C1 Flashcards
(81 cards)
0
Q
Name three properties of fossil fuels.
A
- Formed naturally - over millions of years
- Finite & non-renewable - used far faster than can be supplied
- Easily extracted
1
Q
Give three example of types of fossil fuels.
A
- Crude oil
- Natural gas
- Coal
2
Q
Problems with transporting crude oil, found in the earth’s crust and pumped to the surface, via pipelines or oil tankers?
A
- Accidents cause spills
- Oil floats on the sea’s surface as a slick and damages wildlife and beaches
- For example, it can stick birds wings together
- Detergents are used to break up oil slicks but these chemicals are toxic and harm or kill wildlife
3
Q
Different hydrocarbons have different boiling point which means crude can be…
A
Separated into useful fractions (parts) that contain mixtures of the hydrocarbons with similar boiling points. This is known as fractional distillation.
4
Q
During fraction distillation, crude oil is heated in a fractionating column which has a temperature gradient makes it hotter at the bottom than at the top. Where do fractions with high and low boiling points leave?
(4 points)
A
- Fractions with low boiling points leave at the top of the column
- Fractions with high boiling points leave at the bottom of the fractionating column
- Lower boiling point = short chain hydrocarbon
- Higher boiling point = long chain hydrocarbon
5
Q
What two groups do hydrocarbons fit into?
A
- Alkanes - saturated, single bond
2. Alkenes - unsaturated, double bond
6
Q
Large alkane molecules can be broken down into smaller, more useful alkane and alkene molecules (known as cracking). What things does this process need?
A
- Catalyst
- High temperature
- High pressure
- Under atmospheric pressure
7
Q
What is a product from naphtha though cracking?
A
- Petrol
* It can be used to make alkene molecules that may be used to make polymers
8
Q
Why is cracking so useful? (Make reference to demand and pressure on limited resources)
A
- Isn’t enough petrol in crude oil to meet demand
* Cracking changes parts of crude oil that can’t be used in additional petrol
9
Q
Complications surrounding extraction of oil.
A
- Companies have to work with lots of different countries to extract the oil
- Very valuable resource and can be a source of conflict and target for terrorism
10
Q
The forces in a hydrocarbon molecule are:
A
- strong covalent bonds between the atoms in a molecule
* weak intermolecular forces
11
Q
How does the strength of the forces between hydrocarbons affect its properties?
A
- longer hydrocarbon = stronger intermolecular forces
- When a liquid hydrocarbon is boiled, its molecules move faster and faster until all intermolecular forces are broken and it becomes a gas
- The bigger the molecules the stronger force of attraction between them
12
Q
Define: complete combustion (BLUE FLAME)
A
• When fuels react with oxygen (in air), they burn and release useful heat energy. This is called combustion, and it needs a plentiful supply of oxygen.
13
Q
What does a complete combustion of a hydrocarbon produce?
Show the word and symbol equation for complete combustion of methane.
A
- Carbon dioxide
- methane + oxygen —> carbon dioxide and water
- CH4(g) + 2O2(g) —> CO2(g) + 2H2O(l)
14
Q
Define: incomplete combustion (YELLOW FLAME)
A
• When fuels burn without enough oxygen, incomplete combustion occurs. Some heat energy is released but not as much as would be through complete combustion.
15
Q
What does incomplete combustion produce?
A
• Carbon monoxide - a poisonous gas which is why gas appliances should be serviced regularly
16
Q
Give the word and symbol equation for incomplete combustion of methane.
A
- methane + oxygen —> carbon monoxide + water
* 2CH4(g) + 3O2(g) —> 2CO2(g) + 4H20(l)
17
Q
When very little oxygen is present, what does the incomplete combustion of a hydrocarbon produce?
Show this with an example of methane.
A
- Carbon (soot) and water
- methane + oxygen —> carbon + water
- CH4(g) + O2 (g) —> C(s) + 2H20(l)
18
Q
What is a common test for the presence of carbon dioxide?
A
• Limewater - it turns milky if carbon dioxide is present
19
Q
Factors affecting your choice of fuel. (7 points)
A
- Energy value - how much energy is released per gram of fuel?
- Availability - how easy is it to obtain the fuel
- Ease of storage - how practical/easy is it to store the fuel?
- Toxicity - is the fuel (or combustion products) poisonous?
- Pollution - do the combustion products cause pollution?
- Ease of use - is it easy to control and is special equipment needed?
20
Q
Why when using a fuel would complete combustion be desirable?
A
- Less soot is produced
- More heat energy is released
- No carbon monoxide is made
21
Q
What is contributing to the growing demand for fossil fuels?
A
- Industrialisation of countries such as India and China.
* Growing population
22
Q
Today, clean dry air contains:
A
- 78% nitrogen
- 21% oxygen
- 1% other gases - including around 0.035% carbon dioxide
23
Q
How are levels of gas in the atmosphere controlled? (Carbon & nitrogen cycle)
A
- Respiration
- Combustion
- Photosynthesis
24
What two processes decrease oxygen levels and increase carbon dioxide levels?
