paper 2

Question 1

how temperature increases rate of reaction (3)

Answer 1

1) particles move faster, more kinetic energy
2) collide more frequently
3) more particles have activation energy so more successful collisions

Question 2

how increasing concentration/ pressure increases rate of reaction (2)

Answer 2

1) more particles per unit volume
2) more successful collisions

Question 3

How increasing surface area of reactants increases rate of reaction (2)

Answer 3

1) increases surface area to volume ratio
2) particles will have more area to work on
3) so more successful collisions

Question 4

How using a catalyst increases rate of reaction (2)

Answer 4

1) provide an alternative reaction pathway
2) with a lower activation energy

Question 5

Le Chatelier’s principle for decreasing temperature

Answer 5

1) decrease in temperature, reaction will move in exothermic direction of reaction
2) so will get more products for exothermic reaction than endothermic one

Question 6

How dynamic equilibrium is reached (5)

Answer 6

1) in a closed system
2) as reactants react, their concentrations fall, so forward reaction slow down
3) more products are made, so their concentrations will rise so backward reaction speed up
4) eventually, the forward reaction will be going at exactly the same rate as the backward one
5) so the concentrations of the reactants and products won’t change

Question 7

Le chatelier’s principle for increasing temperature (2)

Answer 7

1) reaction will shift in endothermic direction
2) so more products for endothermic reaction than exothermic one

Question 8

Le chatelier’s principle for increasing pressure (2)

Answer 8

1) equilibrium try to reduce it
2) move in direction with fewer molecules of gas (use balanced symbol equation to see)

Question 9

Le chatelier’s principle for decreasing pressure (2)

Answer 9

1) equilibrium try to increase it
2) moves in direction with more molecules of gas (use balanced symbol equation to see)

Question 10

Le chatelier’s principle for increasing concentration of reactants (2)

Answer 10

1) try to decrease it
2) by making more products

Question 11

Le chatelier’s principle for decrease concentration of products (2)

Answer 11

1) try to increase it
2) reducing amount of reactants

Question 12

fractional distillation (6)

Answer 12

1) oil is heated until it evaporates
2) gases enter fractionating column and liquid part is drained off
3) in the column there is a temperature gradient (hot at bottom cool a top)
4) Longer chain hydrocarbons have high boiling points so condense back into liquids and drain out
5) shorter hydrocarbons have lower boiling points so condense and drain out nearer the top
6) crude oil has been separated out into different fractions containing a mixture of hydrocarbons

Question 13

how to test for alkenes (3)

Answer 13

1) orange bromine water is added to alkene
2) bromine water reacts with the alkene
3) colourless compound is formed and bromine water turns colourless

Question 14

steam cracking (3)

Answer 14

1) heat the long chain hydrocarbons so they are vapourised
2) mix the hydrocarbons with steam and heat to a very high temp
3) long chain molecules will split apart

Question 15

catalytic cracking (3)

Answer 15

1) heat the long chain hydrocarbons to vapourise them
2) pass the vapour over a hot powdered aluminium oxide catalyst
3) long chain molecules will split apart on the surface of the specks of catalyst

Question 16

earth’s early atmosphere (7)

Answer 16

1) first billions of years, intense volcanic activity that released lots of gases
2) early atmosphere made up of mostly CO2, with virtually no O2
3) volcanic activity also increased nitrogen, as well as water vapour and small amounts of methane and ammonia
4) water vapour condensed to form oceans
5) carbon dioxide decreased as it dissolved in oceans
6) dissolved C02 went through a series of reactions to form carbon precipitates that formed sediments on seabed
7) then marine animals evolved, their shells and skeletons containing some of the carbonates from these oceans

Question 17

describe and explain the formation of deposits of limestone,
coal, crude oil and natural gas (6)

