Answers. Unit 2 Nature s chemistry. Chapter 8 Fuels and energy 1: Fuels. Activity 8.1. Activity 8.2. Activity 8.3

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1 NATURE S EMISTRY Answers Unit 2 Nature s chemistry hapter 8 Fuels and energy 1: Fuels Activity (a) Fossil fuels (b) ydrocarbons (c) Oxygen (d) arbon dioxide (e) Use p paper to test the p of droplets condensing on the test tube; the p should be 7. Use cobalt chloride paper which will turn from blue to pink in the presence of water. Activity (a) burned (b) energy (c) rude (d) coal (e) fossil (f) fuels (g) carbon (h) water (i) vegetable (j) proteins 2. (a) Oxygen (b) (i) To cool the tube and condense water vapour (ii) The limewater will turn milky. (c) food + oxygen carbon dioxide + water 3. All the foods produced carbon dioxide and water. 4. You should find that foods with a high fat/oil content burn well and give the most energy. The table below gives the actual energy released by 100 g of the foods you might have tested. Food tested Energy (kilojoules per 100 g) peanut 2370 potato crisps 2170 biscuit (digestive) 2014 sugar 1620 bread 1110 Activity (a) Alcohol molecules are not hydrocarbons because they also contain oxygen atoms. (b) alcohol + oxygen carbon dioxide + water 20

2 FUELS AND ENERGY 2: ONTROLLING FIRES hapter 9 Fuels and energy 2: ontrolling fires Activity (a) Fuel, oxygen and heat (b) The fire triangle Activity (a) (i) On burning solids such as wood, paper, cloth (ii) eat (b) Dry powder and carbon dioxide (c) Foam and carbon dioxide 2. Oxygen 3. Using foam (i) removes heat, cooling the fire, and (ii) prevents oxygen getting to the fire. 4. Putting a fire blanket or towel soaked in water over a burning chip pan. This stops oxygen getting to the burning oil. Also switch off heat source. 5. Using water or a foam that contains water on an electrical fire can lead to electrocution as water can conduct electricity. 6. Ask your teacher to give feedback on your leaflet. Activity The carbon dioxide acts like a blanket and stops oxygen in the air getting to the burning candle. 2. (a) arbon dioxide (b) The foam from the extinguisher stops oxygen getting to the tea light. 21

3 NATURE S EMISTRY hapter 10 Fuels 1: Fossil fuels Activity (a) hlorophyll (b) Oxygen (c) The energy is stored in bonds holding the atoms in sugar and starch compounds together. Activity A fossil fuel is a fuel that has been formed from the decaying remains of ancient plants and animals. 2. (a) Some of the things the same are: coal and oil were formed millions of years ago they were formed from living things that had died and were decaying they were covered over by mud and sand which squashed them and buried them deeper heat from within the Earth helped change the decaying plants and animals into coal and oil. (b) Things that were different are: coal was made from plant material such as trees oil was made from tiny sea creatures oil is trapped below impermeable rock. 3. Your flow charts will not look exactly like these but should describe the same stages. (a) Formation of coal energy from Sun helps plants to grow 300 million years ago, dead plants and trees fall into swampy water dead plants and trees are covered by mud, which stops them from decaying combination of layers of mud and heat from underground rocks causes plant remains to be squashed after millions of years of heat and pressure, the remains of the dead plants turn into coal 22

4 FUELS 1: FOSSIL FUELS (b) Formation of oil and natural gas energy from Sun helps microscopic sea creatures to grow, and be consumed by sea creatures millions of years ago, the sea creatures died and were covered by mud and sand, which stops them from decaying combination of layers of mud and heat from underground rocks causes remains of sea creatures to be squashed after millions of years of heat and pressure, the remains of the sea creatures turn into oil and natural gas Activity 10.3 Arguments for fracking include: creates jobs provides a new domestic energy source makes the country less reliant on imports extends the time before supplies run out. Arguments against fracking include: may cause minor earthquakes can pollute water supplies may have impacts on health such as asthma levels in children undermines efforts to tackle climate change. 23

