C7 - Energy Changes Flashcards
Where is energy conserved?
- In chemical reactions, it is neither created nor destroyed.
What is an exothermic reaction?
A reaction in which energy is transferred from the reacting substances to their surroundings.
What is an endothermic reaction?
A reaction in which energy is transferred to the reacting substances from their surroundings.
Where can exothermic changes be used?
In hand warmers and self heating cans, crystallisation of a supersaturated solution is used in reusable warmers.
However disposable, one-off warmers heat up the surroundings for longer.
Where can endothermic changes be used?
Instant cold packs for sports injuries.
How can you show the relative difference in the energy of reactants and products?
- On reaction profiles.
What is bond breaking?
- Endothermic.
What is bond making?
- Exothermic.
What must energy be like in chemical reactions?
- Energy must be supplied to break the bonds between atoms in the reactants.
What happens when new bonds are formed between atoms in a chemical reaction?
Energy is released.
What happens during an exothermic reaction?
The energy is released when new bonds are formed is greater than the energy absorbed when the bonds are broken.
What happens during an endothermic reaction?
The energy released when new bonds are formed is less than the energy absorbed when bonds are broken.
How can you calculate the overall energy change in chemical reaction?
Using bond energies.
