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Chemistry Paper 2 Flashcards

1
Q

Define molecular formula

A

Shows the total number of each type of atom in a compound

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2
Q

Define empirical formula

A

Shows the simplest whole number ratio of each type of atom in a compound

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3
Q

How do you calculate empirical formula?

A

Divide each elements’ percentage in the formula by its mass then divide both by the smallest answer

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4
Q

How do you work out relative formula mass?

A

Add up each of the elements’ relative atomic mass in the formula

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5
Q

What is Avogadro’s number?

A

6.02 x 10^23 particles ,one mole

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6
Q

What is the mass of one mole of a substance?

A

It’s relative formula mass in grams

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7
Q

Formula for moles?

A

Mass in grams divided by relative formula mass

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8
Q

What is 1litre equal to in cm^3 and dm^3?

A

1000cm^3, 1dm^3

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9
Q

What does electroplating do?

A

Coat a cheap metal with a thin layer of an expensive metal

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10
Q

Give three reasons aluminium is useful?

A

Low density (used to build airplanes), malleable, ductile

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11
Q

What colour does Cl2 bleach damp litmus paper?

A

White

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12
Q

What is a use of chlorine?

A

To make disinfectants and antiseptics

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13
Q

What is a use of hydrogen?

A

To make margarines

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14
Q

What is the first thing to check when improving a method?

A

The chemicals used

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15
Q

How do you adapt equipment in an experiment to prevent heat loss and why is this important?

A

Use a lid. Prevents temperature decrease which would impact rate of reaction because temperature is a factor which changes rate. The lower the temperature, the less energy given to particles which results in less successful collisions

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16
Q

What do catalysts do?

A

Decrease activation energy barrier by speeding up a reaction without being used up in the reaction. They do this by providing an alternative reaction pathway with a lower activation energy

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17
Q

How does making particles smaller affect surface area of a substance and number of collisions?

A

This increases surface area to volume ratio of a substance because there are more particles in the same volume so the particles have more area to work on which results in more frequent collisions, meaning a higher rate of reaction

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18
Q

What happens to copper chloride solution in electrolysis?

A

Copper and hydrogen go to cathode, copper discharges first. Chloride and hydroxide go to anode, chloride (halide) discharges first. Hydrogen and hydroxide left in container

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19
Q

In electrolysis of aluminium, the electrolyte is aluminium oxide mixed with what other substance?

A

Cryolite

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20
Q

Why is cryolite added to aluminium oxide in electrolysis?

A

Lower the melting point of aluminium oxide

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21
Q

Why does the positive electrode get smaller in electrolysis when using a metal oxide?

A

The oxygen reacts with the positive carbon electrodes and they gradually burn away forming carbon dioxide

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22
Q

Define pure substance

A

A single element or compound

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23
Q

Define precipitate

A

An insoluble solid formed by addition of 2 soluble salts

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24
Q

What is a pure substance in everyday life?

A

Nothing else added to it

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25
Q

What is a positive test for hydrogen?

A

A lighted splint pops when put into a test tube of the gas

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26
Q

What is a positive test for oxygen?

A

A glowing splint relight when put into a test tube of the gas

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27
Q

What is a positive test for chlorine?

A

Chlorine bleaches damp litmus paper white (if you use blue litmus paper it may turn red for a moment because a solution of chlorine is acidic)

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28
Q

How do you observe the colour of a substance’s precipitate?

A

Place about 1cm depth of solution into a test tube, add a few drops of sodium hydroxide to solution, record colour of precipitate (if any), if precipitate is white add an excess of hydroxide to see if it redissolves

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29
Q

What colour precipitate was formed from aluminium after adding sodium hydroxide?

A

White, then it redissolved

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30
Q

What colour precipitate was formed from calcium after adding sodium hydroxide?

A

White but it didn’t re dissolve

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31
Q

What colour precipitate was formed from sodium after adding sodium hydroxide?

A

No precipitate

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32
Q

What colour precipitate was formed from magnesium after adding sodium hydroxide?

A

White but it didn’t redissolve

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33
Q

What colour precipitate was formed from copper after adding sodium hydroxide?

A

Blue

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34
Q

What colour precipitate was formed from cobalt after adding sodium hydroxide?

A

Blue then green then beige

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35
Q

What colour precipitate was formed from Zinc after adding sodium hydroxide?

A

White but it didn’t redissolve

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36
Q

What colour precipitate was formed from iron 3+ ion after adding sodium hydroxide?

A

Orange

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37
Q

What colour precipitate was formed from iron 2+ ion after adding sodium hydroxide?

A

Black

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38
Q

What colour precipitate was formed from potassium after adding sodium hydroxide?

A

No precipitate

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39
Q

What are fixed points?