5 NATURE S EMISTRY Activity (a) Supplies of fossil fuels will eventually run out. When they are used up, they cannot be replaced. (b) Fracking and deep-water drilling 2. (a) 35 (billion barrels) (b) 2008 (c) New discoveries of reserves 3. Information likely to be included in your report is: the Deepwater orizon was a drilling rig operated by British Petroleum (BP) in the Gulf of Mexico on 20 April 2010 a leak developed and a blowout preventer which would have sealed the well failed. The flow of oil and gas couldn t be controlled. These caught fire and caused several explosions on the rig. It took 5 months to finally seal the well there was lots of damage to the marine environment with the deaths of many fish, sea turtles and dolphins hundreds of miles of coastline were badly polluted by oil the disaster has cost BP more than $44 billion in fines, compensation and clean-up costs. 4. (a) Gas reserves (trillion cubic feet) Year (b) From 1970 until 1990 gas reserves fell as the amount of gas used was greater than new discoveries. From 1995 until 2015 gas reserves rose as the amount of new gas discoveries was greater than the amount being used. 24

6 FUELS 1: FOSSIL FUELS Activity (a) ydrocarbons (b) arbon dioxide and water (c) (i) arbon and carbon monoxide (ii) Incomplete combustion 2. (a) (i) Oxidation (ii) omplete combustion (b) Exothermic 3. atalytic converters are used to reduce emissions of poisonous carbon monoxide and oxides of nitrogen which causes acid rain. Activity (a) 38 (b) 3 (c) 4 (d) 5 (3O2 have 6 oxygen atoms, 42O have 4 oxygen atoms, giving a total of 10 oxygen atoms; dividing by 2 gives 5 molecules of oxygen, O2) (e) + propane + oxygen carbon + carbon dioxide hydrogen + water oxygen The number of each type of atom is the same on both sides of the equation. No mass has been gained or lost. Therefore this demonstrates the law of conservation of mass S1-N4 hemistry SB_Unit 2_Answers.indd 25 12/08/17 11:23 AM

7 NATURE S EMISTRY hapter 11 Fuels and energy 3: The problems with using fossil fuels Activity (a) A mixture of smoke and fog which is dangerous to health (b) Reduce use of coal; close coal-fired power stations; shut polluting factories; phase out polluting vehicles (c) To stop breathing in fine soot particles that are given out by car exhausts (d) Breathing problems and heart problems 2. Answers will vary but ideas for your poster could include: a graphic of a cyclist with a mask, statistics on death rates due to air pollution and different types of air pollution or a before cartoon of one cyclist with a mask and one without, and an after cartoon with one looking happy and one coughing and wheezing, with a caption wear a mask. 1. Activity Individual/household emissions ousing Transport Food onsumption Other Emissions (%) Theme (a) Methods include: insulating, draught proofing and double glazing, turning down the heating and hot-water thermostats, reducing the time the heating is on, using energyefficient heating systems and microgeneration technologies. (b) Using energy-efficient light bulbs and appliances; washing clothes at a lower temperature (c) Walking; cycling; using car share; using public transport (d) Sustainable: able to be done in a way that meets present needs without making it difficult for future generations to meet their needs because we have used up the resources. Seasonal: available according to local growing conditions (not imported). Eating a sustainable and healthy diet will reduce greenhouse gas emissions because food isn t grown out of season in heated greenhouses or transported from other countries, both of which use energy.

8 FUELS AND ENERGY 4: MEETING ENERGY NEEDS IN TE FUTURE 3. (a) Greenhouse gases (b) Using electric power packs instead of diesel engines to power the buses (c) 18% (d) (i) 50% (half) of all buses to be low emission by 2032 (ii) Because the graph is nearly a straight line which is steadily increasing, it is hoped that this will increase steadily from 2017 to 2032, by replacing diesel buses with low-emission vehicles hapter 12 Fuels and energy 4: Meeting energy needs in the future Activity Biomass 2. Biodiesel; bioethanol; biogas (biomethane) 3. They release the same amount of carbon dioxide into the atmosphere when they burn as was absorbed by the plants that produced them. 4. (a) Sugarcane and sugar beet (b) Biodiesel (c) Biomethane 5. (a) Type of climate Yield Sugar content (%) required (tonnes per hectare) Sugarcane tropical Sugar beet temperate (b) (i) It was too labour intensive, making it uneconomic. (ii) Bioethanol Biofuel Number of plants Total capacity (million litres) Feedstocks biodiesel used cooking oils; waste oils; tallow; sewage grease bioethanol wheat; sugar beet biomethane 1 5 municipal (town) solid waste 27

