C7

Question 1

what is an exothermic reaction

Answer 1

a reaction in which energy is transferred to the surrounding

Question 2

what is an endothermic reaction

Answer 2

where energy is transferred from the surrounding to the reactants

Question 3

describe what an exothermic reaction profile looks like

Answer 3

https://www.google.com/search?q=reaction+profiles&tbm=isch&ved=2ahUKEwiEk8aGw5f6AhUNfBoKHSOsDW4Q2-cCegQIABAA&oq=reaction+profiles&gs_lcp=CgNpbWcQDFAAWABgAGgAcAB4AIABAIgBAJIBAJgBAKoBC2d3cy13aXotaW1n&sclient=img&ei=3nsjY4SsBY34aaPYtvAG&bih=625&biw=1366#imgrc=aA5EF-fT06sZYM

Question 4

what does an endothermic reaction profile look like

Answer 4

https://www.google.com/search?q=reaction+profiles&tbm=isch&ved=2ahUKEwiEk8aGw5f6AhUNfBoKHSOsDW4Q2-cCegQIABAA&oq=reaction+profiles&gs_lcp=CgNpbWcQDFAAWABgAGgAcAB4AIABAIgBAJIBAJgBAKoBC2d3cy13aXotaW1n&sclient=img&ei=3nsjY4SsBY34aaPYtvAG&bih=625&biw=1366#imgrc=DuYrPoCHA3SnKM

Question 5

what is the activation energy

Answer 5

the minimum amount of energy needed for a reaction to occur

Question 6

what is a catalyst

Answer 6

any chemical which speeds up a reaction (is it lowers the activation energy) without getting used up

Question 7

what does a catalyst do

Answer 7

provides an alternate route for the reaction to take place with a lower activation energy

Question 8

what type of reaction is bond breaking

Answer 8

endothermic as energy is taken in from the surroundings to break the bonds

Question 9

what type of reaction is bond making

Answer 9

an exothermic reaction as energy is released when bonds are made

Question 10

what type of reaction is bond making

Answer 10

an exothermic reaction as energy is released when bonds are made

Question 11

do Q1 c and if you can you’ll be fine

Answer 11

https://files.cognitoedu.org/files/3%20-%20GCSE/2%20-%20Qs%20by%20Topic/2%20-%20Chemistry/1%20-%20AQA%20[EB]/Exothermic%20_%20Endothermic%20Reactions%203%20QP.pdf

Question 12

what are the steps for the energy changes practical

Answer 12

1. Use a measuring cylinder to put 30 cm3 dilute hydrochloric acid into the polystyrene cup. Stand the cup inside the beaker. This will make it more stable.
2. Use the thermometer to measure the temperature of the acid. Record it on a piece of paper
3. Put 5 cm3 sodium hydroxide solution into the 10 cm3 measuring cylinder.
4. Pour the sodium hydroxide into the cup. Fit the lid and gently stir the solution with the thermometer through the hole.
5. When the reading on the thermometer stops changing, record the temperature.
6. Pour out the solution and rinse the polystyrene cup with water a few times.
7. Repeat steps 1 to 6 to except add a further 5 cm3 amounts of sodium hydroxide to the cup. Till you reach a total of 40 cm3 needs to be added.

Question 13

what does the graph look like for the energy changes practical

Answer 13

a line going up and then falling. make sure there’s a curve and for the line of best fit; draw 2 lines one going from the end going straight and the second one from the start going straight up. where the 2 lines intersect; going down that’s how much sodium hydroxide was needed to neutralize 30cm3 of HCL acid.

Question 14

what are the different types of batteries

Answer 14

dry cell
batteries
rechargeable batteries
fuel cells
hydrogen powered cells

Question 15

what are dry cells

Answer 15

they are a type of non-rechargeable batteries as once the chemical reactants are used up they cant be reverted so the electric output gradually falls.

Question 16

what are some factors affecting the voltage produced by the cell

Answer 16

the type of electrode and electrolyte. the higher the difference in reactivity between the 2 metals, the higher the voltage produced

Question 17

how can you make a cell

Answer 17

by dipping 2 metals (connected with a wire) into an electrolyte which will cause electrons to flow from the more reactive metal to the less reactive metal

Question 18

what is a battery

Answer 18

a battery contains 2 or more cells connected in series

Question 19

what is a rechargeable battery

Answer 19

a battery in which electricity can be used to remake the chemical reactants as the chemical reaction in which a battery produces electricity is reversible.

Question 20

what is a rechargeable battery

Answer 20

a battery in which electricity can be used to remake the chemical reactants as the chemical reaction in which a battery produces electricity is reversible.

Question 21

what are fuel cells

Answer 21

a special battery in which fuel is used to produce the electrical current. the fuel just needs refuelling, it doesn’t need to be recharged or replacing. the fuel can wary from methanol to hydrogen

Question 22

what are hydrogen powered vehicles

Answer 22

vehicles who use hydrogen as fuel instead of the normal oil

Question 23

explain how hydrogen fuel cell works

Answer 23

hydrogen gas is supplied to the negatively charged electrodes . it diffuses through the graphite and reacts with hydroxide ions to make water and produce electricity. Oxygen gas is supplied to the positively charged electrode. It diffuses through the graphite and reacts to form hydroxide ions, which then react with hydrogen to make water. the water then leaves the cell.

Question 24

what are the advantages and disadvantages of hydrogen fuel cells.

Answer 24

Advantages of hydrogen fuel cells:
Do not need to be electrically recharged
No pollutants are produced
Can be a range of sizes for different uses

Disadvantages of hydrogen fuel cells:
Hydrogen is highly flammable
Hydrogen is sometimes produced for the cell by non-renewable sources
Hydrogen is difficult to store

Question 25

what is the half equation for hydrogen reacting with hydroxide ions

Answer 25

2H2(g) + 4OH-(aq) —> 4H20(l) + 4e-