GCSE AQA Combined Science Chemistry

C8 1) What is required for a reaction to happen?

a successful collisions

C8 2) How can you use a graph to calculate the rate of reaction?

calculate gradient (on a curve tangent)

C8 3) What four things can speed up the rate of reaction?

temperature, concentration, surface area and catalyst

C8 11) What formula is used to calculate the rate of reaction?

amount of product used or amount of product formed / time

C8 12) What would a line with negative gradient look like?

line would go down

C8 4) What 3 methods can be used to find out the rate of reaction?

measure colour change / measure volume of gas produced / measure change in mass

C8 4) How can you increase the rate of reaction?

increase collisions / increase energy

C8 8) How does increasing surface area increase the rate of reaction?

larger surface area quicker reaction rate

C8 14) Why is the rate of reaction increased if you crush up solids?

larger surface area quicker reaction rate

C8 13) What is the minimum amount of energy that particles must have before they react call?

activation energy

C8 15) How do you increase the surface area of a solid?

crush it

C8 5) Put these in order of larger surface area - small , medium and large marble chips

small

C8 5) How does temperature increase the rate of reaction?

more energy / move quicker / collide more frequently - more successful collisions

C8 6) When increasing the temperature, at the end of the reaction why is no more product made?

temperature does not affect amount of product made

C8 6) How does concentration increase the rate of reaction?

more particles = more collisions

C8 7) How does pressure increase the rate of reaction?

same number of particles but in a smaller space so more frequent collisions

C8 16) How do you investigate the effect of changing concentrations?

by reacting marble chips with differnet concentrations of hydrochloric acid

C8 17) State three ways you can measure the rate of reaction?

measure colour change / measure volume of gas produced / measure change in mass

C8 9) How do catalysts speed up the rate of reaction?

lower the activation energy by providing alternative pathway for reaction without being used up.

C8 10) Give an example of a biological catalyst.

Enzymes that break down proteins into amino acids.

C8 18) Why are catalysts important in industry?

save money as otherwise you'd have to work at high temperatures and pressures / save environment

C8 19) Why are catalysts often used as powders?

increase their surface area to volume ratio. Speed up collisions

C8 20) True or false: the catalyst does not get used up in the reaction

true

C8 21) True or false: you can use the same catalyst for all reactions

false

C8 22) What is a reversible reaction?

the products of the reaction can react to make the orignal reactants

C8 23) How can you represent a reversible reaction

C8 24) Give an example of a reversible reaction

ammonium chloride to ammonia and hydrogen chloride, hydrated copper

C8 25) What is the relationship between the amount of energy transferred in each direction of a reversible reaction?

it is the same

C8 26) In a reversible reactoin, if one reaction is exothermic the other reaction is?

endothermic

C8 27) In a reversible reaction, if one reaction is endothermic the other reaction is?

exothermic

C8 28) What do we mean by equilibrium?

the reactants are making products at the same rate the products are making reactants - no change in amount of products and reactants

C8 29) what happens when you start with just the reactants and a reversible reaction in a closed system?

it reaches equlibrium

C8 36) How does decreasing concentration affect an equilibrium?

shifts to add what has been added

C8 35) How does increasing concentration affect an eqiulibrium?

shifts to get rid of what has been added

C8 30) What is Le Chatelier's Principle?

whenever you introduce a change in conditions to a system at equilibrium, the position of equilibrium shifts to cancel out the change

C8 31) How does increasing pressure affect an equilibrium?

shifts to decrease pressure - reaction shifts in favour of producing less gas particles

C8 32) How does increasing temperature affect an equilibrium?

favours the endothermic reaction

C8 33) How does decreasing temperature affect an equilibrium?

favours the exothermic reaction

C8 34) How does decreasing pressure affect an equilibrium?

shifts to increase pressire - reaction shifts in favour of producing more gas particles

C9 1) What is crude oil?

many different compound - mostly hydrocarbons

C9 2) What are hydrocarbons?

compounds that only contain hydrogen and carbon

C9 3) What are alkanes?

saturated hydrocarbons

C9 4) What is the general formula for a alkane?

CnH(2n+2)

C9 5) What is the names of the first four alkanes?

methane. Ethane, propane and butane

C9 6) What is the formula for methane?

CH4

C9 7) What is the formula for ethane?

C2H6

C9 8) What is the forumale for propane?

C3H8

C9 9) What is the formula for butane?

C4H10

C9 10) What do we mean by volatility?

the tendency to turn into a gas

C9 11) What do we mean by viscosity?

how easiliy it flows

C9 12) What do we mean by flammability?

