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Chemical Energy
Revision for Year 8 Text
| Question | Answer |
|---|---|
| Are chemical changes reversible or not reversible? | Not reversible. |
| Are physical changes reversible or not reversible? | Reversible. |
| What is a chemical reaction? | When reactions occur, the atoms change partners and new bonds form. |
| What energy is being used to hold the atoms together in molecules? | Chemical Energy |
| What is an endothermic reaction? | A reaction in which heat energy is “absorbed” from the surrounding air |
| What is an exothermic reaction? | Areaction that “releases” energy in the form of heat & sometimes light into the air. |
| What happens to the temperature of an exothermic reaction? | It increases. |
| What happens to the temperature of an endothermic reaction? | It decreases. |
| Do breaking chemical bonds take in energy or give out energy? | They take in energy. |
| Is the breaking of chemical bonds endothermic or exothermic? | Endothermic. |
| Breaking bonds takes in or gives out energy? | Takes in. |
| Does forming new bonds take in or give out energy? | Gives out energy = exothermic. |
| What do catalysts do? | They speed up a chemical reaction. |
| Are catalysts used up in a reaction? | No |
| What is activation energy? | This is the energy needed to start a chemical reaction. |
| How do most catalysts work? | They lower the reactions activation energy. This lowers the amount of energy needed for the reaction to proceed and helps reactions occur faster. |
| What is a biological catalyst called? | An enzyme. |
| Give another definition of a chemical reaction. | The process of rearrangement of two or more molecules to form new substances. |
| Describe two advantages of using catalysts. | Catalysts speed up the rate of reaction, which saves money Catalysts allow the reaction to work at a much lower temperature. This reduces the energy used up in a reaction which is good for sustainable development. |
| What are some disadvantages of using catalysts? | They are very expensive to buy. They often need to be removed from a product and cleaned. Different reactions use different catalysts. Catalysts can be ruined by impurities, so they stop working |
Created by:
Highcliffe Science
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