C3.2 - Energetics Flashcards
What is an exothermic reaction?
A reaction where energy is transferred to the surroundings.
This results in the temperature of the surroundings increasing
What are some examples of an exothermic reaction?
Combustion (e,g burning a fuel to cook)
Neutralisation ( sodium hydroxide reacting with dilute hydrochloric acid).
Oxidation reactions
What is an endothermic reaction?
One where energy is taken in from the surroundings
The temperature of the surroundings decreases
What is an example of an endothermic reaction?
The reaction between citric acid and sodium hydrogen carbonate in sherbet sweets
Photosynthesis in plants which involves carbon dioxide and water reacting to form sugars by using energy in light
Thermal decomposition reactions.
Ice packs
How can you find out if a reaction involving a solution is exothermic or endothermic?
- Measure the start temperature of a solution in an insulated container
- Add the other reactant and stir
- Measure the end temperature of the mixture
- Calculate the difference between the start and end temperature
Is bonds breaking endothermic or exothermic?
Endothermic
Is bonds forming endothermic of exothermic ?
Exothermic
What is a reaction profile?
It is a chart that shows the energy involved in a reaction
What is activation energy?
Energy must be transferred to the reactant particles to start most chemical reactions
Activation energy is the minimum energy needed for a reaction to start
It is often provided by heating and it breaks bonds in the reactants .
What are bond energies?
Energy must be transferred to molecules to break their bonds.
The energy needed to break 1 mol of a particular bond is the bond energy.
How do you calculate the energy change ?
Energy change = (energy transferred to break bonds) -
➖ (energy transferred when bonds are made )