A

The melting and boiling points of pure substances

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40
Q

Give an example of an impure substance

A

Salt in water

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41
Q

What affect do impurities have on a substance?

A

Lower bowling and melting points

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42
Q

What does paper chromatography do?

A

Seperate different dyes in a substance

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43
Q

What are E numbers?

A

Codes for different food colourings in foods

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44
Q

What is paper called in chromatography?

A

Stationary phase

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45
Q

What is the solvent (substance moving through paper) called in chromatography?

A

Mobile phase

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46
Q

How are the dyes of a substance separated in paper chromatography? 4 points

A

Substances in the dye constantly move between the mobile and stationary phase (an equilibrium is formed between the two phases), substances have different attractions to the stationary and mobile phases, substances which are more attracted to the mobile phase are more soluble and are carried further by the solvent and higher up the paper because the mobile phase moves through the stationary phase and anything dissolved in the mobile phase moves with it, components in a mixture normally separate through the stationary phase so long as they spend different amounts of time in the mobile phase

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47
Q

What 2 mistakes could someone make in the chromatography experiment and how could this affect results?

A

If the water level is higher than the baseline, the colours will run down into the water instead of up the paper. If the baseline is drawn in ink, the ink will run into the dyes and affect results

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48
Q

How do you calculate retention factor and what is it?

A

Distance travelled by pigment divided by distance travelled by solvent from baseline It is the ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent so the further through the stationary phase a substance moves the higher the Rf value

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49
Q

Define a formulation

A

A mixture containing an active ingredient (a chemical which delivers an effect) mixed with other things so it can easily be taken

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50
Q

Why must qualities be the same each time in a formulation?

A

To ensure the properties are the same. E.g paint is the same colour

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51
Q

Why do some tablets contain sugar?

A

To make them taste sweeter, making it easier to swallow

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52
Q

What type of reaction occurs when sodium hydrogencarbonate reacts with acid in the stomach to cure indigestion?

A

Neutralisation

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53
Q

Give the 5 stages of recycling glass bottles

A

Waste glass bottle, crushed, melted, moulded, new glass bottle

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54
Q

What substance could be added to a children’s medicine and why?

A

Sugar to make the medicine sweeter and therefore easier to swallow

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55
Q

Formula for moles?

A

Grams divided by relative formula mass

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56
Q

Define closed system

A

Stops anything entering or leaving the reaction e.g a closed bottle

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57
Q

Define dynamic equilibria

A

The stage in a reversible reaction where the rate of the forward reaction is equal to the rate of the backward reaction. The amount of product and reactant stays the same. Occurs in a closed system

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58
Q

What is le Chatelier’s principle?

A

If the equilibrium conditions change, the position of the equilibrium changes to counteract the change. Whatever you do, the equilibrium does the opposite

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59
Q

What does the equilibrium do if temperature is reduced?

A

The exothermic reaction is favoured (it moves to the side where heat is produced) as the system tries to get hot by producing heat

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60
Q

What does the equilibrium do if pressure is increased?

A

Only applies to equilibrium involving gases. Favours the side with the least number of molecules. Less molecules means a lower pressure

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61
Q

What does the equilibrium do if the concentration of a reactant is increased?

A

The system will no longer be at equilibrium so the system brings itself back to equilibrium by producing more products

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62
Q

What does the equilibrium do if the concentration of a product is decreased?

A

The system will no longer be at equilibrium so the system brings itself back to equilibrium by reducing the amount of reactants

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63
Q

What are the percentages of gases in the earths atmosphere?

A

21% oxygen, 78% nitrogen, carbon dioxide 0.04%, argon 1%, other gases trace amounts

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64
Q

What are the percentages of gases in mars?

A

Oxygen trace amounts, nitrogen 2%, carbon dioxide 96%, argon 2%, other gases trace amounts

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65
Q

What environmental problem does sulphur dioxide cause and what are 3 effects of this?

A

Acid rain which kills plants and damages buildings and makes metal corrode

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66
Q

How can acid rain be reduced in coal fired power stations?

A

Remove sulfur from the cual before combustion

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67
Q

What is the word equation for burning methane?

A

Methane + oxygen > carbon dioxide + hydrogen

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68
Q

How can we experiment to prove that the air contains 20% oxygen?

A

Light phosphorus on an evaporating dish in a trough of water under a bell jar. When the phosphorus is burnt and stops reacting the water rises by 20% meaning 20% of the gas has been used (this was oxygen)

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69
Q

What is the greenhouse effect?

A

Carbon dioxide and other gases in the atmosphere trap heat, keeping earth warm

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70
Q

How does the earth heat up?