* Respiration
| * Combustion
25
What does photosynthesis do to carbon dioxide and oxygen levels?
* They take in carbon dioxide and release oxygen
| * Photosynthesis and respiration balance out, so levels of carbon dioxide and oxygen in the air stay almost the same
26
What did the earliest atmosphere contain?
* Ammonia and carbon dioxide
| * These gases came from the inside the Earth and were released through volcanoes
27
How did the development of plants changes the level of gases in the atmosphere?
• Photosynthesis began and reduced levels of carbon dioxide and increased the amount of oxygen in the atmosphere
28
State the surrender theory as to how the Earth's atmosphere evolved.
1) Hot, volcanic Earth released gases from the crust into the atmosphere. So, initial atmosphere was made up of ammonia, carbon dioxide and water vapour.
2) The Earth cooled, surface temperature gradually fell to 100°C and the water vapour condensed to from liquid water. Newly formed oceans removed some carbon dioxide by dissolving the gas
3) The levels of nitrogen in the atmosphere increased as the nitrifying bacteria released nitrogen. This gas is relatively unreactive.
4) Oxygen levels in the atmosphere increase with the development of primitive plants that could photosynthesise. This removed carbon dioxide from the atmosphere, and added oxygen.
29
How is sulphur dioxide produced and what damage does it do to the environment?
• Made when fossil fuels that contain sulphur impurities are burned.
• Causes acid rain which:
- kills plants and aquatic life
- erodes stonework and corrodes ironwork
30
How is carbon monoxide formed?
• Poisonous gas formed from incomplete combustion in a car engine
31
How are oxides of nitrogen formed?
* Formed in car engines, they cause photochemical smog and acid rain
* Nitrogen and oxygen from the air react in the hot car engine to make nitrogen monoxide (NO) and nitrogen dioxide (NO2)
32
Describe three human factor's influence on the atmosphere
1. Burning of fossil fuels is increasing the amount of carbon dioxide in the atmosphere
2. Deforestation on large areas of the Earth's surface means the amount of photosynthesis is reduced so less carbon dioxide is removed from the atmosphere
3. Increase in world population has directly or indirectly contributed to the above factors
33
How can air pollution be reduced with a catalytic converter?
• carbon monoxide ---> carbon dioxide
carbon monoxide + nitrogen oxide ---> nitrogen + carbon dioxide
2CO + 2NO ---> N2 + 2CO2
34
Describe bonds found in hydrocarbons.
* carbon atoms can make four bonds each
* hydrogen atoms can make one bond each
* they have covalent bonds which means the carbon atoms share a pair of electrons with hydrogen atoms to make a covalent bonds
35
Why are alkanes saturated?
* They have only single covalent bonds
| * They have the maximum number of hydrogen atoms per carbon atom in the molecule
36
Why are alkanes described as being unsaturated?
• Each carbon atom isn't bonded to the maximum number of hydrogen atoms as they have at least in globule covalent bond e.g C = C
37
Molecular formulae that have one, two, three and four carbon molecules.
1. Meth
2. Eth
3. Prop All ending in either 'ane' or 'ene'
4. But
38
What does an alkene do to bromine water?
• it discolours the bromine water
39
What does an alkane do to bromine water?
• bromine water stays orange
40
Why are alkene so suitable for joining together to make polymers?
* Alkenes made by cracking are small molecules which can be used as monomers
* Double bonds in alkenes are easily broken, so monomers can be joined together to make polymers (large, long chain molecules)
* Molecules in plastic are called polymers
41
What is it called when alkenes are joined together to make a polymer?
What does this process require?
* Polymerisation
| * High pressure + catalyst
42
Properties and uses of polythene or poly(ethene).
```
Properties:
- light
- flexible
- easily moulded
- easily printed on
Uses:
- plastic bags - flexible & light
- moulded containers - the plastic is easily moulded
```
43
Properties and uses of polystyrene.
```
Properties:
- light
- poor conductor of heat
Uses:
- insulation - poor conductor of heat
```
44
Properties and uses of polyester
```
Properties:
- lightweight
- waterproof
- tough
- can be coloured
Uses
- clothing, the plastic can be made into fibres and is lightweight, waterproof and tough also can be coloured
- bottles, the plastic is lightweight and waterproof
```
45
Describe the bonds within PVC.
* Polymers such as PVC are made of very tangled very long chain molecules
* The atoms are held together by strong covalent bonds
46
Plastics that have weak forces between polymer molecules (intermolecular forces) have:
* Low melting points
| * Can be stretched easily because the polymer molecules can slide over each other
47
Plastics that have strong forces between polymer molecules (covalent bonds or cross-linking bridges) have:
* High melting points
| * Are rigid and can't be stretched
48
State the properties of nylon. (4 points)
```
• Lightweight
• Tough
• Waterproof
• Blocks UV light
- makes it ideal for outdoor clothing however it doesn't allow sweat to escape
```
49
How does Gore-Tex allow sweat (water vapour) to escape whilst preventing rain getting in?