9 NATURE S EMISTRY Activity Scotland relies on a mix of energy sources. These include nuclear, hydroelectric, wind, and wave and tidal energy. Peterhead power station is the only power station that still uses fossil fuels. 2. (a) (i) Finite (ii) Renewable (iii) Nuclear (b) Solar (c) Biomass (d) Geothermal 3. Any two from: buses powered by hydrogen fuel cells only emit water/don t emit carbon dioxide; don t cause air pollution; are quieter and smoother running. 4. (a) Scotland has mountains and fast-flowing rivers. (b) During periods of low electricity demand, excess electricity is used to pump water from the loch into a dam high above the power station. At periods of high electricity demand, the water from the dam is allowed to flow down through the turbines, generating electricity. Activity (a) (i) An energy source whose present-day use does not affect future use. (ii) Sustainable energy sources reduce greenhouse gas emissions. (b) Any two from: risk of accidents; high cost of construction; high decommissioning costs; difficulty of dealing with radioactive waste. (c) ydroelectric power stations can be switched on and off quickly. (d) Tides are predictable, whereas wind and solar are not. 2. Answers may vary but should include an overview of the potential energy sources that could be used to meet Scotland s future energy needs and your own ideas about which are most suitable. hapter 13 Fuels 2: Solutions to fossil fuel problems Activity (a) (i) Respiration (ii) Photosynthesis (iii) Respiration (b) Burning fossil fuels is increasing the concentration of carbon dioxide in the atmosphere. 28

10 FUELS 2: SOLUTIONS TO FOSSIL FUEL PROBLEMS Activity Planting forests and regenerating peat bogs 2. Growing trees absorb carbon dioxide from the atmosphere. 3. A lack of oxygen in the water slows the decay process. Activity Step 1: Remove the carbon dioxide from the gases being emitted to the atmosphere Step 2: ompress the gas Step 3: Inject the carbon dioxide into suitable rocks deep in the Earth s crust Activity Biofuels only release the carbon dioxide that the plants used to make the biofuel, absorbed from the atmosphere during their growing cycle. Activity Report Answers will vary but should include conclusions about which type of biomass produces biogas most quickly and which type produces most biogas. The results depend on what you used. The mixture of cow manure + other biomass material, such as vegetable peelings, should produce much more biogas than the cow manure on its own. Your graph will look similar to the one shown, but details will vary depending on the actual cow dung + biomass conditions. The rate at which cow dung produces biogas is faster at the start than the cow dung + biomass mixture. 40 g of cow dung can produce about 800 cm 3 cow dung of biogas. Also state any two ways of making your experiment fair from: the same mass of biomass was used in each case the bottles were filled to the same level with distilled water the bottles were kept in the same conditions Biogas may be given off at different rates when Time (days) different types of biomass are heated. ircumference of balloon (cm) 29

11 NATURE S EMISTRY Activity The mass (weight) of seeds or nuts used must be the same in each case. 3. Biomass is material that can be obtained from living things and burned to produce energy. Three biofuels that can be obtained from biomass are biogas from decomposing waste, bioethanol made by fermenting sugar, and biodiesel that can be made from used cooking oil. Purified biogas that is suitable for injecting into the national gas grid is known as liquid biomethane. Activity Wind farms and solar panel sites. 2. Risk of injury to birds, bats and marine life 3. Decaying plants can release greenhouse gases 4. Release of hydrogen sulfide, which smells, and release of trapped greenhouse gases Activity Wind turbines 2. (a) 0.7 arbon dioxide emissions (kg of O 2 per kilowatt hour of electricity produced) Natural gas oal Solar cells Wind turbine Geothermal Wave/Tidal ydroelectricity Power generation source (b) Using sustainable energy sources instead of fossil fuels means that less carbon dioxide will be released into the atmosphere. This will slow the rise in (stabilise/decrease) the concentration of O 2 in the atmosphere. 30

