P1- Energy changes Flashcards
What happens when chemical reactions occur?
Energy is transferred from the chemicals to or from the surroundings. Therefore, many reactions are accompanied by a temperature change
Exothermic reactions
Accompanied by a temperature rise. Transfers heat energy from the chemicals to the surroundings (give out heat energy)
Endothermic reactions
Accompanied by a fall in temperature. Heat energy is transferred from the surroundings to the chemicals (take in heat energy)
Method for investigating the variables that affect temperature changes in reacting solutions
Set up equipment shown, take temperature of the acid, add the metal powder and stir, record highest temp the reaction mixture reaches, calculate the temp change for the reaction and repeat the experiment using a different metal
Energy level diagrams
In chemical reactions, atoms are rearranged as old bonds are broken and new bonds are formed. For bonds to be broken, reacting particles must collide with sufficient energy.
Activation energy
The minimum amount of energy the particles need for a reaction to take place
How can the energy changes in a chemical reaction be shown
Energy level diagram or reaction profile
What happens in an exothermic reaction
Energy is given out to the surroundings and the products have less energy than the reactants. Temp of surroundings increases. Includes combustion, oxidation reactions and neutralisation
What happens in an endothermic reaction
Energy is being taken in from the surroundings and the reactants have less energy than the products. Temp of surroundings decreases. Includes thermal decomposition of metal carbonates
What do catalysts do
Reduce the activation energy needed for a reaction. This makes the reaction go faster
In a chemical reaction what new substances are produced
The bonds in the reactants are broken, new bonds are made to form the products
What does breaking a bond require
Energy, it is an endothermic process
If more energy is required to break the bonds than is released when bonds are formed, what reaction is it
Endothermic
If more energy is released when bonds are formed than is required to break the bonds what reaction is it
Exothermic
Equation for energy change
Bonds broken- bonds made
