Question

Which of the following are true statements? 
I. The heat capacity of a substance is the amount of heat that substance can hold per unit of temperature. 
II. The specific heat for a single substance is the same for all phases of that substance. 
III. When heat is added to a fluid, its temperature will change less if it is allowed to expand.

• A. Only I
• B. Only III
• C. I and III
• D. All of these

Hint:

Specific heat varies depending on the phase of a substance, so always check if the substance is in solid, liquid, or gas form when considering its specific heat.

Answer 1

The Correct Option is C

- Statement I is true because the heat capacity of a substance is defined as the amount of heat required to raise the temperature of the substance by one degree Celsius (or one Kelvin). It is an extensive property and depends on the quantity of the substance.

- Statement II is false because specific heat depends not only on the substance but also on its phase (solid, liquid, or gas). For example, the specific heat of water in its liquid form is different from its specific heat when it is in the solid state (ice) or in the gas state (steam). Therefore, the phase of the substance must be considered when discussing specific heat.

- Statement III is true because when a substance undergoes expansion, the heat is spread over a larger volume, which leads to a smaller increase in temperature. This occurs because the energy required to increase the temperature is distributed over a greater number of particles or volume.

Therefore, the correct answer is (c) I and III.