12 FUELS 3: YDROARBONS hapter 14 Fuels 3: ydrocarbons Activity (a) Fractional distillation (b) Molecules made up of only carbon and hydrogen atoms. (c) Fractions 2. (a) Fraction A (b) Fraction B (c) Fraction A (d) Fraction A 3. (a) Gasoline (b) Gasoline (c) (i) Petrol (ii) Diesel (d) Paraffin or aircraft fuel Activity (a) A formula that shows the number of atoms of each type that are in the molecule (b) A formula that shows how the atoms are joined together in a molecule 2. (a) You should be able to build models of the alkanes named in the table. (b) See column 3 of the table below. (c) Alkane name Number of carbons Number of hydrogens Molecular formula Full structural formula methane ethane propane (continued) 31

13 32 Activity (a) pentene hexene heptene octene propene butene ethene NATURE S EMISTRY butane pentane hexane heptane octane (d) Pent- indicates the number of carbons (five); -ane indicates it is an alkane with single carbon-to-carbon bonds. (e) It can form four bonds, so it can bond to itself to form long chains, and also to other atoms.

14 33 FUELS 3: YDROARBONS (b) 2. There are always twice as many hydrogens as carbons in the molecules. 3. (a) Alkenes (b) It indicates that the molecules of the compound contain a carbon-to-carbon double bond. 4. Add bromine solution to samples of each and shake. The alkene will decolourise the bromine solution immediately, but the alkane will not. Alkene name Number of carbons Number of hydrogens Molecular formula Full structural formula propene pentene hexene heptene octene Activity (c) (d)

15 NATURE S EMISTRY 2. (a) 7 16 (b) (i) + (ii) There is not a great demand for heavy fractions. racking breaks the large molecules in unwanted heavy fractions into smaller, more useful molecules. 4. (a) atalytic cracking (b) (i) 3 6 (ii) Octane; ethene; propene 5. (a) (i) The alkane molecules in liquid paraffin are very large. (ii) The bromine solution will not be decolourised. (b) (i) The gas consists of hydrocarbons. (ii) Because the product is a gas, the molecules must be small. Because the bromine solution is decolourised immediately, the molecules must be alkene molecules. (c) The delivery tube must be removed from the water to prevent suck-back. hapter 15 Everyday consumer products 1: Plants for food Activity Food arbohydrate Sugars Starch Fats and oils Protein bread Brazil nut apple breakfast cereal pasta 34

16 EVERYDAY ONSUMER PRODUTS 1: PLANTS FOR FOOD Activity Plants are a vital source of nutrients. The foods we obtain from plants include proteins, carbohydrates, fats and oils, vitamins and minerals. 2. Starch and sugars 3. Proteins 4. Starch and sugar 5. Protein 6. arbohydrates: provide the body with energy. Proteins: needed for growth and repair of body tissue. Fats and oils: provide the body with energy and act as an insulator against cold. Vitamins: needed for normal growth, to repair tissue, to fight infection and to prevent diseases. Minerals and trace elements: for example, calcium is needed for healthy bones and teeth, iron is needed for healthy blood. Activity (a) Obesity (b) arbohydrates, and fats and oils. (c) (i) 28 (kg/m 2 ) (ii) overweight 2. Their diet does not contain enough vitamins and minerals. Scurvy is caused by a lack of vitamin in the diet. Rickets is caused by a lack of vitamin D. 3. Essential fatty acids 4. Any one from: lower body weight; lower blood pressure; reduced cholesterol; reduced risk of heart disease, stroke and cancers. 5. Disease/condition Vitamin/mineral deficiency Plant source of vitamin/mineral scurvy vitamin red pepper, curly kale, kiwi fruit rickets vitamin D no significant plant source anaemia iron (Fe) spinach, oatmeal, sunflower seeds and soya beans beriberi vitamin B1 spinach and sunflower seeds pellagra vitamin B3 oatmeal 35

17 NATURE S EMISTRY Activity (a) Sugars (carbohydrates) (b) Fermentation (c) The wine could be distilled. The wine would be heated producing vapours with a high alcohol content. These would be condensed and collected, producing brandy. 2. (a) 5.6 units ( ) (b) A bottle of strong beer and a whisky (3 units) would have less alcohol than two glasses of wine (at least 4 units). (c) Ensuring labels on alcoholic drinks show units of alcohol and recommending maximum and low-risk levels of drinking for men and women Activity In your experiment you should observe: yellowing of leaves for mung beans grown in culture medium lacking nitrogen stunted growth for mung beans grown in culture medium lacking potassium poor root development for mung beans grown in culture medium lacking phosphorus. 2. In your experiment you should observe that fertiliser improves the development of roots and leaves. Activity hemical symbol Element hemical symbol Element N nitrogen Mn manganese P phosphorus Fe iron K potassium Zn zinc S sulfur u copper a calcium Mo molybdenum Mg magnesium carbon B boron hydrogen l chlorine O oxygen 36