A

Short wavelength infrared (thermal) radiation from the sun heats up the earth. As the earth cools longer wavelength radiation is trapped by gases in the atmosphere before it can escape back into space; the radiation stimulates bonds in the greenhouse gases molecules to vibrate, bend and stretch more vigorously. This increases the energy in the atmosphere and warms the earth

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71
Q

What percentage of the greenhouse effect does each gas account for?

A

82% carbon dioxide, 9% methane, 6% nitrous oxides, 3% fluorinated gases (CFCs)

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72
Q

What percentage of global warming does each land use account for?

A

32% electricity, 28% transportation 20% industry, 10% commercial and residential, 10% agriculture

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73
Q

Describe phase 1 of the earths atmosphere

A

4.5 billion years ago the earths surface was molten and as it cooled surface rocks formed. Volcanoes kept erupting, giving out steam and co2, the early atmosphere was nearly all co2 and volcanic activity also introduced nitrogen as well as water vapour, small amounts of methane and ammonia

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74
Q

Describe phase 2 of the earths atmosphere

A

When the water vapour condensed it formed the oceans which lots of carbon dioxide dissolved into and went through a series of reactions to form carbonate precipitates that formed sediments on the seabed. Marine plants later evolve; their skeletons and shells contained some of the carbonates from oceans, green plants and algae (which evolved first approx. 2.7million years ago) steadily converted Co2 into o2 by photosynthesis, nitrogen released by denitrifying bacteria

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75
Q

Describe phase 3 of the earths atmosphere

A

Build up of o2 killed off early organisms which allows evolution of complex organisms, 02 created the ozone layer (O3) after reacting in the presence of uv light- this filtered out most of the harmful UV rays from the sun, about 200 million years ago the atmosphere reached a composition similar to today (approx. 80% nitrogen and 20% oxygen and small amounts of other gases)

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76
Q

Where is some carbon trapped?

A

When plants and animals die they fall to the seabed and get buried by layers of sediment, become compressed over millions of years to form sedimentary rocks, oil and gas (fossil fuels) which trap carbon within them

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77
Q

How did nitrogen form?

A

Ammonia in the air reacted with oxygen to form unreactive nitrogen gas. More nitrogen formed by bacteria in the soil

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78
Q

Identify 3 greenhouse gases

A

Carbon dioxide, methane, water vapour

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79
Q

What would Earths atmosphere be like without carbon dioxide?

A

Average temperature would be about -19 and life could not have evolved as we know it in liquid water

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80
Q

What happens to the suns rays? 5 things

A

51% absorbed by earth, 4% reflected by earths surface, 20% scattered by clouds (global dimming), 19% absorbed by atmosphere and clouds, 6% scattered from atmosphere

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81
Q

How can we find out what climate was like in the past?

A

Use ice cores (ice sheets which have gases trapped inside) Scientists analysts trapped air to find the composition of gases in the atmosphere. Analysts suggest levels of carbon dioxide are higher than any time in the past 440,000 years

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82
Q

What is the relationship between carbon dioxide levels and global temperature?

A

as carbon dioxide levels increase, global temperature increases

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83
Q

What are nox gases?

A

Range of nitrous oxides

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84
Q

What is the symbol for laughing gas?

A

N2O

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85
Q

What can ozone do to a person?

A

Set off asthma

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86
Q

What happens to the earth when there are less flights?

A

The earth warms as there are less contrails to reflect the suns rays

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87
Q

Define carbon footprint of a product or service or event

A

The amount of carbon dioxide and other greenhouse gases emitted over its full life cycle

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88
Q

What is the carbon footprint of plastic?

A

4kg produces 24kg of Co2

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89
Q

What happens when hydrocarbons are burnt in plenty of air?

A

Carbon and hydrogen in the fuel are completely oxidised. They produce carbon dioxide and water

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90
Q

What happens when sulfur impurities are burnt and how can this be prevented?

A

Burn to form sulfur dioxide which can cause acid rain because it mixes with water in clouds to form dilute sulphuric acid. Sulfur can be removed from fuels before they are burned or sulfur dioxide can be removed from flue gas

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91
Q

What happens when you change the conditions in which hydrocarbon fuels are made?

A

Change the products made

92
Q

What happens at high temperatures in engines?

A

Nitrogen from the air reacts with oxygen to form oxides of nitrogen. These can cause breathing problems and can also cause acid rain because they mix with water in clouds to form dilute nitric acid

93
Q

Why is carbon monoxide so dangerous?

A

Colourless and odourless so you can’t tell you’re breathing it in. Your red blood cells pick up carbon monoxide and carry it around your body instead of oxygen, it takes up the sites on haemoglobin in red blood cells which usually bond to oxygen. A victim of carbon monoxide poisoning will be starved of oxygen get drowsy lose consciousness then die if not removed from the source

94
Q

How does global dimming occur?

