Why do reactions either give out or absorb heat?
2 marks · HardDescribe, in terms of bonds and energy, what happens during an endothermic reaction.
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Also accept: The energy required to break bonds is greater than the energy released when bonds are made
Common mistakes: Saying energy is given out overall; Confusing bond breaking and making
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Marking points
M1 · 1 mark · Explains or states that breaking bonds absorbs (requires) energy
A1 · 1 mark · States that, in an endothermic reaction, more energy is needed to break bonds than is released when new bonds are formed
Worked solution
Breaking bonds in the reactants needs energy (absorbs energy from surroundings).
In an endothermic reaction, the energy needed to break bonds is greater than the energy released by making bonds in the products.