Answer 17

1) when plants, plankton and marine animals die, fall to seabed and get buried by layers of sediment
2) over millions of years, become compressed and form sedimentary rocks, oil and gas and trapping the carbon within them
3) crude oil and natural gas are formed from deposits of plankton
4) these fossil fuels form reservoirs under the seabed when they get trapped in rocks
5) coal is a sedimentary rock made from thick plant deposits
6) limestone is a sedimentary rock made mostly of calcium carbonate deposits from shells and skeletons of marine animals

Question 18

How oxygen increased in Earth’s atmosphere (6)

Answer 18

1) algae evolved first around 2.7 billion years ago
2) then over the next billions of years so did green plants
3) they absorbed carbon dioxide from the atmosphere to carry out photosynthesis
4) this meant they could also produce oxygen
5) as oxygen levels increased over time, more complex life could evolve
6) eventually about 200 million years ago, the atmosphere reached the levels it is at today

Question 19

the effect of greenhouse gases on the atmosphere/ climate change (6)

Answer 19

1) the sun sends short wavelength radiation to the earth
2) long wavelength radiation then gets reflected back off the earth
3) long wavelength radiation is thermal radiation
4) greenhouse gases absorb this long wavelength radiation
5) they re-radiate it in all directions
6) therefore resulting in the warming of the earth’s surface (the greenhouse effect)

Question 20

how sulfur dioxide is released into the atmosphere as acid rain (4)

Answer 20

1) released during the combustion of fossil fuels
2) that contain sulfur impurities
3) as the sulfur in the fuel becomes oxidised
4) gas then mixes with water in clouds they form dilute sulfuric acid and falls as acid rain

Question 21

How nitrogen oxides are released into atmosphere as acid rain (4)

Answer 21

1) reaction between nitrogen and oxygen in the air
2) caused by the heat of burning
3) nitrous oxides then created
4) gas then mixes with water in clouds they form dilute nitric acid and falls as acid rain

Question 22

bioleaching (4)

Answer 22

1) bacteria are mixed with the low grade ore
2) the bacteria carry out chemical reactions and produce a solution called a leachate
3) this contains the metal compound we want
4) can then be extracted using electrolysis or displacement using scrap iron

Question 23

phytomining (5)

Answer 23

1) plants are grown in soil containing metal compound we want
2) plants absorb the metal compound as they concentrate it within their tissue
3) plants are then harvested and burned
4) ash contains relatively high concentration of the metal compound
5) can be extracted using electrolysis or displacement using scrap iron

Question 24

how glass can be recycled (2)

Answer 24

1) glass is separated by colour or chemical composition
2) glass is crushed and then melted to be reshaped for use in other glass products

Question 25

stages of a LCA (life cycle assessment (5)

Answer 25

1) getting/ extracting raw materials
2) manufacturing and packaging
3) using the product
4) product disposal
5) transportation between every stage

Question 26

how to obtain potable water from a fresh water source (4)

Answer 26

1) find a freshwater source (rivers, reservoirs, lakes)
2) filtration using wire mesh
3) sand and gravel bed to get out any other solid bits
4) sterilisation to kill harmful bacteria or microbes using chlorine gas, ozone or UV light

Question 27

reverse osmosis (3)

Answer 27

1) salty water is forced at a high pressure
2) over a semi permeable membrane
3) the salt is filtered out

Question 28

how waste/ sewage water is treated

Answer 28

1) the sewage is screened to remove large bits of material
2) stands in a settlement tank and undergoes sedimentation
3) separates sludge from the effluent
4) effluent in sedimentation tank is removed
5) treated by aerobic digestion - air is pumped through water to encourage aerobic bacteria to kill harmful bacteria
6) sludge in sedimentation tank is removed and transferred into large tanks
7) gets broken down anaerobically by bacteria
8) anaerobic digestion releases methane gas - can be used as an energy source
9) remaining digested waste can be used as fertiliser
10) for wastewater containing toxic substances, chemicals are added, UV radiation or usage of membranes