A

When large molecules do not get burnt completely and tiny solid particles containing carbon and unburnt hydrocarbons are produced. These particulates get carried into the air ,travel into the upper atmosphere and reflect sunlight back into space

95
Q

Define yield

A

Amount

96
Q

How does adding a catalyst increase rate of reaction?

A

Decreases the activation energy barrier. More particles with energy to react means more successful collisions

97
Q

Why would a jar containing unused cobalt chloride papers need to be kept closed?

A

To prevent them reacting with carbon dioxide and water

98
Q

How much water does flushing a toilet use?

A

6 litres

99
Q

How much water does a dishwasher use?

A

16 litres

100
Q

How much water does a quick shower use?

A

23 litres

101
Q

How much water does a washing machine use?

A

50 litres

102
Q

How much water does a relaxing bath use?

A

75 litres

103
Q

What did the Egyptians do with water before drinking it?

A

Collected it from the Nile then left the mud and silt sit so they could pour off the water

104
Q

Define potable water

A

Safe to drink. Not pure water

105
Q

What does potable water contain?

A

Low levels of dissolved salts (potassium or calcium or fluoride) pH is around 6.5 and 8.5

106
Q

What is distilled water?

A

Pure water with no dissolved substances

107
Q

What happens to rainwater?

A

It dissolves some gases from the air as it falls to the ground then collects underground as groundwater in rocks called aquifers that trap water underground or in lakes and rivers as surface water

108
Q

Identify 4 steps to producing potable water

A

Choose fresh water supply, pass water through wire mesh screens to remove leaves and twigs (filtration), pass the water through beds of sand and gravel to trap solid particles (filtration), sterilise microbes by bubbling chlorine through it or using ozone (sterilising agents) and use UV lights to kill bacteria

109
Q

What do you do if there are no fresh water supplies available when trying to produce potable water?

A

Desalinate the saltwater by distillation (boiling water to leave behind salt) or reversing osmosis using membranes -salty water is passed through a membrane which only allows water molecules through so ions and larger molecules are trapped by the membrane

110
Q

Why is desalination expensive?

A

Requires a lot of energy so they are not practical for producing large quantities of fresh water

111
Q

Why can’t we drink groundwater or water from lakes?

A

They may contain harmful bacteria or chemicals as well as mud, sand and waste

112
Q

Why can’t we drink sea water?

A

High in salt (sodium chloride)

113
Q

What did Hippocrates make his patients do before drinking water?

A

Boil it to kill some bacteria

114
Q

Why do some water companies add fluoride to drinking water?

A

It is good for your teeth

115
Q

Why should water be filtered to make it potable?

A

To remove undissolved solids

116
Q

Why is adding chemicals to water supply controversial?

A

People aren’t given any choice over whether they consume it or not

117
Q

How do you test and distil water in a lab? 6 steps

A

Test the pH of the water using a pH meter and if the pH is too high or low neutralise it using acid or alkali, use a pH meter to tell you when the solution is between pH 6.5 and 8.5. Pour salty water into distillation apparatus, heat the flask from below so the water boils and forms steam to leave dissolved solids in the flask, steam condenses to form liquid water in the condenser and can be collected as it runs out. Retest pH of water to check it is between pH 6.5 and 8.5. Check if there are crystals in the container to tell whether there were salts in the water

118
Q

Where does water go after we use it in our homes?

A

Into the sewers and towards sewage treatment plants

119
Q

Identify 2 types of waste water agricultural systems produce

A

Slurry from animal farms, nutrient run off from fields

120
Q

What happens to waste water from agricultural and domestic systems?

A

Treated to remove any organic matter and harmful microbes which would pollute fresh water when it gets put back in and this would pose health risks

121
Q

What happens to waste water from industrial processes and why?

A

It has to undergo additional stages of treatment before it is safe to release into the environment because industrial waste water can contain harmful chemicals as well as organic matter

122
Q

How is sewage treated? 4 steps

A

Sewage is screened to remove large bits of material like twigs and also grit, stands in a settlement tank and undergoes sedimentation, effluent in the settlement tank is removed and treated by biological aerobic digestion, sludge from the bottom of the tank is removed and transferred into large tanks where it is broken down by bacteria by anaerobic digestion

123
Q

What do additional stages of treatment for waste water containing toxic substances?

A

Chemicals to precipitate metals, UV radiation or membranes

124
Q

Why is sewage treatment an alternative to desalination in producing fresh water?

A

Requires more processes however uses less energy

125
Q

Which radiation do greenhouse gases absorb?

