Question

two identical blocks are heated to different temperatures. the blocks are placed so that they touch, and heat begins to flow between the blocks. the pair of blocks is insulated, so no energy escapes. later, the temperature of each block is measured again. which pair of temperatures is possible?

Explanation:

Step1: Recall heat - transfer principle

Heat flows from a higher - temperature object to a lower - temperature object until thermal equilibrium is reached. The initial temperatures are $T_1 = 61^{\circ}C$ and $T_2=106^{\circ}C$. So, the temperature of Block 1 should increase and the temperature of Block 2 should decrease.

Step2: Analyze each option

• Option 1: Block 1 remains at $61^{\circ}C$, which is not possible as heat should flow to it.
• Option 2: Both temperatures increase compared to the initial state, which is not possible as there is no external heat source.
• Option 3: Block 1 has a higher temperature than Block 2 after heat transfer, which is against the direction of heat flow (heat should flow from Block 2 to Block 1 initially).
• Option 4: Block 1's temperature ($83^{\circ}C$) is higher than its initial temperature ($61^{\circ}C$) and Block 2's temperature ($84^{\circ}C$) is lower than its initial temperature ($106^{\circ}C$), which is consistent with heat - transfer principles.

Answer:

The pair of temperatures in the fourth option (Block 1: $83^{\circ}C$, Block 2: $84^{\circ}C$) is possible.