C1 – Carbon Chemistry

1. C1 – Carbon Chemistry Revision Lesson Two

2. Ethene This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION Monomers and Polymers Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics… Step 1: Break the double bond Step 2: Add the molecules together:

3. H H H H C C C C H H H H Ethene Ethene Poly(e)thene H H H H C C C C H H H H n C C n C C C C CH3 CH3 H H e.g. n C C n H H H H Another way of drawing it… Instead of circles, let’s use letters… General formula for addition polymerisation:

4. H H H H n C C n H H H H H H H H n C C n H H Cl Cl Cl Cl H H C C C C C C n C C n H H Br Br Some examples

5. Properties of plastics • Strong covalent bonds hold atoms together in polymer chains. Forces determine properties • Weak intermolecular forces – slide over one another – plastic can be stretched easily/low melting point • Strong intermolecular forces/covalent bonds (cross-linking bridges) – rigid/high melting points

6. Uses of addition polymers Poly(ethene) Poly(propene) Poly(styrene) Poly(chloroethene), PVC Packaging – foam = thermal insulator

7. Man made fibres Nylon – lightweight, tough, waterproof, blocks UV Gore-tex – nylon coated with PTFE – this means that it can allow perspiration to escape but rain cannot get in (it can “breathe”)

8. 1) Landfill sites - most plastics do not _________ which means that landfill sites are quickly filled up. Research is being carried out on __________ plastics. 2) Burning – this releases carbon dioxide which causes the ________ effect, as well as other ________ gases. 3) _______ – the best option, but difficult because of the different types of plastic Disposal of plastics Words – recycling, greenhouse, decompose, biodegradable, poisonous

9. Questions on Polymers Complete the table by filling in the names of the missing monomers and polymers (2) What reaction conditions are used to convert monomers into polymers? (1) Give one environmental problem associated with the disposal of plastics (1) Describe a chemical test to distinguish between ethene and polyethene. (2)

10. Questions on Polymers Complete the table by filling in the names of the missing monomers and polymers (2) What reaction conditions are used to convert monomers into polymers? (1) High pressure and catalyst Give one environmental problem associated with the disposal of plastics (1) Non biodegradable/ burning gives off fumes

11. Although these fuels look different, they all contain CARBON and HYDROGEN – they’re called HYDROCARBONS Fuels A “fuel” is something that can be burned to release heat and light energy. The main examples are:

12. Does it create pollution? Availability How much energy does it release? Is it toxic? How much does it cost? Is it easy to use, store and transport? Choosing a fuel Which fuel should you use?

13. H H H O O O O O O O O O O O O H H + Oxygen Carbon dioxide + Water C C C C H H H H H H Carbon monoxide H H H H H Methane + Oxygen + Water Burning Fuels Lots of oxygen: Methane CH4 + 2O2  CO2 + 2H2O COMPLETE COMBUSTION – LOTS OF ENERGY Little oxygen: Carbon 4CH4 + 6O2  C + 2CO + CO2 + 8H2O INCOMPLETE COMBUSTION – little energy

14. O Carbon dioxide is a _______ gas and helps cause global _______. C O Carbon monoxide combines with ___________ in the _____ and reduces the ability for red blood cells to carry _______. O C Words – haemoglobin, warming, oxygen, greenhouse, blood Pollutants from burning fuels

15. Fuels Questions • (a) Apart from water, name two other products formed when an alcohol fuel burns. (2) • (b) The fuel in question (a) was ethanol. Write a word equation for the complete combustion of ethanol. (1) • (c) Under what conditions does incomplete combustion occur? (1) • (d) Why is it necessary to regularly service gas appliances? • (a) carbon dioxide and energy • (b) ethanol + oxygen = carbon dioxide + water • (c) Less oxygen • (d) Faulty fires give off the poisonous gas carbon monoxide a clue for this is black soot - carbon

16. “specific heat capacity” Energy from fuels Specific heat capacity tells you how mush energy something can store Step 1: Calculate the energy gained by the water: Energy gained by water = mass of water x 4200 J/kgC0 x change in temperature How much energy is needed to heat 2 kg of water from 10oC – 100oC? 2 x 4200 x 90 = 756 000 J

17. Paint Paint is a mixture of different materials: • A pigment – a finely powdered ______ that has a strong ______ • A binding medium – an oil that sticks the _______ to the surface • A solvent – dissolves the binding medium and makes the surface easier to _____ When paint dries the solvent ______ away. In emulsions the solvent is water whereas in gloss paint the solvent is ____. Words – oil, coat, solid, colour, pigment, evaporates

18. Special Pigments Thermochromic pigments Phosphorescent pigments Glow in the dark – absorb natural light and store energy – released over time Eg watches/traffic signs/novelty decorations Change colour when heated Eg. Bath toys/baby spoons – safety Hi

19. Exam Questions Standard Demand 1.) Using paint as an example, describe what a colloid is? (2 marks) 2.) A paint is often used to decorate or protect a surface. Finish the sentence to explain why. Choose the best words from the list. solvent surface applied When a paint is _______ as a thin _______ when it dries the _______ evaporates (3 marks) 3.) What makes oil paints dry? (1 mark) 4) Name two differences between water based and oil based paints (2 marks)