A

Long wavelength (thermal) radiation reflected back off the earth but not incoming short wavelength from the sun

126
Q

Identify 4 activities which affect the amount of greenhouse gases in the atmosphere

A

Deforestation, burning fossil fuels (carbon that was locked up in these is released as CO2), agriculture (farm animals produce methane through their digestive processes), creating waste (landfill and waste from agriculture releases methane and CO2 when they decompose)

127
Q

What is the positive of greenhouse gases?

A

Without them our planet would be extremely cold, the greenhouse effect warms the planet enough to support living things

128
Q

How can climate change have dangerous consequences? 4 examples

A

Polar ice caps melt which causes a rise in sea levels, leading to coastal flooding and coastal erosion. Changes in rainfall patterns cause some regions to get too much or too little water which can affect the ability to produce food, the frequency and severity of storms may also increase, changes in temperature and amount of water affect wild species and lead to differences in their distribution

129
Q

How do fossil fuels form? 3 steps

A

When plants, plankton and marine animals die they fall to the seabed and get buried in layers of sediment, over millions of years they become compressed and from sedimentary rocks, oil and gas which trap carbon within them (helping keep it out of the atmosphere)

130
Q

What are crude oil and natural gas formed from?

A

From deposits of plankton, these fossil fuels form reservoirs under the seabed when they get trapped in rocks

131
Q

What is coal formed from?

A

Thick plant deposits

132
Q

What is limestone?

A

A sedimentary rock made mostly of calcium carbonate deposits from shells and skeletons of marine organisms

133
Q

What is sedimentation?

A

heavier suspended solids sink to the bottom to produce sludge while the lighter effluent floats on the top

134
Q

What is biological aerobic digestion?

A

Air is pumped through the water to encourage aerobic bacteria to break down organic matter and other microbes

135
Q

What is anaerobic digestion?

A

Breaking down organic matter and releases methane gas in the process which can be used as an energy source, remaining digested waste can be used a fertiliser

136
Q

Give 2 examples of natural resources

A

Cotton for clothing, oil for fuel

137
Q

What can natural products like rubber be replaced by?

A

Synthetic products like man made polymers

138
Q

Where is rubber extracted from?

A

Sap of a tree

139
Q

Give an example where agriculture provides conditions where natural resources can be enhanced for our needs

A

Development of fertilisers means we can produce a high yield of crops

140
Q

Define renewable resources

A

Resources which reform at a similar rate or faster than we use them

141
Q

How is timber a renewable resource?

A

Trees can be planted following a harvest and only take a few years to regrow

142
Q

Define finite resources

A

Resources which do not form quickly enough to be considered replaceable

143
Q

What happens to finite resources after they have been extracted? Give 2 examples

A

They undergo man made processes to provide fuels and materials necessary for human life. Crude oil undergoes fractional distillation to produce petrol, metal ores are reduced to produce pure metals

144
Q

Which has a lower energy density (MJ/m^3): timber or coal?

A

Timber

145
Q

Define energy density

A

The amount of energy stored in a given system, substance, or region of space per unit volume

146
Q

Identify 4 costs of extracting metal ores

A

Land scarring, destroying habitats, producing lots of waste, using loads of energy

147
Q

Identify 3 benefits of extracting metal ores

A

Useful products can be made, local people provided with jobs, money brought to area

148
Q

What is sustainable development?

A

An approach to development that takes into account the needs of the present society while not damaging the lives of future generations

149
Q

Why is extracting finite sources unsustainable?

A

Due to the amount of energy used and waste produced

150
Q

Why is processing finite resources into useful materials unsustainable?

A

Processes often use energy which Is made from finite resources

151
Q

What happens if people reduce how much they use of a finite resource? 2 things

A

The resource is more likely to last longer and the use of anything needed to produce them will be reduced

152
Q

Give an example of how chemists have developed/adapted processes that use lower amounts of finite resources and reduce damage to environment

A

Developed catalysts which reduce the amount of energy required for certain industrial processes

153
Q

Identify 2 ways to improve copper (a finite resource)’s sustainability

A

Extract it from low grade ores by bioleaching or phytomining

154
Q

What is bioleaching?

A

Bacteria used to convert copper compounds in the ore to soluble copper compounds which seperates out the copper from the ore in the process. The leachate (solution produced by process) contains copper ions which can be extracted by electrolysis or displacement with a more reactive metal

155
Q

What is phytomining?

A

Growing plants in soil which contains copper. The plants can’t use or get rid of the copper so it gradually builds up in the leaves. Plants are harvested, dried and burned in a furnace. The ash contains soluble copper compounds from which copper can be extracted by electrolysis or displacement

156
Q

What is the advantage and the disadvantage of bioleaching and phytomining?

A

Smaller impact on environment. Slow processes

157
Q

Why is it more sustainable to recycle a finite resource after it is worn out rather than replace it with new raw materials?

