AQA · Chemistry · 8462
GCSE Chemistry (AQA): Exothermic & Endothermic Reactions
Topic 4 — Chemical Changes. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Exothermic & Endothermic Reactions - Reaction Profiles | Activation Energy"; each card deep-links to the moment in the video it came from. Lesson 5.01 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_5.01.
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Why does an exothermic reaction still need an input of energy to start?
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The particles must first reach the activation energy before they can collide successfully and react, even though energy is released overall.
Energy cannot be created or destroyed, only ? from one place to another.
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transferred
What temperature change would you measure in a sealed container during an exothermic reaction?
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An increase in temperature, as heat energy is released to the surroundings.
Is the neutralisation of an acid by a base exothermic or endothermic?
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Exothermic — it releases energy to the surroundings.
On a reaction profile, where are the products drawn for an endothermic reaction?
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Higher than the reactants, because they store more energy.
What do the axes of a reaction profile represent?
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The y-axis is the total energy of the molecules; the x-axis is the progress of the reaction.
On a reaction profile, where are the products drawn for an exothermic reaction?
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Lower than the reactants, because they store less energy.
What is an exothermic reaction?
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A reaction that transfers energy to the surroundings, usually as heat, so the products store less energy than the reactants.
Which type of reaction is the most common example of an exothermic reaction?
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Combustion, in which fuels are burned, usually in the presence of oxygen.
Define activation energy.
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The minimum amount of energy reactant particles need in order to collide with each other and react.
What is an endothermic reaction?
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A reaction that takes in energy from the surroundings, usually as heat, so the products store more energy than the reactants.
How is activation energy shown on a reaction profile?
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As the energy difference between the reactants' energy level and the highest point of the curve.
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