* Nylon fibres are coated (laminated) with a membrane of polyurethane (PTFE)
* This makes the holes much small
* Coating is used with nylon because it's too weak to be used on it's own
50
Describe using landfill sites and the disadvantages of doing so.
* Most plastics are biodegradable
* Wastes valuable resources
* Landfill sites quickly becoming full
* Sites waste land
51
Describe burning polymers and the disadvantages of doing so.
* Produces air pollution
* Some plastics produce toxic fumes when they are burned, for example PVC produces hydrogen chloride gas when burning
* Wastes valuable resources
52
Describe recycling polymers and the disadvantages of doing so.
* Plastics need to be sorted and recycles separately
| * Can be time consuming and expensive
53
When a chemical change happens:
* New substances are formed
* There is an energy change
* It can't be referred easily
54
What happens when a protein-rich food such as egg or meat is heated?
* The protein molecules denature (change shape)
* Heat breaks down the cell wall and they become soft, this makes them easier to digest
* Change in texture and appearance
* It's an irreversible process
55
What chemical does baking powder contain? What happens when it is heated?
* Sodium hydrogen carbonate
| * It decomposes to make sodium carbonate and water, carbon dioxide is also given off
56
Give the word and symbol equation for the decomposition of baking powder.
sodium hydrogen ---> Sodium carbonate + water + carbon dioxide
carbonate *heat*
2NaHCO3 ---> Na2CO3 + H2O + CO2
57
Why is baking powder added to cake mixtures?
• As mixture is heated, the carbon dioxide gas is released causes e gas to rise
58
What is the job of an antioxidant?
• Stop food from reacting with oxygen in the air and to increase the shelf life
59
What is the job of a food colourant?
• Improve the appear and of food
60
What is the job of a food enhancer?
• Bring your the flavour of a food without adding a taste of their own
61
What is the job of an emulsifier?
• Helps to mix oil and water, which would normally separate e.g. Mayo
62
How does an emulsifier prevent oil and water from separating?
* An emulsifier has a hydrophilic end (water-loving) and a hydrophobic end (water-hating)
* The hydrophilic attracts to the water molecules
* The hydrophobic end attracts the oil molecules
* the attraction prevents the oil and water molecules from separating.
63
How is an ester made?
• By reacting an alcohol with an organic acid to produce an ester and water
64
What are desirable properties of a perfume? (5 points)
* Evaporate easily - so the scent travels to your nose
* Not be toxic - so it's doesn't poison you
* Not irritate - otherwise it would be uncomfortable on the skin
* Not dissolve in water - (insoluble) otherwise it would wash off easily
* Not react with water - otherwise it would react with sweat
65
What is meant by volatility?
* Evaporate easily
* Molecules are held together by weak forces of attraction
* weak bonds + high energy = high volatility
66
Define: soluble substances
• substances that dissolve in a liquid, e.g. Nail varnish is soluble in ethyl ethanoate (nail varnish remover)
67
Define: insoluble substances
• substances that don't dissolve in liquid, e.g. Nail varnish is insoluble in water
68
Define: solvent
• the liquid into which a substance is dissolved
69
Define: solute
• the substances that gets dissolved
70
Define: solution
• what you get when you kid a solvent and a solute, it will not separate out
71
Why does nail varnish dissolve in nail varnish remover and not water?
* the attraction between water molecules I stronger than the attraction between water and nail varnish molecules
* the attraction between the molecules in nail varnish is stronger than the attraction between the water and nail varnish molecules
72
Paint is a colloid. What does this mean?
• Colloids are made of small, solid particles that are mixed well (dispersed but not dissolved) with liquid particles
73
What is the job of a pigment?
• a substance that gives paint it's colour
74
What is the job of a binding medium?
• An oil that sticks the pigment to the surface that's it's being painted onto
75
What is the job of the solvent?
• Thins the thick binding medium and makes it easier to coat the surface
76
Two purposes of paint?
* Protect
| * Decorate
77
When does the paint dry?
• When the solvent evaporates
78
Describe the stages of an oil-based paint, such as gloss, drying.
1. Solvent evaporates away
| 2. The oil-binding medium reacts with oxygen in the air (oxidation reaction) as it dries to form a hard layer
79
What do thermochromic pigments do and where are they used?
• Change colour when heated
- kettles and cups to indicate change of temperature
- mood rings
- toys and cutlery for children to warn if food or bath water is too hot
80
What was the problem with the first 'glow in the dark' paint?
* Made using radioactive materials and used in items such as watches
* They exposed manufacturers to high levels of radiation
* Phosphorescent pigments aren't radioactive so are much safer to use
