C7 Energy Changes
- Created by: Luke Newton1
- Created on: 07-04-18 14:55
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- Energy Changes
- C7.1 Exothermic and Endothermic Reactions
- Energy is conserved in chemical reactions. It is neither created nor destroyed
- A reaction in which energy is transferred from reacting substances to their surroundings is called an exothermic reaction
- A reaction in which energy is transferred to the reacting substances from their surroundings is called an endothermic reaction
- C7.2 Using Energy Transfer From Reactions
- Exothermic changes can be used in hand warmers and self-heating cans.
- Endothermic changes can be used in instant cold packs for sport injuries.
- C7.3 Reaction Profiles
- You can show the relative difference in the energy of reactants and products on reaction profiles
- Bond breaking is endothermic, whereas bond making is exothermic
- C7.4 Bond Energy Calculations
- Energy must be supplies to break the bonds between atoms and reactants
- When new bonds form energy is released
- In an exothermic reaction, the energy released when new bonds are formed is greater than the energy required to break the bonds
- In an endothermic reaction, the energy released when new bonds are formed is less than the energy need when bonds are broken
- You can calculate the overall energy change in a chemical reaction using bond energies
- C7.5 Chemical Cells & Batteries
- Metals tend to los electrons and form positive ions
- When two metals are dipped in a solid solution and joined to a wire, the more reactive metal will donate electrons to the less reactive metal, this forms a simple electrical cell
- The greater the difference in reactivity the higher the voltage produced
- C7.6 Fuel Cells
- Much of the world relies on fossil fuels. However, they are non-renewable and they cause pollution
- Hydrogen is one alternative fuel. It can be burnt in combustion engines or used in fuel cells to power vehicles
- Hydrogen gas ix oxidised and provides a source of electrons in the hydrogen fuel cell in which the only waste product is water.
- C7.1 Exothermic and Endothermic Reactions
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