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C5

QuestionAnswer
What is the law for conservation of energy Energy cannot be created or destroyed only transferred
Describe an exothermic reaction Transfers energy to its surroundings
Describe endothermic reactions Takes energy in from surroundings
Give 2 examples of exothermic reactions Respiration and combustion
Give 2 examples of endothermic reactions Photosynthesis and electrolysis
What is activation energy The energy required for a reaction to take place
What must happen for particles to react They must collide and the activation energy must be reached
How would you calculate bond energies 1. Balance formula 2. Draw diagrams 3. Write energy for each bond 4. Multiply energy for each bond 5. Total energies for breaking and making 6. Bonds made - bonds broken
How do you make a simple cell Connect 2 different metals in contact with an electrode
What do cells contain Chemicals which react to produce electricity
What factors affect the voltage produced by a cell Type of electrode and electrolyte
What is the difference between rechargeable and non rechargeable cells The reaction in a rechargeable cell can be reversed by inputting energy
Alkaline batteries are... Non rechargeable
Why do non rechargeable cells and batteries stop working The reaction is non reversable
How is a rechargeable cell recharged Reversing the reaction
What is a battery Two or more cells connected in series
Describe how a fuel cell works in terms of oxidation Hydrogen is oxidised and the negative electrons produce current
Write a half equation for the reaction at the positive electrode inva hydrogen fuel cell 4H+ + 4e- +2O2 -> H2O
Write a half equation for the reaction at the negative electrode in a hydrogen fuel cell H2 - 2e- -> 2H+
What are the advantages of hydrogen fuel cells -less pollutants -cheaper -batteries can only be recharged a certain number of times -batteries store less energy
What are the disadvantages of hydrogen fuel cells -gas takes up more space -explosive so hard to store -often made from hydrocarbons so pollution
What is an anomaly
Created by: Liam P