Chemistry Topic 5 Energy Changes - Coggle Diagram
Chemistry Topic 5 Energy Changes
Products are at a lower energy level than reactants. When the reactants form products they transfer some energy to the surroundings. The temperature of the surroundings increases.
Reactants are at a lower energy level than products. When the reactants form products energy is transferred from the surroundings. The temperature of the surroundings decreases.
Chemical reactions only happen when atoms collide with sufficient energy. The minimum amount of energy required to begin a reaction is called the
Hydrogen fuel cells
Symbol Equation: H2 + O2 ------- H20
Word Equation: Hydrogen + Oxygen ------ Water
Advantages: NO pollutants produced, can be a range of sizes.
Disadvantages: Hydrogen is highly flammable, hydrogen is hard to store.
Types of Reactions
Endothermic: Energy is taken from the surroundings. E.g. Sports packs, thermal decomposition
Exothermic: Energy is transferred to the surroundings. E.g. Combustion, hand warmers, neutralisation
Cells and Batteries
by adding two different metals together in contact with electrolyte.
are two or more cells connected together to make a greater voltage.
Alkaline batteries. Stop working when one of the reactants is all used up.
Can be recharged because the chemical reactions are reversed when an external electrical current is applied.
Bond energy calculations
Calculate the energy for the bond making and the bond breaking
Then the overall energy change is the reactants minus the products.
If its a negative number its an exothermic reaction. Or if its positive then its an endothermic reaction.