Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry Year 10 (GCSE) AQA > C5- Energy Changes > Flashcards

C5- Energy Changes Flashcards

You may prefer our related Brainscape-certified flashcards:
GCSE Geography - AQA flashcards AP® Chemistry flashcards GCSE Religious Studies - Edexcel Route B flashcards GCSE Religious Studies - Eduqas Route A flashcards GCSE Religious Studies - Edexcel Route A flashcards GCSE Religious Studies - Eduqas Route B flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

What is an exothermic reaction?

A

A reaction where energy is transferred to the surroundings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Give examples of exothermic reactions.

A

1) Combustion
2) Respiration
3) Neutralisation reactions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens to the temperature of the surroundings during an exothermic reaction?

A

The temperature of the surroundings increases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is an endothermic reaction?

A

A reaction where energy is transferred from the surroundings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Give examples of endothermic reactions.

A

1) Thermal decomposition reactions.
2) The reaction between citric acid and sodium hydrogen carbonate.
3) Certain respiration.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens to the temperature of the surroundings during an endothermic reactions?

A

The temperature of the surroundings decrease.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

State two uses of exothermic reactions.

A

1) Self-heating cans.

2) Hand warmers.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

State a use of endothermic reactions.

A

Some cooling sports injury packs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are reactants?

A

The substances involved in a chemical reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are products?

A

The substances formed when reactants have a chemical reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a reaction profile?

A

A diagram which shows whether the reactants have more or less energy than the products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why does the reaction profile always go up at the start?

A

A reaction starts with bonds being broken.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the activation energy.?

A

The energy needed to break bonds to start a reaction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why does the reaction profile always go down at the end?

A

A reaction always ends with bonds being made.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

If the reactants have more energy than the products, what kind of a reaction must have taken place?

A

An exothermic one. Energy has been transferred to the surroundings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

If the reactants have less energy than the products, what kind of a reaction must have taken place?

A

An endothermic one. Energy has been taken in from the surroundings.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Is breaking bonds endothermic or exothermic?

A

Endothermic. Chemical bonds are strong so require energy to break (like when you have to put energy in to separate magnets from each other).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Is making bonda endothermic or exothermic?

A

Exothermic. Energy is released when chemical bonds are formed (like how two magnets move together when close and generate kinetic energy).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do we work out the overall energy change of a reaction?

A

Work out the difference between the energy needed to break all the bonds in the reactants and the energy released to form all the bonds in the products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do we work out the energy change from a reaction profile?

A

The difference between the energy of the reactants and the energy of the products.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How do we work out the activation energy from a reaction profile?

A

The difference between the energy of the reactants and the highest point on the profile.

22
Q

What is a chemical cell?

A

A unit which contains chemicals which produce electricity through a reaction.

23
Q

What are the main components of a chemical cell?

A

An anode, a cathode (made of 2 different metals and an electrolyte.

24
Q

What is an electrolyte?

A

A solution containing ions.

25
Q

What does the voltage of a cell depend on?

A

The type of electrode and the electrolyte.

26
Q

What is a battery?

A

Two or more cells connected in series.

27
Q

What happens to the electrodes in a chemical cell?

A

The more reactive metal is used up and the less reactive on increases in size.

28
Q

In non-rechargeable cells, why do the chemical reactions stop over time?

A

One of the reactants become used up.

29
Q

How can certain cells be recharged?

A

Applying an external electric current.

30
Q

How does the reactivity of the metal electrodes affect the size of the potential difference?

A

Which way do electrons move in a cell?

31
Q

What is a fuel cell?

A

A cell which uses a fuel and oxygen (or air) to generate electricity.

32
Q

What are the products in a hydrogen fuel cell?

A

Water.

33
Q

State 2 advantage of hydrogen fuel cells.

A

1) Do not need to be recharged.

2) No pollutants are produced.

34
Q

State three disadvantages of hydrogen fuel cells.

A

1) Hydrogen is highly flammable.
2) Hydrogen is often made from fossil fuels.
3) Hydrogen is difficult to store.

35
Q

What reaction occurs at the positive electrode of a hydrogen fuel cell?

A

O2 + 4Hᐩ + 4e⁻ -> 2H₂O

36
Q

Which reaction occurs at the negative electrode of a hydrogen fuel cell?

A

H₂ -> 2H + 2e⁻

37
Q

Give 2 examples of fuels.

A

1) Natural gas

2) Methane

38
Q

How do sports injury packs work?

A

When squeezed forcefully, ammonium nitrate and water mix in the pack, resulting in instant cooling.

39
Q

Give the 2 requirements for a successful reaction to take place.

A

1) Collision= Particles of the reactants have to collide.
2) Activation energy= The collisions that happen between particles of the reactants must take place with enough energy. This threshold amount of energy is called the activation energy.

40
Q

How do catalysts work in reactions?

A

They increase the rates of reactions by decreasing the activation energy, which increases the chance of successful collisions.

41
Q

How can we figure out whether a reaction is endothermic or exothermic?

A

By subtracting the total bond energies of the products from the total bond energies of reactants, we can see if a reaction is endothermic or exothermic.

42
Q

Give the rule for the energies of bonds in exothermic reactions.

A

Energy released by making bonds > energy required to break bonds.
I.e. overall energy change of reaction < 0

Endothermic reactions

43
Q

Give the rule for the energies of bonds for endothermic reactions.

A

Energy released by making bonds < energy required to break bonds.
I.e. overall energy change of reaction > 0

44
Q

Define a battery

A

A battery is a collection of more than one cell joined in series (end-to-end).

45
Q

How do you calculate the voltage of a battery?

A

It is the sum of the voltages of the individual cell components.

46
Q

Give 4 advantages to fuel cells.

A

1) Reliable
2) Less pollution than traditional methods
3) High efficiency
4) Compact and lightweight.

47
Q

How do fuel cells produce electricity?

A

Fuel cells produce electrical energy efficiently by using energy produced by a particular reaction.

48
Q

What is the reaction used in fuel cells to produce electrical energy?

A

The reaction is between an external fuel source and oxygen. Once added to the cell, the fuel is oxidised, this causes a voltage to be established.

49
Q

What is the only waste product of a hydrogen fuel cell?

A

Water

50
Q

What is the half equation for the negative electrode in a hydrogen fuel cell?

A

2H₂ -> 4H⁺ + 4e⁻

51
Q

What is the half equation for the positive electrode of a hydrogen fuel cell and what happens here?

A

O₂ + 4H⁺ + 4e⁻ -> 2H₂O

Oxygen combines with the hydrogen to form this product. (Water) The hydrogen is being oxidised.

52
Q

What is the overall equation for a hydrogen fuel cell?

A

2H₂ + O₂ -> 2H₂O

Chemistry Year 10 (GCSE) AQA (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions