C3.3.1 Energy from reactions Flashcards
What is calirometry?
Measuring the amount of energy transferred during a reaction.
Give a basic example of a calirometry experiment.
Heating water in a glass or metal container and measuring the temperature change.
What equation do you use to measure the amount of energy released by a fuel?
Q = mc ΔT
Q = energy transferred m = mass c = specific heat capacity ΔT = change in temperature
What happens to the bonds in a chemical reaction?
The bonds in the reactants are broken.
New bonds are created in the products.
Breaking bonds _______ energy.
Breaking bonds REQUIRES energy.
Making bonds _______ energy.
Making bonds RELEASES energy.
Describe an exothermic reaction.
Exothermic reactions give out heat energy to the surroundings.
Negative energy change - products have less energy than reactants.
Give 2 examples of exothermic reactions.
Combustion
Neutralisation reactions (acids + alkali)
Describe an endothermic reaction.
Endothermic reactions absorb heat energy from the surroundings.
Positive energy change - products have more energy than reactants.
Give 2 examples of endothermic reactions.
Electrolysis
Reaction between ethanoic acid and sodium carbonate
What is activation energy?
Energy that is supplied to the reactants to start a reaction.
What is a catalyst?
A substance that speeds up the rate of a chemical reaction without being used up in the reaction.
How does a catalyst work?
They provide a different pathway for the reaction to follow with a lower activation energy than the one followed by the uncatalysed reaction.
As a result, a greater proportion of reacting particles have enough energy to react.
How can hydrogen be used as a fuel in cars?
Burning hydrogen directly in the engine
Hydrogen fuel cells where the hydrogen reacts with oxygen without burning.
Give 2 benefits of using hydrogen to power cars.
Hydrogen does not generate carbon dioxide when burnt
Hydrogen fuel cells are very efficient
