P1 - Energy Changes Flashcards
1
Q
Define an exothermic reaction
A
Energy is transferred to the surroundings. Usually through heating.
Example: combustion, neutralisation reactions, oxidation reactions
2
Q
Define an endothermic reaction
A
Energy is taken in from the surroundings. Shows fall in temperature.
Examples: reaction between citric acid + sodium hydrogencarbonate; thermal decomposition
3
Q
What does an exothermic reaction profile look like?
A
- Lots of reactants so graph starts high up
- Activation energy goes from reactants to turning point of curve (small Activation energy)
- Energy released is difference from reactants to products
- Little products so graph ends low down
4
Q
What does an endothermic reaction profile look like?
A
- Little reactants so graph starts down low
- Activation energy is from reactants to turning point of curve (high Activation energy)
- Energy absorbed is difference from reactants to products
- Lots of products so graph ends high up
5
Q
What kind of reaction is bond breaking and why?
A
It is an endothermic reaction because energy is supplied to break existing bonds
6
Q
What kind of reaction is bond formation and why?
A
It is an exothermic reaction because energy is released when new bonds are formed