18 EVERYDAY ONSUMER PRODUTS 2: OSMETI PRODUTS 2. (a) Nitrogen, phosphorus and potassium (b) (i) To increase the yield of crops for food, or for other purposes such as making alcohol (ii) Growing crops absorb nutrients from the soil. ropping removes the nutrients. Fertilisers are used to replace the nutrients. hapter 16 Everyday consumer products 2: osmetic products Activity (a) cosmetics (b) carbohydrates (c) Fats (d) oils Activity Essential oils are responsible for the distinctive aroma of plants and can be extracted by steam distillation. 2. Lavender has calming effects on the body. 3. Spearmint and peppermint 4. As muscle pain relief 5. They might feel energised. 6. Any of the oils that have memory-boosting capacity (basil, cypress, lemon, peppermint, rosemary) 7. You should be able to detect a very small quantity of essential oil by visual inspection or by smell. Activity (d) Over the period of time, the strength of the smell should decrease gradually from strong to very faint. (e) (i) A simple Eau de ologne-type fragrance can be made by dissolving a few drops of essential oil in a water and alcohol mixture. (ii) Molecules of the essential oils evaporate from the skin. When there are fewer essential oil molecules on the skin, the scent will only be detected faintly. 2. You may be able to detect a range of different essential oils, distinguishing between them by smell. 37

19 NATURE S EMISTRY 3. Answers will vary but should consist of a list of essential oils and the products that contain them. 4. (a) 41.6% ( ) (b) 2.25 billion 5. (a) Steam distillation (b) The liquid that was distilled would have a scent of rosemary and there may be evidence of a small amount of oil on the surface of the water in the flask. (c) Roots: ginger; flowers: lavender; peel: orange; wood: sandalwood; stem (and leaves): peppermint 6. (a) Orange (b) Floral (c) (i) Patchouli and vetiver are classed as base notes because their scents last a long time on the skin/take a long time to evaporate from the skin. (ii) A woody scent (d) The perfume has all three types of notes and can, therefore, be described as balanced. hapter 17 Everyday consumer products 3: Plants for energy Activity arbohydrates and oils can be burned. 1. B Activity (a) 6 12 O 6 (b) (i) It is made of many glucose molecules joined together in a long chain. (ii) Because it is made of many glucose molecules (compared with simple carbohydrates such as glucose, fructose, maltose and sucrose). 3. (a) When glucose is heated with Benedict s solution the blue solution turns brick-red. (b) Starch gives a blue black colour with iodine solution. Activity When iodine is added to a sample of the water surrounding the visking tubing containing the starch it doesn t give a blue black colour. The starch molecules are too large to pass through the visking tubing into the water. When the water surrounding the visking tubing containing the glucose solution is tested with Benedict s solution, a brick-red colour is produced. Glucose molecules are small enough to pass through the visking tubing into the water. 38

20 EVERYDAY ONSUMER PRODUTS 3: PLANTS FOR ENERGY Activity (a) Starch gives a blue black colour with iodine. (b) Amylase is an enzyme. (c) eat a sample of the solution with Benedict s solution. A brick-red colour is produced in the presence of glucose. 2. (a) As time passes, there is less starch present, because the starch is being broken down by the amylase. (b) Benedict s solution gives a brick-red colour because starch has been broken down to produce glucose. Activity Answers will vary but should contain reference to the froth on the top of the liquid, which shows that a gas is being produced, and that limewater turns milky because carbon dioxide is produced. Activity (a) The enzymes stop working because the yeast cells die when the alcohol percentage becomes too high. (b) Spirits have a much higher alcohol content than the percentage alcohol at which yeast enzymes will work, so spirits cannot be produced by fermentation alone. Distillation is needed to increase the percentage alcohol content. 2. Answers will vary but should cover these facts: Barley is malted to produce sugars. Enzymes in the barley break starch down to simple sugars. The malted barley is then allowed to ferment. Enzymes break the sugars down, producing alcohol (ethanol). The percentage of alcohol is increased by distillation. The distilled spirit is allowed to mature in wooden barrels to produce whisky. 3. Any two from: cider (from apples), rum (from sugarcane) and vodka (from potatoes). 4. (a) Volume of alcohol = = 280 cm Units of alcohol = 280 = 28 units 10 (b) Volume of alcohol = units 10 = = 16 cm 3 39

