Study the given table. a. If equal mass of these objects are heated to the same temperature and exposed in air, which one cools the fastest and why?

Specific heat capacity is the amount of heat energy required to raise the temperature of 1 kg of a substance by $1^\circ\text{C}$. A substance with a lower specific heat capacity requires less energy to change its temperature.

Substance C has the lowest specific heat capacity ($380 \text{ J/kg}^\circ\text{C}$) compared to Substance B ($460 \text{ J/kg}^\circ\text{C}$) and Substance A ($900 \text{ J/kg}^\circ\text{C}$).

A substance with a lower specific heat capacity will lose heat energy more quickly for a given temperature drop when exposed to cooler surroundings. Therefore, it will cool down faster.

• Answer: Substance C cools the fastest.
• Reason: Substance C has the lowest specific heat capacity. This means it stores less heat energy per unit mass per degree Celsius change in temperature, and thus loses its stored heat more rapidly to the surroundings, leading to faster cooling.

• Mass of substance A ($m$) = $20 \text{ kg}$
• Change in temperature ($\Delta T$) = $50^\circ\text{C}$
• Specific heat capacity of substance A ($c_A$) = $900 \text{ J/kg}^\circ\text{C}$ (from the table)

The amount of heat energy ($Q$) supplied is given by the formula:

• Answer: The heat energy to be supplied is $\boxed{900000 \text{ J}}$ (or $900 \text{ kJ}$).