C7 Flashcards
what is an exothermic reaction
a reaction in which energy is transferred to the surrounding
what is an endothermic reaction
where energy is transferred from the surrounding to the reactants
describe what an exothermic reaction profile looks like
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
what does an endothermic reaction profile look like
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
what is the activation energy
the minimum amount of energy needed for a reaction to occur
what is a catalyst
any chemical which speeds up a reaction (is it lowers the activation energy) without getting used up
what does a catalyst do
provides an alternate route for the reaction to take place with a lower activation energy
what type of reaction is bond breaking
endothermic as energy is taken in from the surroundings to break the bonds
what type of reaction is bond making
an exothermic reaction as energy is released when bonds are made
what type of reaction is bond making
an exothermic reaction as energy is released when bonds are made
do Q1 c and if you can you’ll be fine
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
what are the steps for the energy changes practical
- 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.
- Use the thermometer to measure the temperature of the acid. Record it on a piece of paper
- Put 5 cm3 sodium hydroxide solution into the 10 cm3 measuring cylinder.
- Pour the sodium hydroxide into the cup. Fit the lid and gently stir the solution with the thermometer through the hole.
- When the reading on the thermometer stops changing, record the temperature.
- Pour out the solution and rinse the polystyrene cup with water a few times.
- 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.
what does the graph look like for the energy changes practical
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.
what are the different types of batteries
dry cell
batteries
rechargeable batteries
fuel cells
hydrogen powered cells
what are dry cells
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.
what are some factors affecting the voltage produced by the cell
the type of electrode and electrolyte. the higher the difference in reactivity between the 2 metals, the higher the voltage produced
how can you make a cell
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
what is a battery
a battery contains 2 or more cells connected in series
what is a rechargeable battery
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.
what is a rechargeable battery
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.
what are fuel cells
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
what are hydrogen powered vehicles
vehicles who use hydrogen as fuel instead of the normal oil
explain how hydrogen fuel cell works
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.
what are the advantages and disadvantages of hydrogen fuel cells.
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
what is the half equation for hydrogen reacting with hydroxide ions
2H2(g) + 4OH-(aq) —> 4H20(l) + 4e-
