C3.2 - Energetics Flashcards
What is an exothermic reaction ?
A reaction that gives out heat energy to the surroundings, causing the temperature to increase
What is an endothermic reaction ?
A reaction that takes in the heat energy from the surroundings, causing the temperature to decrease
What are some examples of exothermic reactions ?
- Combustion ( burning )
- Neutralisation ( acid + alkali )
- Metal + acid
- Displacement reactions
What are some examples of endothermic reactions ?
- Decomposition reactions
- Acid + hydrogen carbonates ( including Herbert )
- Photosynthesis
Draw the endothermic reactions graph ?
Draw the exothermic reactions graph ?
What is the energy change equation ?
Energy Change = break - make
How to check whatever a reaction is end-exothermic ?
- By measuring the start and end temperature
- By calculating make and break
What is the energy change for exothermic reactions ?
Exothermic reactions release energy to the surroundings so they have a negative energy change
What is the energy change for endothermic reactions ?
Exothermic reactions absorb energy to the surroundings so they have a positive energy change
Why is the energy change in endothermic reactions positive?
The products have more energy than the reactants , so the energy change is positive.
Why is the energy change in exothermic reactions negative ?
The products have less chemical energy than reactants. Therefore the energy change is negative.
How is energy used to break/make bonds in exothermic reaction ?
If the reaction is exothermic more energy is released making bonds in products than is needed to break bonds in reactants
How is energy used to break/make bonds in endothermic reaction ?
If the reaction is endothermic then more energy is needed to break bonds in reactants than is released making bonds in products
