Energy Transfer with Reactions
Subjects / Core Science / Edexcel GCSE Science
Everyone knows that a ball runs downhill until it reaches a big enough obstacle to stop it, or a pencil can rest on a tabletop but could lose energy by falling to the floor. These observations are obvious in everyday life, but harder to explain in terms of chemistry. First, we need to understand about endothermic and exothermic changes. Endothermic changes have heat supplied to the chemicals in a reaction, whereas exothermic ones have heat released from the chemicals. Calorimetry is the science of measuring the heat transfer in a chemical reaction. We will look at combustion as a source of heat energy, and find out why some burning reactions cause explosions and why some just glow gently. Flammability can be useful but also dangerous, so we will conclude this title with a consideration of hazard symbols.
| Author: | Mike Ryan | Publisher: | GCSEPod® |
| Narrator: | Pauline Addis | ISBN: | 978-1-84906-286-2 |
| Video ISBN: | 978-1-84906-786-7 |
Chapters
- Endothermic and Exothermic Changes
- Calorimetry
- Fire and Combustion
- Burning Fuels and Flammability
- Energy Changes During a Reaction
- Complete and Incomplete Combustion
- Hazard Symbols
Exam Board Relevance
- Edxcel
- AQA
- CEA
- IGCSE (EdExcel)
- OCR
- SQA
- WJEC
- IGCSE (CiE)
Includes original GCSEPod image art. Additional pictorial images created by Damon Smith
Curriculum and Exam Board Information
Key Issues
Titles
Chapters
- An endothermic reaction is one that takes energy, often as heat, from the surroundings
- An exothermic reaction is one that transfers energy, often as heat, to the surroundings
- Bond making, bond breaking and energy changes during reactions
- Changes in temperature often accompany reactions
- Endothermic Reactions
- Endothermic reactions include thermal decompositions
- Examples of exothermic reactions include combustion, may oxidation reactions and neutralisation
- Exothermic and endothermic reactions
- Exothermic Reactions
- Gaseous Reactions
- give and recognise examples of simple exothermic and endothermic reactions, e.g. combustion
- give and recognise examples of simple exothermic and endothermic reactions, e.g. displacement
- give and recognise examples of simple exothermic and endothermic reactions, e.g. dissolving
- give and recognise examples of simple exothermic and endothermic reactions, e.g. hydration of CuSO4
- give and recognise examples of simple exothermic and endothermic reactions, e.g. neutralisation
- give and recognise examples of simple exothermic and endothermic reactions, e.g. photosynthesis
- If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction
- If the temperature is lowered, the yield from the endothermic reaction decreases and the yield from the exothermic reaction increases
- If the temperature is raised, the yield from the endothermic reaction increases and the yield from the exothermic reaction decreases
- In gaseous reactions, an increase in pressure will favour the reaction that produced the least number of molecules as shown by the symbol equation for that reaction
- In some chemical reactions, the products of the reaction can react to produce the original reactants
- Industrial Processes
- It is important for sustainable development as well as economic reasons to minimise energy requirements and energy wasted in industrial processes
- Lowering the Temperature
- Non-vigorous conditions mean less energy is used and less is released into the environment
- Raising the Temperature
- recognise and know the value of common hazard symbols on containers, i.e. flammable, toxic, corrosive, explosive, harmful/irritant
- recognise that the energy transferred in a chemical reaction is associated with breaking and making of chemical bonds
- Reversible Reactions
- Such reactions are called reversible reactions
- The relative amounts of all the reacting substances in equilibrium depend on the conditions of the reaction
- The reverse reaction can be used to test for water
- The same amount of energy is transferred in each case
- The Transfer of Energy
- These factors, together with reaction rates, are important when determining the optimum conditions in industrial processes, including the Haber process
- When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction
- When chemical reactions occur energy is transferred to or from the surroundings
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