LEVEL 1/2 SCIENCE FOR WORK

Transcription

1 Candidate Name Centre Number Candidate Number LEVEL 1/2 SCIENCE FOR WORK SPECIMEN EXTERNAL ASSESSMENT AM/PM xxxday xx June 20** Unit 1: Reducing Our Carbon Footprint (1 hour) For Examiner s use only Question Maximum Mark Mark Awarded Instructions to candidates Total 54 Answer all questions. Write your answers in the spaces provided in this booklet. Information for candidates The total mark for the paper is 54 marks. You are reminded of the necessity of good English and orderly presentation of your answers. The number of marks is given in brackets at the end of each question or part question. You will need a calculator and ruler for this exam. A list of equations is printed on page 12 of the examination paper. You should show your workings to calculations.

2 Answer all the questions in the spaces provided. 1. Carbon dioxide is recycled constantly through various processes that form the carbon cycle. (a) Look at the processes in the following table and place a tick in the correct column to show if it releases or absorbs carbon dioxide. [3] Process Photosynthesis Plant respiration Burning of fossil fuels Tick( ) if CO 2 is released Tick( ) if CO 2 is absorbed (b) Give two reasons why deforestation increases the amount of carbon dioxide in the atmosphere. [2] (c) Energy produced using wind turbines typically has a carbon footprint of approximately 5 g/kwh compared to 802 g/kwh for oil. Explain why wind turbines have a low carbon footprint. [3]

3 2. Methane is a gas produced when cows belch. Methane is a greenhouse gas. The carbon dioxide equivalent of methane is 21. (a) Identify the correct statement by placing a tick ( ) in the correct box. [1] (i) Carbon dioxide equivalent allows us to compare the effect of methane and carbon dioxide on atmospheric pressure. (ii) Carbon dioxide equivalent allows us to compare the effect of methane and carbon dioxide on global warming. (iii) Carbon dioxide equivalent allows us to compare the effect of methane and carbon dioxide on the ozone layer. Tick ( ) (b) In 1980, Australian dairy cows weighed about 500 kg and produced about litres of milk each year. The amount of methane produced was equivalent to 693 g CO 2 for each litre of milk produced. In 2010, Australian dairy cows weighed about 600 kg and produced about litres of milk each year. The amount of methane produced was 24 g of methane for each litre of milk produced. Calculate the carbon dioxide equivalent for each litre of milk produced in 2010 and comment on the effect of these changes on the carbon footprint of milk production. Show your workings. [3]. 2

4 3. The following article is about carbon emissions from the production of food in the UK. A recent study has shown that each person in the UK has an annual carbon footprint of 11 tonnes of CO 2. About 20% of the average personal carbon footprint comes from the food we eat. If we understand how our food choices contribute to our carbon footprint, we will be in a position to reduce our daily personal carbon emissions. This will also help the UK to meet its aim to reduce carbon emissions by The diagram below shows the different contributions to the carbon footprint for the production of the food we eat. Contributions to carbon emissions Rotting food and packaging 13% Other 6% Transport 15% Food processing and packaging 21% Fertiliser use 30% Methane from cattle 15% (a) State what is meant by the term carbon footprint. [2] 3

5 (b) The article states that each person has an annual carbon footprint of 11 tonnes and about 20% of this comes from the food we eat. Use this information to find the carbon footprint for a person, due to the food they eat. (Show your workings.) [2] (c) Use the chart in the article to help answer the following questions.. tonnes CO 2 (i) Which factor contributes most to carbon dioxide emissions in food production? [1].. (ii) Llinos wishes to reduce her carbon footprint due to the food she eats. Suggest three ways she can do this. [3]

6 4.(a) George wishes to reduce the carbon footprint of his home. Look at the following list and select one action he can take to do this. [1] Charge mobile phone overnight on lower cost tariff (cheaper electricity) Install air conditioning Install cavity wall insulation Increase the temperature setting on the thermostat for the central heating Action.. (b) The information below is taken from George s satellite box. Mains AC V Hz Power consumption ON 45 W Stand-by 30 W The following conversion factor is taken from a government website. Fuel Quantity consumed Mass CO 2 produced Grid electricity 1 kwh kg (i) State the relationship between power and the energy transferred by George s satellite box. [1]... 5

7 (ii) On average George uses his satellite box for 3 hours a day to watch television. (1) Show that the satellite box uses a total of kwh of electricity each day if George puts the satellite box on standby for the remaining 21 hours. You must show your workings. [2] (2) If George leaves the satellite box on all day rather than switching it to standby, he will use kwh of electricity each day. Calculate how much unnecessary CO 2 George will produce each year by not switching his satellite box to stand-by. You must show your workings. [4] 6

