C7: Energy Changes
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What are the two types of chemical reaction
Exothermic Endothermic
What is an exothermic reaction
A reaction that releases energy
What is the effect of an exothermic reaction
Temperature increased Energy from reacting chemicals is transferred to the surroundings Heat things up
What are examples of exothermic reactions
Combustion Neutralisation Oxidation Hand warmers
What is an endothermic reaction
A reaction that absorbs energy
What is the effect of an endothermic reaction
Temperature of surroundings is decreased Energy from surroundings is transferred to the reacting chemicals Cooling things down
What are examples of endothermic reactions
Any decomposition type The reaction between citric acid and baking soda (sodium bicarbonate) Sports injury packs
What type of reaction is a self heating can
Exothermic
What are the two variables required for a reaction to take place
Collisions Activation energy
What are collisions
Movement of particles in a reaction
What is activation energy
Amount of energy given to the reactants to start the reaction
What is a reaction profile
Reaction profiles show the progress of reaction on the x axis and the energy level on the y axis. Reaction profiles will tell us Activation energy of a reaction Overall energy change happening as a result of the reaction Amount of energy contained within the products and the reactants
What is a catalyst
An enzyme that speeds up the reaction without being used up itself.
What would we have to do if we add a catalyst
Decrease the activation energy to increase the rate of reaction
What is a bond energy
Energy that measures the strength of chemical bonds.
How do we use bond energies to find out if the reaction is exothermic or endothermic
Total bond energies of products - Total bond energies or reactants
What does making bonds require
Releasing energy Bond making = exothermic reaction
How do we know if it is an exothermic reaction
Amount of bonds made is more than the amount of bonds broken The overall energy change is a negative value, meaning it is less than 0
What does bond breaking require
Energy. Bond breaking = exothermic reaction
How do we know if it is an endothermic reaction
Amount of bonds made is less than the amount of bonds broken The overall energy change is a positive value, meaning it is more than 0