Learning objective

Recognize that the change in thermal energy during a reaction is termed the enthalpy change (H), where H is negative for exothermic reactions and positive for endothermic reactions.

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Cambridge IGCSE ChemistryChemical energeticsSupplement content

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Recognize that the change in thermal energy during a reaction is termed the enthalpy change (H), where H is negative for exothermic reactions and positive for endothermic reactions

This point belongs to Exothermic and endothermic reactions, especially Exothermic and endothermic reactions outcomes.
You need to be able to recognize that the change in thermal energy during a reaction is termed the enthalpy change (H), where H is negative for exothermic reactions and positive for endothermic reactions.
The key ideas to know are State.
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This objective helps connect Exothermic and endothermic reactions outcomes to exam-style questions, flashcards, and revision notes for Exothermic and endothermic reactions.

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Paper 4 structured question: Exothermic and endothermic reactions

Paper 4Theory (Extended)1 marks

Description

Enthalpy Changes in Reactions

Consider the following reactions: 1) Combustion of methane, 2) Dissolving ammonium chloride in water. Identify the type of enthalpy change for each reaction.

a
State the type of enthalpy change for the combustion of methane.
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Related learning objectives

Identify that an exothermic reaction releases thermal energy to the environment, resulting in a rise in the temperature of the surroundings.
Exothermic and endothermic reactions outcomes
Identify that an endothermic reaction absorbs thermal energy from the environment, causing a drop in the temperature of the surroundings.
Exothermic and endothermic reactions outcomes
Analyze reaction pathway diagrams that illustrate both exothermic and endothermic reactions.
Exothermic and endothermic reactions outcomes
Define activation energy (Ea) as the minimum energy required for colliding particles to undergo a reaction.
Exothermic and endothermic reactions outcomes
Create and label reaction pathway diagrams for exothermic and endothermic reactions based on provided information, including reactants, products, enthalpy change (H), and activation energy (Ea).
Exothermic and endothermic reactions outcomes

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