How easy it burns

C9 13) What are fractions?

separated into hydrocarbons with similar boiling points

C9 14) How does the size of a hydrocarbon affect its boiling point?

smallest have the lowest boiling points

C9 15) How does the size of a hydrocarbon affect its volatility?

smallest have higher volatility

C9 16) How does the size of a hydrocarbon affect its viscosity?

smallest havest highest viscosity

C9 17) How does the size of a hydrocarbon affect its flammability

smallest are more flammable

How is fractional distillation used to separate crude oil

separated into fractions and heated - oil heats and each condenses when it reaches its boiling point

C9 18) What is produced when hydrocarbons are burnt in a good supply of air?

carbon dioxide and water

C9 19) How do you test that carbon dioxide is formed from combustion?

turns limewater cloudy and the

C9 20) How do you test that water is formed from combustion?

water turns blue cobalt chlroride paper pink

C9 21) What is also formed in incomplete combustion?

carbon monoxide

C9 22) Why is carbon monoxide formed in incomplete combustion?

not enough oxygen to form carbon dioxide

C9 23) Why are larger hydrocarbon moleculesgo through the process of cracking?

not as in high demand as the smaller ones

C9 24) What do we call the process where large molecules are broken down into smaller ones?

cracking

C9 25) How does cracking work?

passing vapours over a hot catalyst or by mixing them with steam and heat them to avery high temperature

C9 26) What are alkenes?

compounds containing double bonds (unsaturated)

C9 27) How do alkanes differ from alkenes?

double bonds

C9 28) How do you test for alkenes?

react with organ bromine water turning it colourless

C12 1) What is a pure substance?

compound or element that contains only one substance

C12 2) What is an impure substance?

a mixture of two or more different elements or compounds

C12 3) How do you use melting points to distinguish between pure and impure substances?

pure substances melt and boil at specific temperatures - fixed points

C12 4) What are formulations?

useful mixtures made up in definite proportions designed to give a product the best properties possible to carry out its function

C12 5) How can chromatogrpahy be used to distinguish between pure and impure substances?

if mixture, more than one spot - single spot pure

C12 6) How does paper chromatogrpahy separate mixtures?

each component will have a different attraction for the mobile phase and the stationary phase so may travel further

C12 7) How do you measure Rf values from chromatograms?

distance moved by substance / distance moved by solvent

C12 8) How do you test for hydrogen?

a pop when you apply a light splint

C12 9) How do you test for oxygen?

relights glowing splint

C12 10) How do you test for carbon dioxide?

turns limewater cloudy

C12 11) How do you test for chlorine?

bleaches dampl blue litmus paper white

C13 1) When do scientists believe the Earth was formed?

4.6 billion years ago

C13 2) What is one theory of house the Earth's early atmosphere was formed?

Volcanoes releaseding carbon dioxide, water vapour and nitrogen.

C13 3) When the Earth began to stabalise, what gas did the atmosphere mainly consist of?

carbon dioxide

C13 4) When do scientists believe life began on Earth?

3.4 billion years ago

C13 5) Why was algae so important to the Earth's atmosphere?

could photosynthesise - releasing oxygen

C13 6) What did the evolution of plants do to the Earth's atmosphere?

increased the levels of oxygen, decereased the levels of carbon dioxide

C13 7) What did the evolution of plants do to the Earth's atmosphere?

increased the levels of oxygen, decereased the levels of carbon dioxide

C13 8) How were fossil fuels formed?

remains of living organisms crushed by large scale movements and heated in Earth's crust

C13 9) How was coal formed?

thick deposits of plant materia, buried in the absence of oxyfen and compressed over millions of years

C13 10) How were crude oil and natural gas formed?

the remains of plankton deposit in muds and on the seabed. Covered in sediments and comrepssed over millions of years

C13 11) How did fossil fuels lead to a decrease of carbon dioxide in the atmosphere?

carbon becamse locked up

C13 12) How are carbonate rocks formed?

carbon dioxide dissolving in oceans, reacting with metal oxides

C13 13) Why did the levels of ammonia and methane levlels decrease?

reacted with the oxygen

C13 14) What is the % of nitrogen in today's atmosphere?

78%

C13 15) What is the % of oxygen in today's atmosphere?

21

C13 16) What is the % of argon in today's atmosphere?

0.9

C13 17) What is the % of carbon dioxide in today's atmosphere?

0.04

C13 18) How does the greenhouse effect operate?

molecules absorb energy radiated by the Earth as it cools down. This increases the story of energy of the gas in the atmosphere and warms the Earth

C13 19) State two greenhouse gases

carbon dioxide, water vapour

C13 20) Why have carbon dioxide levels recently started to rise?

burning of fossil fuels / deforestation

C13 21) Some scientists argue against the idea that global warming has started. Why?

rises observed are due to natural variations that have always happened