Grade 9 students at King’s Schools explored this question in a hands-on chemistry experiment. A change in temperature provided a clue. When a reaction releases heat, the surroundings warm up. When a reaction absorbs heat, the surroundings cool down.
Students connected these observations to what happens between atoms. Breaking chemical bonds takes energy, while forming new bonds releases energy. The balance between the two explains why some reactions release heat overall (exothermic reactions) and others absorb it (endothermic reactions).
