What distinguishes endothermic from exothermic reactions, and give an example of each.

• A. Endothermic releases heat; example: melting ice.
• B. Endothermic absorbs heat; example: melting ice; Exothermic releases heat; example: combustion.
• C. Endothermic absorbs heat; example: condensation; Exothermic releases heat; example: freezing.
• D. Endothermic releases heat; example: photosynthesis; Exothermic absorbs heat; example: boiling water.

Answer: (B)

End temperature changes tell you whether a reaction is endothermic or exothermic: endothermic reactions absorb heat from their surroundings, making the surroundings feel cooler, while exothermic reactions release heat to the surroundings, warming them. The right choice states that endothermic processes absorb heat and gives melting ice as an example, which is correct because melting requires energy input to break the solid structure. It also says exothermic processes release heat and gives combustion as an example, which is true because burning releases energy as heat and light.

The other options mix up the heat flow or use examples that don’t fit. For instance, condensation actually releases heat, not absorbs, so using it as an endothermic example is incorrect. Freezing releases heat, so pairing it with exothermic is misleading in that sense. And boiling water is an endothermic process, so pairing it with exothermic is incorrect.