GCSE Paper 2 Flashcards
What is the general formula for an alkane?
CnH2n+2
What is the term for a group of compounds that react in a similar way?
Homologous series
What is a saturated compound? Refer to hydrocarbons
Each carbon atom form 4 single covalent bonds.
What are the first 4 alkanes?
Methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10)
How does the length of a hydrocarbon affect its properties? (3)
Shorter hydrocarbons are more runny
Shorter hydrocarbons are more volatile (lower boiling points)
Shorter hydrocarbons are more flammable
What is complete combustion?
When there is plenty of oxygen and the only waste products are CO2 and water
What is the word equation for the complete combustion of a hydrocarbon?
Hydrocarbon + oxygen -> carbon dioxide + water
Balanced symbol equation for the complete combustion of methane
CH4 + 2O2 -> CO2 + 2H2O
How is crude oil formed?
From the remains of plants and animals, mainly plankton.
What 6 products come from the fractional distillation of crude oil? (Top to bottom). Include the lengths of the hydrocarbons
LPG (liquified peteolem gas, mostly propane and butane) - 3
Petrol - 8
Kerosene -15
Diesel - 20
Heavy fuel oil (heavy fuel or lubricant oil) -40
Bitumen
What are some modern use of oil? (2)
Fuel for most modern transport
Petrochemical industry uses it to make polymers and lubricants etc
What is the test for alkenes?
Orange bromine water turns colourless at the presence of alkenes
What kind of reaction is cracking?
Thermal decomposition (breaking molecules down by heating them)
What is the chemical equation for cracking decane
Long hydrocarbon Decane (C10H22) -> Shorter hydrocarbon Octane (C8H18) + Alkene Ethene (C2H4)
Define purity
A substance that only contains one compound or element and has not been mixed
What is a formulation?
A mixture with a precise purpose that is made by following a formula.
Give an example of a formulation
Paint is a formulation composed of the Pigment, Solvent, Binder and additives
What industry uses important formulations?
Pharmeceuticals
Def chromatography
An analytical method used to seperate the substances in a mixture.
What are the two phases of chromatography?
Mobile phase - when the molecules can move. Could be liquid or gas
Stationary phase - where they cant move. Could be a solid or thick liquid
How can you identify a pure substance with chromatography?
Only one spot will be made. The solute will not split because it is only made up of one thing.
What two things determine how long molecules spend in the two phases of chromatography?
How soluable they are in the solvent
How attracted they are to the paper
What is the result of a chromatoraphy experiment called?
A chromatogram
What is the Rf value?
The ratio of the distance travelled by the solute to the solvent
What is the test for chlorine?
Bleaches damp litmus paper
What is the test for oxygen?
Relights a glowing splint
What is the test for carbon dioxide?
Turns limewater cloudy
What is the test for hydrogen?
Squeaky pop test
What are the three stages of the creation of the atmosphere?
Volcanoes gave out gases
Oceans, algae and green plants absorbed carbon dioxide
Green plants and algae produced oxygen
What happened when volcanoes gave out gases?
Volcanic activity released nitrogen, water vapour, methane and ammonia
What happened when oceans, algae and green plants absorbed CO2
Lots of CO2 dissolved into the oceans
Green plants and algae evolved to carry out photosynthesis
Some of this carbon has become locked up in rocks and fossil fuels
How long ago was it that the atmosphere reached approximately 80% nitrogen and 20% oxygen?
200 million years
Describe the greenhouse effect
Short wavelength radiation from the sun passes into the atmosphere and is reflected as long wavelenght radiation which is absorbed and re-radiated by greenhouse gases in all directions.
Name 4 human activities that impact the greenhouse effect
Deforestation
Burning fossil fuels
Agriculture (more methane)
Creating waste e.g. landfill
4 consequences of climate change
Melted ice caps and rising sea levels. Flooding and coastal erosion
Changes in rainfall patterns
Frequency and severity of storms may increase
Changes in temp and water availability may affect wild animal distribution
Def carbon footprint
All the greenhouse gases and carbon dioxide emmissions released over somethings full life cycle.
How can you reduce a carbon footprint? (5)
Renewable or nuclear energy sources
Use more efficient processes to conserve energy and reduce waste
People could be taxed based on their emissions
Governments could put caps on emmissions for companies
Carbon capture
Why is reducing carbon footprints difficult?
Theres lots of work to be done on more efficient alternative technologies
It could impact economic growth
Hard to make international agreements as others might not do the same
Lifestyle changes are required
What other gases do you get from burning fossil fuels?
Nitrogen oxides
Sulfur dioxide
Carbon monoxide
Wgat problems can particulates of incomplete combustion cause?
Inhaling some gases like carbon monoxide can be toxic
They can create more clouds which causes global dimming
What problems can carbon monoxide cause?
It can stop oxygen from being carried in the blood by binding to haemoglobin
It is colourless and odourless so is very hard to detect
What is bioleeching?
