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: Understand heat - transfer principle

Heat flows from a hotter object to a colder object until thermal equilibrium is reached. In an insulated system, the total heat energy is conserved. The temperature of the colder object will increase and the temperature of the hotter object will decrease.

Step2: Analyze each option

• Option 1: Block 2 temperature remains the same ($93^{\circ}C$) and Block 1 temperature increases to $85^{\circ}C$. But heat transfer should cause Block 2's temperature to decrease, so this is incorrect.
• Option 2: Block 1 has a higher temperature ($88^{\circ}C$) than Block 2 ($87^{\circ}C$) after heat - transfer started with Block 2 being hotter initially. This is incorrect as heat should flow from Block 2 to Block 1.
• Option 3: Block 1's temperature increases from $82^{\circ}C$ to $84^{\circ}C$ and Block 2's temperature decreases from $93^{\circ}C$ to $91^{\circ}C$. This is consistent with heat flowing from the hotter Block 2 to the colder Block 1.
• Option 4: Block 2's temperature increases to $100^{\circ}C$ while Block 1's temperature increases to $89^{\circ}C$. But since the system is insulated and Block 2 was initially the hotter one, its temperature should not increase further. This is incorrect.

Answer:

Block 1: $84^{\circ}C$, Block 2: $91^{\circ}C$ (the pair in the third option)