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SingaporeCombined ScienceQuick questions
Chemistry: Reactions, Acids and Salts
Quick questions on Exothermic and endothermic reactions explained: O-Level Combined Science
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is activation energy?Show answer
Even an exothermic reaction usually needs an initial input of energy to start, to break the first bonds. This minimum energy is the activation energy. It is why a fuel needs a spark to ignite, even though burning then releases far more energy than the spark supplied.
What are energy level diagrams?Show answer
An energy level diagram plots energy (vertical axis) against the progress of the reaction (horizontal axis):
What is q1?Show answer
State whether neutralisation is exothermic or endothermic and what happens to the temperature of the mixture. [2 marks]
What is q2?Show answer
Explain, in terms of bonds, why a reaction is endothermic. [2 marks]
What is q3?Show answer
On an energy level diagram for an exothermic reaction, state where the products lie relative to the reactants and what the hump represents. [2 marks]
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