20. Exam Questions High Demand 5.) Phosphorescent paints are used in watches so that cave divers can tell the time in the dark. Explain why this makes them safer than radioactive substances (2 marks) • Colloid consists of tiny particles of pigment (usually a solid) are dispersed through a liquid • When a paint is applied as a thin surface when it dries the solvent evaporates • Binding medium is oil, solvent is an organic compound. First the solvent evaporates, then oil is oxidised by oxygen in the air and it solidifies. • Emulsion – fast drying and don’t produce fumes, used to paint inside walls (not waterproof) • Radioactive paints used to be used because they would glow for years. Phosphorescent paints are much safer, and don’t give off radiation

21. What’s in Air? • The air is a mixture of different gases. • It is rarely clean around big cities, but clean air has no pollutants caused by human activity. • The main gases in clear air are: • Varying amounts of water vapour • The noble gases are a group of unreactive elements: argon, neon, krypton and xenon NITROGEN – 78% OXYGEN – 21% ARGON – 0.9% CARBON DIOXIDE – 0.035%

22. The Levels of Atmospheric Gases Combustion of Fossil Fuels This increases the level of CO2 and decreases the level of O2 (think back to the equation for combustion) • The levels of gases in the air depends on: Respiration by Animals & Plants Again, this increases the level of CO2 and decreases the level of O2 Photosynthesis by Plants This decreases the level of CO2 and increases the level of O2 (this is good!)

23. Copy this diagram into your books... Title: Carbon Cycle Oxygen and Carbon Dioxide in the Air Respiration Uses up oxygen, gives out carbon dioxide Respiration Uses up oxygen, gives out carbon dioxide Combustion Uses up oxygen, makes carbon dioxide Photosynthesis Uses up carbon dioxide, makes oxygen FUELS PLANTS ANIMALS f e e d i n g

24. Higher -Evolution of the Earth’s Atmosphere In Earth’s early history, gases such as CO2 have been escaping into the atmosphere. • Scientists can only speculate about the original atmosphere of the Earth, but quite a lot is now known. At some point, microbes developed that could photosynthesise... Eventually, the level of oxygen reached what it is today.

25. Atmospheric Pollutants • The atmosphere contains a large number of pollutants. • Copy the table below, which shows the main ones: • You can see that acid rainis produced by both oxides of nitrogenand sulphur dioxide.

26. More on Catalytic Converters • Exhaust gases contain pollutants such as nitric oxideand carbon monoxide. • A catalytic converter converts: • Although carbon dioxide is a greenhouse gas, it is much less harmful to health than carbon monoxide. • Nitric oxide causes photochemical smog, so its conversion to nitrogen is good for the environment. Carbon Monoxide into... Carbon Dioxide! Nitric Oxide into... Nitrogen! Cough...

27. Catalytic Converters: Higher Remember that nitrogen monoxide contributes to acid rain and smog • The 78% of the atmosphere that is nitrogen, is highly unreactive. • However, the high temperaturesinside a combustion engine allow nitrogen to react with oxygen, forming the oxides of nitrogenthat we have learnt about. • A catalytic converter contains a rhodium catalyst, which causes the following reaction: O O N N Nitrogen Monoxide Oxygen (O2) Nitrogen (N2) carbon monoxide + nitrogen monoxide  nitrogen + carbon dioxide 2CO + 2NO  N2 + CO2

28. Key ideas Incomplete combustion in car engines produces ____________ monoxide gas, which is poisonous. It also produces oxides of __________. These gases cause ______rain and photochemical _______. To cut traffic pollution, car exhausts can be fitted with __________ converters which remove carbon __________. Words to use: nitrogencarbon smog monoxideacidcatalytic

29. Exam Questions Standard Demand 1.) What percentage of oxygen and nitrogen is there in the air? (2 marks) 2.) The composition of carbon dioxide in the air remains constant. Complete the following: 0.04% photosynthesis respiration The amount of carbon dioxide in the air is approximately ____. Plants use carbon dioxide during __________ and give out carbon dioxide during the process of _______________ (3 marks)

30. Exam Questions High Demand 3.) Explain how human activity has contributed to increasing levels of carbon dioxide. (2 marks) • 78% nitrogen and 21% oxygen • The amount of carbon dioxide in the air is approximately 0.04%. Plants use carbon dioxide during photosynthesis and give out carbon dioxide during the process of respiration • Human population is increasing therefore more people respiring, energy demands are increasing (burning fossil fuels-gives off carbon dioxide), and more deforestation to make room for houses and growth of food.

31. 6 mark question • The quality of written communication will be assessed in your answer to this question. • Explain how a catalytic converter helps to reduce pollution.

32. Level 3 Answer correctly applies knowledge of how catalytic converters changes carbon monoxide into carbon dioxide and oxides of nitrogen into nitrogen. Understanding shown of how these are less polluting than the others, describing how carbon monoxide and oxides of nitrogen can cause atmospheric pollution. All information in answer is relevant, clear, organised and presented in a structured and coherent format. Specialist terms are used appropriately. Few, if any, errors in grammar, punctuation and spelling. (5–6 marks) Level 2 Answer applies knowledge of how catalytic converters work and why they are important. For the most part the information is relevant and presented in a structured and coherent format. Specialist terms are used for the most part appropriately. There are occasional errors in grammar, punctuation and spelling. (3–4 marks) Level 1 An incomplete answer, states that catalytic converters reduce atmospheric pollution. Answer may be simplistic. There may be limited use of specialist terms. Errors of grammar, punctuation and spelling prevent communication of the science. (1–2 marks) Level 0 Insufficient or irrelevant science. Answer not worthy of credit. (0 marks)