A

Mining and extracting metals takes lots of energy most of which comes from burning fossil fuels, recycling metals uses less energy than is needed to extract and mine new metal, recycling conserves the finite amount of each metal in the earth, recycling cuts down the amount of waste sent to landfill

158
Q

How are metals usually recycled?

A

Melting them and then casting them into the shape of the new product

159
Q

What can change depending on what the metal will be use for after recycling? Give an example

A

The amount of separation required. Waste steel and iron can be kept together as they can both be added to iron in a blast furnace to reduce the amount of iron ore required

160
Q

What is a blast furnace used for?

A

Extracting iron from its ore at a high temperature using carbon

161
Q

How can glass recycling help sustainability? 2 ways

A

Reducing amount of energy needed to make new glass products, reducing amount of waste created when used glass is thrown away

162
Q

How is glass usually separated before being recycled?

A

By colour

163
Q

What are the 2 steps to glass recycling?

A

Crushed then melted to be reshaped

164
Q

What is a purpose for glass in homes?

A

Insulating glass wool for wall insulation

165
Q

What does a company do if they want to manufacture a new product?

A

Carry out a life cycle assessment

166
Q

What does a life cycle assessment look at?

A

Every stage of a product’s life to assess the impact it would have on the environment

167
Q

Which 4 stages need to be considered in a life cycle assessment?

A

Extracting and processing raw materials, manufacturing and packaging and waste products, using the product and how many uses, product disposal

168
Q

Why is a life cycle assessment time consuming and expensive?

A

So much to take account of

169
Q

Give 4 facts which suggest plastic bags are better for the environment than paper bags

A

Plastic bags can be reused as shopping bags and as bin liners whereas paper bags are usually used once, paper bags produce more waste when manufactured, paper bags require more energy to manufacture, recycling plastic bags reduces use of energy sources in manufacturing

170
Q

Give 4 facts which suggest plastic bags are worse for the environment than paper bags

A

Produce more carbon dioxide when manufactured, paper bags are biodegradable, paper bags are sustainable as they are made from infinite resources (timber) but plastic bags are made from crude oil, plastic bags take up space in landfill and pollute land

171
Q

How are plastic bags manufactured?

A

Compounds needed to make plastic are extracted from crude oil by fractional distillation followed by cracking then polymerisation. Waste is reduced as other fractions of crude oil have different uses

172
Q

How are paper bags manufactured?

A

Pulped timber is processed using lots of energy. a lot of waste made

173
Q

Identify 3 problems with life cycle assessments

A

The effect of some pollutants is hard to give a numerical value to so LCAs are not objective methods as they can be biased to the person carrying out the experiment. Selective LCAs are biased as they can be written to support the claims of a company and give them positive advertising, not all environmental impacts can be written in an LCA

174
Q

How is glass to make new bottles produced?

A

When a mixture of sand, limestone, soda and recycled glass is heated to about 1600 degrees Celsius in a furnace. There are almost unlimited amounts of raw materials needed to produce this glass

175
Q

Why are glass milk bottles better than plastic milk bottles? 3 reasons

A

Glass bottles made from infinite resources whereas plastic is made from crude oil (finite), glass bottles can be reused around 24 times, almost 35% of the used glass is recycled whereas only about 5% of the used plastic is recyled

176
Q

What is the rate of a chemical reaction?

A

How fast the reactants are changed into products

177
Q

Identify 2 slow reactions

A

Chemical weathering, rusting of iron

178
Q

Identify a moderate speed reaction

A

Metal magnesium reacting with acid to produce a gentle stream of bubbles

179
Q

Identify 2 fast reactions

A

Burning, explosions (explosions all over in a fraction of a second)

180
Q

Why do lines showing rate of reaction on a graph get less steep over time?

A

Reactants are used up

181
Q

Identify 4 factors a chemical reaction depends on

A

Surface area, temperature, concentration of a solution/ pressure of a gas, presence of a catalyst

182
Q

Why does increasing temperature increase rate of reaction?

A

Particles all move faster and if they move faster they will collide more frequently and will have more energy so more collisions will have enough energy to make the reaction happen

183
Q

Why does increasing concentration/pressure increase rate?

A

More particles knocking about in the same volume of solvent so collisions between reactant par fuels are more frequent

184
Q

How can you record precipitation and colour change?

