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Explain what is meant by an endothermic reaction.
See it on the paper →The boiling point of a sample of water is 102 °C at standard atmospheric pressure. Explain how this shows that the sample of water is impure.
See it on the paper →Explain why pure water is a poor conductor of electricity.
See it on the paper →Cracking is an endothermic reaction. State what is meant by an endothermic reaction.
See it on the paper →The decomposition of calcium carbonate to calcium oxide is an endothermic reaction. State the meaning of the term endothermic.
See it on the paper →When ethene reacts with bromine the reaction is exothermic. Explain why the reaction of ethene and bromine is exothermic. Use ideas about bond breaking and bond making.
See it on the paper →This reaction is an exothermic reaction. State what is meant by an exothermic reaction.
See it on the paper →The conversion of calcium carbonate to calcium oxide involves an endothermic chemical reaction. State the meaning of the term endothermic.
Not all candidates identified that it is the lack of free moving electrons or ions that makes water a poor conductor. A fairly common misconception is that it does not contain a metal.
— Examiner report, May/June 2025, 0654/41 Q5(e)(ii) (Cambridge)
Many candidates had a very good idea what endothermic meant and described it clearly.
— Examiner report, May/June 2023, 0654/33 Q11(b)(iii) (Cambridge)
Many candidates were able to state that energy is released during exothermic reactions, however very few were able to apply this to the context of the question. Candidates were required to link energy being taken in to bond breaking and energy being given out to bond making. However, often explanations only included one of these points. Very few candidates were able to give a full explanation stat...
— Examiner report, October/November 2021, 0654/43 Q2(d)(ii) (Cambridge)
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Calcium oxide and carbon dioxide are simpler substances than calcium carbonate. State the type of chemical reaction that converts calcium carbonate to calcium oxide in the lime kiln.
See it on the paper →In process B, larger molecules are changed into smaller molecules. The energy level diagram for this reaction is shown in Fig. 2.2. smaller molecules energy larger molecules progress of reaction Fig 2.2 State the type of chemical reaction that causes the type of energy change shown in Fig. 2.2. Explain your answer in t...
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