Using bacteria to convert copper compounds into soluable compounds, separating the ore in the process. The leachate contains copper ions that can be extracted
What is phytomining
Growing plants in soil containing copper. The plants cant use the copper so it builds up in the leaves. The ash of the plants then contains soluable copper compounds
Why is metal recycling important?
It costs much less energy than mining new resources
How is glass recycled?
It is seperated by colour or composition
It is crushed and melted
It is molded into new products. It could also be used for other products such as glass wool for insulation
What are the four parts of a life cycle assesment
Getting the raw materials (extraction and processing)
Manufacture and packaging (energy, pollution and fumes, waste created)
Using the product (emmissions, also how long it can be used for)
Disposal (landfill, transportation energy, incineration pollution)
What problems are there with life cycle assesments?
Hard to give an effect of pollutants a quantitative value.
LCAs can be biased as it isnt all numbers
Selective LCAs can be done to only show some of a products impact
What three things are important in making potable water safe to drink?
Levels of dissolved salt are not too high
pH between 6.5 and 8.5
There aren’t any nasties (bacteria or microbes)
Where does most water in the uk come from?
Groundwater (mainly southeast)
What are the two processes of water purification?
Filtration (wire mesh then gravel or sand to filter solid bits)
Sterilisation (to kill bacteria and microbes by bubling chlorine through it or using ozone or uv light)
How can very dry countries get potable water?
Desalination of seawater
What 2 processes could be used to desalinate seawater?
Distillation
Reverse osmosis
How would you distil seawater?
Test the pH (neutralise if not around 7)
Start the bunsen burner
As the water evaporates, it cools in the condenser
Collect the water in a beaker
Retest the pH
Why is it not practical to do distillation or reverse osmosis of seatwater?
They require loads of energy, are impractical and really expensive
Where does wastewater come from?
Homes (showers, toilets etc)
Agricultural systems
Sewage (has to be treated first)
Industrial processes (contains chemicals so multiple treatment stages)
Describe the process of sewage treatment
Sewage is screened to remove large bits
It is allowed to stand in sedimentation as heavy bits sink (sludge) and lighter effluents rise
The effluent is removed and treated by biological aerobic digestion
The sludge is removed and broken down by anaerobic digestion (releases methane)
For toxic substances, waste may be treated with uv radiation or membranes
Give an example of a slow, medium and fast reaction
Iron rusting
Magnesium reacting with acid
Burning
What two things does the rate of reaction depend on according to collision theory?
The collision frequency
The energy transferred per collision
What four things determines rate of reaction
Temperature
Concentration/pressure
Surface area
Catalysts
Why does a temp increase increase the rate of reaction
Particles move faster and collide more frequently and with more energy
Increases the amount of particles with the energy sufficient to surpass the activation energy
How does concentration/pressure affect rates of reaction?
An increase in particles that are reacting in the same volume of solvent or smaller space causes an increase in the frequency of collisions between particles
Why does surface area affect rate of reaction?
Breaking down a solid increases the surface area to volume ratio meaning for the same volume of solid there is more area for particles to work on causing more frequent collisions
How does a catalyst increase rate of reaction?
The use of a catalyst decreases the activation energy required by provoding an alternate reaction pathway with a lower activation energy
What is the formula for rate of reaction?
Amount of reactant used or product formed (cm3 or g) / time taken (s)
What three ways can you measure rate of reaction?
Precipitation and colour change (colourless liquid turns cloudy)
Change in mass (measure the difference. This us most accurate method)
Volume of gas given off (use gas syringe to measure gas given off in a certain amount of time)
How can you use the reaction of magnesium and hydrochloric acid to measure effect of concentration?
Place HCl in a flask and add magnesium ribbon.
Plug the flask with cotton wool
Start a stopwatch and take readings of the mass at regular intervals
Plot results on graph
Repeat with different concentrations of acid. Keep magnisium ribbon the same
How can you use sodium thiosulphate and HCl to measure effect of concentration
Add dilute sodium thiosulphate into a flask
Place it on paper with a cross drawn on it
Add dilute HCl and start a stopwatch
Stop the timer when the cross is no longer visible
Repeat with different concentrations
What is a main requirement of a reaction to reach equilibrium?
It must be in a closed system
What conditions affect the position of equilibrium?
The temperature
The pressure (only affects gases)
The concentration (of both reactants and products)
What is la chatiliers principle?
If you change the conditions of a reaction, the system will try to counteract that change?
How does raising temp affect a reversible reaction?
If the reaction one way is endothermic, equilibrium will lie to that side
How does raising pressure affect a reversible reaction?
The system will try to make more products with less molecules to reduce the pressure
Why is the cotton wool used in the experiment measuring gas release?
It lets carbon dioxide escape but stops any spray and excess mass being lost
Why do you use marble chips when measuring gas given off and not magnesium?
Marble chips and acid creates carbon dioxide which is heavier and easier to measure than hydrogen given off by magnesium and acid
