Question

100°c block 1, 60°c block 2. later, the temperature of each block is measured again. which pair of temperatures is possible? four options: block 1 80°c, block 2 40°c; block 1 90°c, block 2 80°c; block 1 120°c, block 2 80°c; block 1 80°c, block 2 90°c

Explanation:

Step1: Recall heat transfer principle

Heat flows from higher temp to lower temp until thermal equilibrium. Initial temps: Block 1 = \(100^\circ\text{C}\), Block 2 = \(60^\circ\text{C}\). So Block 1 cools, Block 2 warms. Final temps: Block 1 < \(100^\circ\text{C}\), Block 2 > \(60^\circ\text{C}\), and Block 1 ≥ Block 2 (at equilibrium, equal; before, Block 1 still higher or equal).

Step2: Analyze each option

• Option 1: \(80^\circ\text{C}\) (Block1), \(40^\circ\text{C}\) (Block2). Block2 temp decreased (violates, should increase). Reject.
• Option 2: \(90^\circ\text{C}\) (Block1), \(80^\circ\text{C}\) (Block2). Block1 cooled (\(100 \to 90\)), Block2 warmed (\(60 \to 80\)), and \(90 \geq 80\). Valid.
• Option 3: \(105^\circ\text{C}\) (Block1). Block1 can't heat up (no heat source). Reject.
• Option 4: \(60^\circ\text{C}\) (Block1), \(90^\circ\text{C}\) (Block2). Block1 temp lower than Block2 (heat can't flow from lower to higher spontaneously). Reject.

Answer:

\(90^\circ\text{C}\) (Block 1) and \(80^\circ\text{C}\) (Block 2) (the second option)