Question

6 what is true of two objects at the same temperature? a they have the same number of molecules b their molecules stop moving c their molecules move at the same average speed d heat transfer between the two objects stops

Explanation:

• Option A: The number of molecules depends on the amount of substance (moles) and not directly on temperature. Different substances at the same temperature can have different numbers of molecules. Eliminate A.
• Option B: Molecules are always in motion (kinetic theory of matter), even at absolute zero (theoretical), and at the same temperature, molecules still move (with average kinetic energy related to temperature). Eliminate B.
• Option C: Average speed of molecules depends on both temperature and molar mass (since \( KE=\frac{1}{2}mv^{2} \) and \( KE \propto T \)). Different substances (different molar masses) at the same temperature will have different average speeds. Eliminate C.
• Option D: Heat transfer occurs due to temperature difference. If two objects are at the same temperature, there is no net heat transfer between them (thermal equilibrium). This is correct.

Answer:

D. Heat transfer between the two objects stops