A

If the initial solution is transparent and the product is a precipitate which clouds the solution observe a mark through the solution and measure how king it takes to disappear. If the reactants are coloured and the products are colourless you can time how long it takes for the solution to lose its colour. This is very subjective as different people may not agree over the exact point when the mark disappears or when the solution loses all colour

185
Q

Define turbidity

A

Cloudiness of a solution

186
Q

How can you measure change in mass (usually a gas given off)? 5 steps

A

Place the solution in a conical flask on a mass balance, put cotton wool in top of flask to stop acid spitting and let gas escape (disadvantage gas is released straight into room), as gas is released mass disappearing is measured on the balance, quicker the reading drops the faster the reaction, if you take measurements at regular intervals you can plot on a graph

187
Q

How can you measure volume of gas given off? 3 steps

A

Place a gas syringe in a bung in the top of a conical flask to measure volume of gas, more gas given off by each time interval the faster the reaction, gas syringes five volumes accurate to the nearest cm^3 and you can plot a graph if you take measurements at regular intervals

188
Q

How can you measure the reaction between hydrochloride acid and magnesium? 4 steps

A

Add a set volume of dilute hydrochloric acid to a conical flask, add some magnesium ribbon to the acid , attach an empty gas syringe to the flask,start the stopwatch abs take readings of the gas volume at regular intervals to plot a graph

189
Q

How do HCl and Sodium thiosulphate react with sulphur and how to measure this?

A

Form a yellow precipitate of sulfur. Add set volume of dilute sodium thiosulphate to conical flask, place flask on top of paper with black cross on it, add some dilute hydrochloric acid to flask, time how long it takes for cross to disappear through cloudy sulphur using stopwatch

190
Q

What does a rate of reaction graph show on each axis?

A

Amount of product formed/reactant used up on y axis, time on x axis

191
Q

How do you work out rate of reaction on a graph?

A

Work out gradient of the curve at that point by drawing a tangent

192
Q

What is the difference between the equilibrium lying to the right and lying to the left?

A

When it lies to the right the concentration of products is greater but when it lies to the left the concentration of reactants is greater

193
Q

Why is heating blue hydrated copper sulphate crystals an endothermic reaction?

A

It drives the water off and leaves white anhydrous copper sulphate powder

194
Q

Define hydrocarbons

A

Compound formed from only hydrogen and carbon atoms

195
Q

Define alkane

A

Saturated hydrocarbons (each carbon atom has four single covalent bonds), their general formula is CnH2n+2. A homologous series (group of organic compounds that react similarly)

196
Q

Identify the first 4 alkanes

A

Methane Ethane Propane Butane

197
Q

How do properties change as a carbon chain increases in length?

A

The shorter the carbon chain, the more runny (less viscous/gloopy), the more volatile (it turns into a gas at a lower temperature) so has a lower boiling point, the more flammable

198
Q

Why are long hydrocarbon chains broken down?

A

Short chain hydrocarbons are in higher demand as fuels , they have lower boiling points so can be used as bottled gases (stored under pressure as liquids in bottles) and they are more flammable

199
Q

What happens in complete combustion of a hydrocarbon in oxygen?

A

Only waste products are carbon dioxide and water vapour, lots of energy is released because hydrogen and carbon are oxidised

200
Q

Why are hydrocarbons used as fuels?

A

Due to the amount of energy released when they combust completely

201
Q

How is crude oil formed?

A

It is a fossil fuel formed from the remains of plants and animals (mainly plankton) that died millions of years ago and were buried in mud then turned to crude oil over millions of years with high temperature and pressure which can be drilled up from rocks where it is found

202
Q

Define finite resource

A

Non renewable fuels like coal, oil and gas which take so long to make that they are being used up faster than they are being formed

203
Q

What is crude oil?

A

A mixture of lots of different hydrocarbons most of which are alkanes which are separated by fractional distillation

204
Q

How does fractional distillation work? 6 steps

A

Crude oil is heated until most of it turns into gas, gases enter a fractionating column and the liquid bit is drained off, in the column there is a temperature gradient (hot at bottom and cooler at top), longer hydrocarbons have higher boiling points so condense back into liquids and drain out of the column early on when they are near the bottom, shorter hydrocarbons with lower boiling points condense and drain out much later on near to the top of the column where it is cooler, this seperates the crude oil mixture into different fractions (each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms and have similar boiling points

205
Q

How is crude oil important in modern life? 2 ways

A

Petrol/diesel/kerosene/heavy fuel oil/liquid petroleum gas all come from crude oil so it provides fuel for modern transport, petrochemical industry uses some chemicals from crude oil as a feedstock to make new compounds for polymers/solvents/lubricants/detergents

206
Q

Why can you get such a large variety of organic compounds as products from crude oil?

A

Organic compounds are compounds containing carbon atoms and carbon atoms can bond together to form homologous series (groups which contain similar compounds with many properties in common)

207
Q

What are alkenes?

A

Unsaturated hydrocarbons (double bonds between carbon atoms) which can be used as starting material when making lots of other compounds and can be used when making polymers

208
Q

How can we test for alkenes?

