C3.3.1 Energy from reactions Flashcards

1
Q

What is calirometry?

A

Measuring the amount of energy transferred during a reaction.

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2
Q

Give a basic example of a calirometry experiment.

A

Heating water in a glass or metal container and measuring the temperature change.

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3
Q

What equation do you use to measure the amount of energy released by a fuel?

A

Q = mc ΔT

Q = energy transferred
m = mass
c = specific heat capacity
ΔT = change in temperature
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4
Q

What happens to the bonds in a chemical reaction?

A

The bonds in the reactants are broken.

New bonds are created in the products.

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5
Q

Breaking bonds _______ energy.

A

Breaking bonds REQUIRES energy.

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6
Q

Making bonds _______ energy.

A

Making bonds RELEASES energy.

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7
Q

Describe an exothermic reaction.

A

Exothermic reactions give out heat energy to the surroundings.

Negative energy change - products have less energy than reactants.

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8
Q

Give 2 examples of exothermic reactions.

A

Combustion

Neutralisation reactions (acids + alkali)

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9
Q

Describe an endothermic reaction.

A

Endothermic reactions absorb heat energy from the surroundings.

Positive energy change - products have more energy than reactants.

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10
Q

Give 2 examples of endothermic reactions.

A

Electrolysis

Reaction between ethanoic acid and sodium carbonate

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11
Q

What is activation energy?

A

Energy that is supplied to the reactants to start a reaction.

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12
Q

What is a catalyst?

A

A substance that speeds up the rate of a chemical reaction without being used up in the reaction.

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13
Q

How does a catalyst work?

A

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.

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14
Q

How can hydrogen be used as a fuel in cars?

A

Burning hydrogen directly in the engine

Hydrogen fuel cells where the hydrogen reacts with oxygen without burning.

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15
Q

Give 2 benefits of using hydrogen to power cars.

A

Hydrogen does not generate carbon dioxide when burnt

Hydrogen fuel cells are very efficient

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16
Q

Give 3 disadvantages of using hydrogen.

A

Hydrogen is not highly available from petrol stations

Hydrogen is difficult to store safely

The production of hydrogen uses fossil fuels

17
Q

How do you calculate bond energies?

A

Add together all the bond energies for all the bonds in the reactants.

Add together the bond energies for all the bonds in the products.

Calculate the energy change.