Topic C5 - Energy Changes Flashcards
How is energy moved around?
Energy is moved around in chemical reactions
What happens in an exothermic reaction ?
In an exothermic reaction energy is given out
How is am exothermic reaction shown?
An exothermic reaction is shown by a rise im temperature of the surroundings
What are some examples of exothermic reactions?
Examples of exothermic reactions include:
- burning fuels - also called combustion
- neutralisation reactions (acid + alkali)
- many oxidation reactions
What are some exothermic reactions that are used for everyday uses?
- some hand-warmers use an exothermic reaction to release energy
- self heating cans of hot chocolate and coffee also use exothermic reactions between chemicals in their bases
What happens in an endothermic reaction?
In an endothermic reaction energy is taken in
How is an endothermic reaction shown?
An endothermic reaction is shown by a fall im temperature of the surroundings
Examples of endothermic reactions
- reaction between citric acid and sodium hydrogen-carbonate
- thermal decomposition (when a substance breaks down when its heated)
Everyday uses of endothermic reactions include
- used in some sport injury packs. The chemical reaction allows the pack to become instantly cooler without having to put it in the freezer
What does exo mean?
Exo means exit
What are reaction profiles?
Reaction profiles are handy little diagrams which show you the changes in energy during a reaction
What is the activation energy?
Activation energy is the minimum amount of energy the reactants need to react when they collide with each other
Why is activation energy needed?
Activation energy is needed to start a reaction
What happens the greater the activation energy is?
The greater the activation energy, the more energy is needed to start the reaction. This energy has to be given e.g. by heating the reaction mixture
What do reaction profiles show?
Reaction profiles show energy changes