A

Add orange bromine water to the alkene and a reaction occurs which results in a colourless compound being produced and bromine water being decolourised, however if the bromine water was added to an alkane no reaction would occur and the bromine water would remain bright orange because alkenes are more reactive

209
Q

How does cracking work?

A

Heat long chain hydrocarbons to vaporise them, pass vapour over a hot powdered aluminium oxide catalyst,, long chain molecules split apart on the surface of the specks of the catalyst (catalytic cracking). Another way to crack hydrocarbons if you vaporise them is mixing them with steam and then heating them to a very high temperature (steam cracking)

210
Q

What is thermal decomposition?

A

Breaking down molecules by heating them, an example is cracking

211
Q

How can you test the purity of a sample?

A

Measure its melting/boiling point and compare it with the melting/boiling point of the pure substance which you can find in a data book, the closer your measured value is the purer the substance

212
Q

What 4 things do impurities change about a substance?

A

They lower the melting point and increase the melting range of a substance and increase the boiling point and may result in your sample boiling over a range of temperatures

213
Q

Why are formulations important in the pharmaceutical industry?

A

By altering a pill’s formulation chemists can make sure it delivers the drug to the right part of the body at the right concentration, that it is consumable and has a long enough shelf life

214
Q

Identify 7 things formulations can be found in

A

Fertilisers, cleaning products, fuels, food, drink, cosmetics, metal alloys

215
Q

Positive test for carbon dioxide

A

Bubbling carbon dioxide through (or shaking carbon dioxide with) an aqueous solution of calcium hydroxide known as limewater causes the solution to turn cloudy

216
Q

Define mobile phase

A

Where molecules can move, always a liquid or gas

217
Q

Define stationary phase

A

Where molecules cannot move, can be a solid or a really thick liquid

218
Q

How can chromatography be used to see if a certain substance is present in a mixture?

A

Run a pure sample of the substance alongside the unknown mixture to see if one spot in the unknown mixture matches the pure sample and if the Rf values match which means the substance may be present. Test both using different solvents to see if the Rf values match up each time because solvent affects Rf value

219
Q

What factor affects Rf value?

A

The solvent

220
Q

What is the greenhouse effect?

A

Gases like carbon dioxide/water vapour/methane act like an insulating layer in the Earth’s atmosphere which allows the earth to be warm enough to support human life, all particles absorb long wavelength (thermal) radiation which is reflected off the earth but not incoming short wavelength from the Sun, then they re radiate in al directions including back towards earth, long wavelength is thermal radiation which results in warming of the earth

221
Q

Why are carbon footprints so hard to calculate?

A

There are so many different factors to consider for example the emissions released as a result of manufacturing all the parts of something then making it, also the emissions produced when you actually use it and finally dispose of it

222
Q

Identify 5 ways to reduce your carbon footprint

A

Renewable energy sources or nuclear energy instead of fossil fuels, more efficient processes which conserve energy and cut waste (which would decompose to produce methane), government could tax companies/individuals based on the amount of greenhouse gases they emit for example cars could be taxed which may encourage people to buy more fuel efficient cars, governments can put a cap on emissions of all greenhouse gases that companies make then sell licenses for emissions up to that cap, CO2 capture and storage technology captures it before it is released into the atmosphere the it can be stored deep underground in cracks in rock such as old oil wells

223
Q

What are 5 problems with cutting CO2 emissions?

A

Carbon capture and storage is relatively new idea so the technology is at the developmental stage at the moment, many renewable energy technologies like solar panels are still quite expensive so cannot be used widely, governments in developing countries are worried about reducing carbon emissions by making changes that could limit economic growth of the country, hard to make international agreements as most countries don’t want to sacrifice their economic growth if others won’t do the same, there isn’t enough education about why changes to individual’s lifestyles are necessary and how to make them

224
Q

Identify 3 ways an individual can reduce their carbon footprint

A

Cycle or walk instead of using a car, reduce how much they use air travel, do anything to save energy at home like turning down the heating

225
Q

What happens when fossil fuels are burned? 3 points

A

They contain hydrocarbons so carbon and hydrogen in these compounds are oxidised during combustion so carbon dioxide and water vapour are released back into the atmosphere, when there’s plenty of oxygen all the fuel burns (complete combustion) but when there is not enough oxygen incomplete combustion occurs, under these conditions solid particles made up of soot (carbon) and unburned hydrocarbons are released and carbon monoxide can be produced along with carbon dioxide

226
Q

What 2 problems can particulates in the air cause?

A

If they are inhaled they get stuck in the lungs and cause damage which leads to respiratory problems, particulates and clouds they help to produce reflect sunlight back into space which means less light reaches the earth which causes global dimming

227
Q

What are natural resources?

A

Anything which forms in the air, sea or earth without human input

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