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GCSE AQA COMBINED SCIENCE BASEBALL > Chemistry C5 Energy Changes > Flashcards

Chemistry C5 Energy Changes Flashcards

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1
Q

What happens in chemical reactions?

A

Energy changes

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2
Q

What does energy change mean?

A

It means that energy moves around

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3
Q

What can chemicals store?

A

Energy

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4
Q

Do all chemicals store the same amount of energy?

A

No

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5
Q

What are the two things produced in a reaction?

A

The reactant(s) going in and the product(s) as the result

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6
Q

What happens if the products of a reaction store more energy than the original reactants?

A

They have taken in energy from the surroundings

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7
Q

What happens if they store less?

A

It has been transferred to the surroundings

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8
Q

Does the overall energy of the reaction go up or down?

A

It stays the same - this is why the amount of energy in the universe is constant and never increases or decreases

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9
Q

What is reaction that gives out energy?

A

Exothermic

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10
Q

How is exothermic energy normally given out?

A

By heat

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11
Q

Give a common example

A

Burning fuels

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12
Q

What is the burning of fuels also known as?

A

Combustion

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13
Q

What is a nuetralisation reaction?

A

Its a reaction involving an acid and alkali

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14
Q

Are neutralisation reactions exothermic?

A

Yes

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15
Q

What is an oxidation reaction?

A

A reaction that gains Oxygen

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16
Q

Is oxidation exothermic?

A

Sometimes

17
Q

Give an example of an exothermic oxidation reaction?

A

Adding sodium to water - sodium moves around the surface of the water as it is oxidised

18
Q

Give some examples of exothermic reactions

A

Hand warmers and some tinned drinks

19
Q

What is a reaction that takes heat in?

A

Endothermic

20
Q

Which are more common Exo- or Endo- thermic reactions?

A

Endothermic reactions are less common

21
Q

Give an example of an endothermic reaction?

A

Citric acid and sodium hydrogencarbonate

22
Q

Give another example of endothermic reaction?

A

Calcium carbonate + heat -> co2 + CaO (quicklime)

23
Q

Can you give some everyday endothermic reactions?

A

Athletic heating packs

24
Q

Can energy transfer be measured in thermic reactions?

A

Yes

25
Q

Describe how you would carry out a practical to measure the reaction?

A

Measure the temperature of the reactants and mix them in a polystyrene cup

26
Q

What is the biggest problem in these exercises?

A

That energy is lost to the environment

27
Q

What can you do to save heat

A

Pad the cup with wool and put a lid on the cup

28
Q

What kinds of reactions that this approach work well for?

A

Neutralisation reactions

29
Q

What other things can you control for?

A

Concentration and mass

30
Q

What is a reaction profile?

A

It shows the chemical potential energy as the reactants proceed to products

31
Q

What do you see in an exothermic reaction?

A

You see the end point lower than the starting point

32
Q

What does the height difference represent?

A

The energy change - its a direct measure of the loss

33
Q

What do you see in an endothermic reaction?

A

You see the endpoint higher

34
Q

What is the difference between the starting point and the top of the curve?

A

This is known as the activation energy.

35
Q

What does the activation energy represent?

A

It represents the minimum energy that the reactants need to collide and start the reaction

36
Q

Why do you need to supply this activation energy?

A

To break the bonds between molecules.

37
Q

What happens during a reaction in terms of bonds?

A

Old ones are broken and new ones formed.

38
Q

What direction does energy flow when breaking bonds?

A

It must be supplied - hence it is endothermic

39
Q

What direction does energy flow when forming bonds?

A

it is released hence it is exothermic

GCSE AQA COMBINED SCIENCE BASEBALL (1 decks)

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