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Energy Changes - Coggle Diagram
Energy Changes
Reaction Profiles
Relative energies of reactants and products in reaction
How energy changes over course of reaction
Exothermic Reactions
products
lower
energy than reactants
difference in height
energy given out
Endothermic Reactions
products
higher
energy than reactants
difference in height
energy taken in
Activation Energy
minimum energy needed by particles when they collide for a reaction to occur
greater activation energy
more energy needed to start reaction
energy difference between reactants and peak of graph
Bond Energies
During chemical reaction
Energy
supplied
to
break
bonds in reactants
Energy
released
when products are
formed
Overall energy change = sum of energy required to break bonds - sum of energy released to form bonds
Endothermic
Energy taken in > energy released
Exothermic
Energy taken in < energy released
Exothermic and Endothermic
Exothermic
Temperature rise
Examples
Combustion
Neutralisation
Oxidation
Everyday uses
hand warmers
self heating cans
Negative ΔH
Energy is transferred to the surroundings
Endothermic
Energy taken in from surroundings
Temperature fall
Examples
Thermal decomposition
Everyday uses
Sports injury packs
Positive ΔH
Practical
Cells and batteries
Cell
Electrochemical Cell
Two different electrodes
conduct electricity
metal
Electrolyte
liquid containing ions to react with electrodes
Connect electrodes by wire allows charge to flow
Electricity
Voltage
voltmeter
Voltage Factors
Type of electrode
different metals react differently with same electrolyte
Bigger difference in reactivity of electrodes
bigger voltage
Electrolyte
different ions react differently with electrodes
Battery
2 or more cells connected together in a series
Higher voltage
Non-rechargeable
Alkaline batteries
Reactions stop when one reactant is used up
Irreversible reactions
Rechargeable
Reactions reversed by connecting it to external electric current