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Chemistry Paper 1 > Unit 7 Energy Changes > Flashcards

Unit 7 Energy Changes Flashcards

(64 cards)

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1
Q

What’s an exothermic reaction

A

A reaction that transfers energy from reacting molecules to the surrounding

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2
Q

Name a common example of an exothermic reaction

A

Wood burning

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3
Q

What’s an endothermic reaction

A

A reaction that takes in energy from the surroundings

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4
Q

What happens to the surroundings during an exothermic reaction

A

The temperature of the surroundings increases

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5
Q

What is combustion

A

Burning

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6
Q

Is oxidation an endo or exothermic reaction

A

Exothermic

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7
Q

Is neutralisation an endo or exothermic reaction

A

Exothermic

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8
Q

What is and energy profile

A

A graph with the time of reaction on the x axis and energy changes on the y axis

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9
Q

On the energy profile for exothermic reactions is the energy of the reactants higher that the products

A

The energy of the reactants is above the energy of the products

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10
Q

What does the difference in the levels of energy of the reactants and products in a energy profile show

A

The total energy released to the surroundings

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11
Q

On the energy profile of an **endothermic reaction ** is the energy of the reactants higher than the energy of the products

A

No
The energy of the products is higher than the energy of the reactants

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12
Q

Name the two uses for exothermic reactions

A

Hand warmers
Self heating objects

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13
Q

What is a common example of an endothermic reaction

A

Thermal decomposition

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14
Q

Is thermal decomposition endo or exothermic

A

Endothermic

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15
Q

What happens to the surroundings during a endothermic reaction

A

The temperature of the surroundings decreases

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16
Q

What is the activation energy

A

The minimum amount of energy need for the reaction to occur

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17
Q

Why is there an activation energy

A

Because there is a minimum amount of energy to make the particles collide

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18
Q

How do you identify the activation energy on an energy profile

A

From the reactants to the peak of the curve

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19
Q

Which requires more energy to occur endo or exothermic reactions

A

Endothermic reactions

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20
Q

Are energy changes for exothermic reactions + or -

A

Negative

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21
Q

Why are exothermic reactions energy changes negative

A

Because energy is being transferred (lost) to the surroundings

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22
Q

Are endothermic reactions energy changes + or -

A

Positive

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23
Q

Why are endothermic reactions energy changes positive

A

Because energy is gained from the surroundings

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24
Q

Is the breaking of bond’s endo or exothermic

A

Endothermic

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25
Why are breaking bonds endothermic
Because it requires energy to break the bond
26
Is making bonds endothermic or exothermic
Exothermic
27
Why is making bond exothermic
Because we release energy when making bonds
28
Every chemical bond has a what
Energy value
29
What does the energy value tell us
The energy required to break that bond
30
H2 + Cl2 ———> 2HCl Which bond are broken and which are being made
The H an Cl are breaking The 2HCl is being made
31
What is the formula for total energy value
Total of bond breaking ———————-———— Total of bong making
32
What type of reaction is the required practical temperature changes
Neutralisation
33
What are the steps to the temperature changes practical
-Add increasing volumes of alkali into the acid -Record the maximum temperature reached
34
What is the independent variable in the temperature changer RP
The volume of alkaline
35
What is the dependant variable in the temperature change RP
The maximum temperature reached
36
What is the control variables in the temperature change RP
The volume of acid and concentration of both the acid and alkaline
37
Sate the equipment used in the temperature change Rp in order of use
Measuring cylinder Polystyrene cup Beaker Thermometer Plastic lid
38
Why do we use a polystyrene cup with a lid in the temperature change RP
To avoid heat escaping to the surroundings and its a good insulator
39
Why Do we place the polystyrene cup in the beaker
To avoid the polystyrene cup from falling over
40
What are the acid and alkaline solution used in the temperature change RP
Acid - HCl Alkaline- NaOH
41
On the graph of the results on the experiment (temperature change RP) we can see the more Alkaline added the temperature increases Why
Because when we add more NaOH there are more particles to react with the HCl
42
On a certain point on the temperature change RP graph the temperature starts to go back down why
Because there is too much NaOH that HCl becomes the limiting reactants do some particles of NaOH don’t react
43
Explain in terms of energy why at a certain point on the graph of temperature changes RP the temperature decreases
Because the energy released is being spread over a greater volume so each net temperature is lower
44
What’s an electrolyte
A solution that ions can move through
45
Describe the strict of a chemical cell
two metals in an electrolyte which produces electricity
46
Why do cells eventually stop working
Because the chemicals in the cell run out and the reactions stop happening
47
How do cells create electricity
The metals and the electrolyte react producing an electrical current
48
Why does two metals with the biggest difference in reactivity produce the most electricity
Because these two metals create the largest potential difference
49
Why is the best metals to use in a cell magnesium and copper
Because these two metals have the largest difference in reactivity
50
What other factor others than the two metals used affect the amount of volts produced
The electrolyte
51
What is a battery is it better than a cell
A battery is an object that contains two or more cells connected in series to produce a greater voltage than cells
52
Name an example of non rechargeable battery and why is it considered non rechargeable
Alkaline batteries Because you can’t reverse the reactions
53
Name an example of a rechargeable battery and why are they rechargeable
Lithium battery’s Because we can reverse chemical reactions when an electrical current is applied
54
State the names and charges of the electrodes in the **Fuel cell**
Anode - negative Cathode - positive
55
How does a fuel cell work 1st step
-Hydrogen comes in from one side and reacts with the negative anode to form H plus and negative electrons
56
What does the wire that’s connected to the two electrodes do
It allows electrons to move from the side to the cathode
57
How do fuel cells work 2nd step
The electrons move through the wire to the cathode whilst the hydrogen moves through the electrolyte to the cathode
58
How to fuel cells work 3rd step
Oxygen comes in from the other side and react with the H+ and the - electrons to form water
59
Why do we need two hydrogen molecules in a fuel cell
Because there will be an oxygen still left to react
60
State the half equation for Hydrogen in the fuel cell
H2 ———> 2H+ + 2e-
61
State the half equation for the water produced in a fuel cell
O2 + 4H+ + 4e- ————> 2H2O
62
State the overall equation in the fuel cell
O2 + 2H2 ———> 2H20
63
State the advantages of using Hydrogen fuel cells
- They only require H and O - They don’t produce CO2 - Simple and last longer
64
State the disadvantages of Hydrogen fuel cells
- Hydrogen gas is hard to store - Requires energy to use anyway

Chemistry Paper 1 (2 decks)

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