Year 10 - Science
Breaking and making bonds: using bond energies
Energy changes in reactions
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit covers bulk material properties related to bonding and intermolecular forces and explores bond breaking, bond making, activation energy, and reaction profiles. It focuses on selecting appropriate techniques, translating data, and presenting observations using various models.
Lesson Summary
You will learn to describe how bond making and breaking use or release energy, and use bond energies to calculate whether a reaction is exothermic or endothermic.
Key Notes
- The energy needed to break bonds and the energy released when bonds are formed can be calculated from bond energies.
- The difference between the energy needed to break bonds and the energy released is the overall energy change.
Vocabulary To Learn
- endothermic: An endothermic chemical reaction is a type of reaction in which energy is transferred from the surroundings to the products, e.g. photosynthesis.
- exothermic: An exothermic chemical reaction is a type of reaction in which energy is transferred from the reactants to the surroundings, e.g. combustion.
- activation energy: The minimum energy that the particles must have in order to react is known as the activation energy.
- bond energy: The energy required to break a covalent bond, or released when making a covalent bond. is known as the bond energy.
Common Mistakes To Avoid
- Pupils often make mistakes when identifying the different types of bonds and the number of each in a molecule. They may also reverse the calculation of the overall energy change, as make - break.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
The energy needed to break bonds and the energy released when bonds are formed can be calculated from bond energies. The difference between the energy needed to break bonds and the energy released is the overall energy change.
2. Define this scientific word and use it in context. 'endothermic'
An endothermic chemical reaction is a type of reaction in which energy is transferred from the surroundings to the products, e.g. photosynthesis. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: Pupils often make mistakes when identifying the different types of bonds and the number of each in a molecule. They may also reverse the calculation of the overall energy change, as make - break. Correction: Molecules can be complex and should be drawn to show all the bonds. Emphasis that double and triple covalent bonds are different to single bonds. Pupils should be instructed to consider whether a reaction is exothermic or endothermic.
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