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C5
| Question | Answer |
|---|---|
| What is the law for conservation of energy | Energy cannot be created or destroyed only transferred |
| Describe an exothermic reaction | Transfers energy to its surroundings |
| Describe endothermic reactions | Takes energy in from surroundings |
| Give 2 examples of exothermic reactions | Respiration and combustion |
| Give 2 examples of endothermic reactions | Photosynthesis and electrolysis |
| What is activation energy | The energy required for a reaction to take place |
| What must happen for particles to react | They must collide and the activation energy must be reached |
| How would you calculate bond energies | 1. Balance formula 2. Draw diagrams 3. Write energy for each bond 4. Multiply energy for each bond 5. Total energies for breaking and making 6. Bonds made - bonds broken |
| How do you make a simple cell | Connect 2 different metals in contact with an electrode |
| What do cells contain | Chemicals which react to produce electricity |
| What factors affect the voltage produced by a cell | Type of electrode and electrolyte |
| What is the difference between rechargeable and non rechargeable cells | The reaction in a rechargeable cell can be reversed by inputting energy |
| Alkaline batteries are... | Non rechargeable |
| Why do non rechargeable cells and batteries stop working | The reaction is non reversable |
| How is a rechargeable cell recharged | Reversing the reaction |
| What is a battery | Two or more cells connected in series |
| Describe how a fuel cell works in terms of oxidation | Hydrogen is oxidised and the negative electrons produce current |
| Write a half equation for the reaction at the positive electrode inva hydrogen fuel cell | 4H+ + 4e- +2O2 -> H2O |
| Write a half equation for the reaction at the negative electrode in a hydrogen fuel cell | H2 - 2e- -> 2H+ |
| What are the advantages of hydrogen fuel cells | -less pollutants -cheaper -batteries can only be recharged a certain number of times -batteries store less energy |
| What are the disadvantages of hydrogen fuel cells | -gas takes up more space -explosive so hard to store -often made from hydrocarbons so pollution |
| What is an anomaly |
Created by:
Liam P
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