Question

Two metal blocks that have slightly different temperatures are placed next to one another. After five minutes, they both have lower but equal temperatures. According to the law of conservation of energy, what most likely happened?
Energy was created inside the blocks.
Energy was destroyed inside the blocks.
Energy was absorbed into the blocks from outside the system.
Energy was transferred from the warmer block to the cooler block.

Answer 1

Energy was transferred from the warmer block to the cooler block.

Heat flows from hot to cold until thermal equilibrium is reached. The fact both ended up cooler also implies some heat was lost to the surroundings, but no energy was created or destroyed.