Q$) by a piece of iron as it cools down. We are given:

• Mass ($m$) = 60g
• Specific heat capacity ($c$) = 460 J kg⁻¹ K⁻¹
• Initial temperature ($T_1$) = 75ºC
• Final temperature ($T_2$) = 35ºC

2. Explain the Concept

The amount of heat energy lost or gained by a substance is calculated using the formula:

Where:

• $m$ is the mass in kilograms (kg).
• $c$ is the specific heat capacity.
• $\Delta\theta$ is the change in temperature ($T_1 - T_2$).

Important Note: Always ensure the mass is in kilograms (SI unit) to match the specific heat capacity unit (J kg⁻¹ K⁻¹).

3. Show the Solution

Step 1: Convert mass to kilograms

Step 2: Calculate the change in temperature ($\Delta\theta$)

Step 3: Calculate the heat energy ($Q$)

4. Identify the Answer

Comparing our result to the given options, the calculated value is 1104J, which corresponds to option D.

5. Exam Tip

In physics calculations, unit consistency is key. Many students lose marks because they forget to convert grams to kilograms. Always check if your mass is in grams; if it is, divide by 1000 immediately before plugging it into your formula!