21 NATURE S EMISTRY Activity (a) Biological catalysts (b) arbon dioxide (c) (i) p of 8 ( ) (ii) Temperature 2. You should find that amylase works well at temperatures around 40 and at p 7 (neutral). hapter 18 Plants to products Activity You will be able to dye fabrics with vegetable colours. You should find that using a mordant improves the dyeing process and that the p of the dye solution can influence colour. 2. (a) Indigo (b) The roots (c) Mordant Activity (a) Morphine or codeine (b) eroin or opium (c) Any one from: can be addictive; can cause harm to users; can cause harm to society. Activity (a) Active compound (b) To improve the taste and appearance of a medicine or to improve the shelf-life of a medicine. 2. (a) (i) 2.5 ml (cm 3 ) (ii) To ensure that a fever due to serious infection can be diagnosed quickly (b) 4 3. Answers may vary but should include information from various medicine packaging, showing what the medicines contain, how they should be stored, what they can be used for and how they should be used. 40

22 UNIT 2 PRATIE ASSESSMENT Unit 2 practice assessment National 3 1. (a) Fuels 1 (b) A compound made of only hydrogen and carbon atoms 1 (c) (i) Water 1 (ii) Limewater turns milky/cloudy 1 2. (a) Fuel, oxygen and heat 1 (b) Risk of electrocution 1 3. (a) Fossil fuels are a finite resource or Using sustainable sources reduces greenhouse gas/carbon dioxide emissions. 1 (b) When demand for electricity is low, surplus electricity from other sources is used to pump water into a reservoir higher in the hills 1 and At times of high electricity demand, water is released from the reservoir and used to produce electricity. 1 (c) Low/no generation of electricity when wind speed is very low. 1 (d) Wood or crop waste, etc 1 (e) Sugar beet could be processed to give biofuels/bioethanol (a) They replace the nutrients that plants need which cropping removes from the soil. 1 (b) arbohydrates provide the body with energy. 1 (c) Fermentation 1 (d) million tonnes 1 5. (a) Steam distillation 1 (b) Smell of essential oil or essential oil floating on top of the water 1 (c) Spearmint or peppermint 1 (d) Base note 1 6. (a) The plant material should be chopped finely or crushed 1 and The plant material should be heated in water or other solvent. 1 (b) Dyeing fabrics or as a food colouring 1 7. Willow or meadowsweet 1 Total 24 41

23 NATURE S EMISTRY National 4 1. rude oil is formed from the decaying remains of small sea creatures 1 and Over a long period of time, temperature and pressure change the remains into crude oil (a) ombustion or oxidation 1 (b) Exothermic 1 (c) Any from: carbon monoxide, carbon (soot). 1 (d) arbon dioxide produced by burning the fossil fuels is separated from the gases released to the atmosphere 1 and The carbon dioxide (is liquefied and) stored in rock formations Foam from the extinguisher cuts off the supply of oxygen to the burning fuel (a) MW 1 (b) Any from: biogas, biomethane, (bio)ethanol, biodiesel (a) The hydrocarbons in each fraction have similar boiling points. 1 (b) 1 (c) (i) (ii) or Both of these are acceptable structural formulae; the formula showing bonds is termed a full structural formula, and the other is described as a shortened structural formula. 6. (a) Alkanes 1 (b) racking produces unsaturated compounds or racking produces alkenes or racking produces molecules containing double bonds. 1 (c) (a) Iodine solution will produce a blue black colour. 1 (b) Enzymes are biological catalysts. 1 (c) The formula contains, and O and the : ratio is 2 : 1 1 (d) 28 ± 1 1 (e) Distillation 1 8. (a) As time passes the rate at which caffeine is extracted from the tea bag decreases. 1 (b) 225 mg 1 9. (a) Active ingredient 1 (b) Morphine or heroin 1 1 Total 26 42