8 5. Manufacturers are concerned to reduce the environmental impact made by using cars. (a) You will compare two different diesel engines. Engine 1 Total energy used: kj Useful energy obtained: kj Engine 2 (i) Balance the equation for the combustion of the main part of diesel, which is hexadecane (C 16 H 34 ). Add numbers to the equation below to balance it. [2] 2C 16 H O 2 CO 2 + H 2 O 7

9 (ii) Determine which car engine makes a more efficient use of fuel. You answer must be supported by worked calculations showing the percentage efficiency of each engine. [6] 8

10 (iii) It has been suggested that petrol engines may have a lower carbon footprint than diesel engines. Explain whether this is supported by the following data. [3] Fuel CO 2 emissions per litre fuel (kg/l) Fuel consumption kilometres travelled per litre fuel (km/l) Petrol Diesel (b) Not all energy obtained from a fuel is used to move a vehicle. Apart from the engine losing energy as heat energy, describe three ways in which energy is lost in driving a vehicle. [3] 9

11 6. Water vapour and carbon dioxide are greenhouse gases. Water vapour contributes to 70% of the greenhouse effect. The greenhouse effect can be split into the natural greenhouse effect and enhanced greenhouse effect. (a) (i) Explain how gases such as carbon dioxide cause the greenhouse effect. [4] (ii) Explain why the natural greenhouse effect is important for life. [2] (b) The enhanced greenhouse effect is linked to increased carbon dioxide levels in the atmosphere. Discuss the likely climatic and environmental impacts of the enhanced greenhouse effect. [6]... 10

12 Useful Equations Work done or energy = force x distance Power (W) = current (A) x voltage (V) Energy (J) = power (W) x time (s) P = IV E = Pt Units used (kwh) = power (kw) x time (h) Cost = units used x cost each unit Percentage efficiency = useful energy transfer x 100 total energy used kgco2eq = mass of gas(kg) x global warming potential of the gas kgco2eq = m(kg) x GWP Units g carbon dioxide equivalent kg carbon dioxide equivalent kg carbon dioxide equivalent per kilowatt hour gco2eq kgco2eq kgco2eq/kwh SI multipliers Prefix Multiplier Prefix Multiplier p k 10 3 n 10-9 M G 10 9 m 10-3 T

13 WJEC LEVEL 1/2 AWARD SCIENCE FOR WORK SPECIMEN EXTERNAL ASSESSMENT MARK SCHEME 12

14 Question Answer Marks 1 (a) 1 mark each correct answer 3 Process Photosynthesis Plant respiration Burning of fossil fuels Tick( ) if CO 2 is released Tick( ) if CO 2 is absorbed (b) 1. Trees can no longer capture CO 2 from the atmosphere 2. Carbon from trees will be released into the atmosphere as they decompose/ are burnt 2 (c) Wind turbines do not produce CO 2 when they generate electricity (1) However the manufacture of wind turbines requires carbon based energy (1) Transporting turbines to site/wind farm also requires carbon based fuels (1) 2 (a) Carbon dioxide equivalent allows us to compare the effect of methane and carbon dioxide on global warming 3 1 (b) kgco2eq = m(kg) x GWP/ 24 x 21 (1) = 504 gco2eq/ equivalent to 504 g CO 2 (1) Changes have lowered the carbon footprint of milk production (1) 3 (a) The total amount of greenhouse gases (1) produced to (directly and indirectly) support human activities (1) 3 2 (b) 20 x 11/100 (1) = 2.2 (1) tonnes 2 (c) (i) Fertiliser use 1 (ii) Any three from: Buy or grow organic food Reduce food wastage Buy locally produced food Eat less red meat Buy food sold loose/choose food in less packaging /buy from shops/meat counters where packaging is less 3 continued over page 13

15 4 (a) Install cavity wall insulation 1 (b) (i) Power is the rate of energy transfer/a measure of how quickly energy is transferred 1 Also accept: power = energy transferred/time (ii) 1. Units used (kwh) = power(kw) x time (h) (1) = (0.030x21) + (0.045x3) (1) =0.765 kwh 2. Difference = = (kwh) (1) In year 365 x = 115 (kwh) (1) Unnecessary mass CO 2 = x (1) = 60.3 kg (1) (Unit must be included to be awarded mark) 2 4 continued over page 14

16 5 (a) (i) 32 (1), 34 (1) respectively 2 (ii) Engine 1 Efficiency = =25% (1) x 100 (1) (Mark for substitution of data in to correct equation) 6 Engine 2 Efficiency = 2 x100 (Mark for correct reading of diagram to obtain 2 (1) 6 (1)) 6 =33.3% (1) Engine 2 is more efficient (1) Answer must follow calculated values. Allow error carried forward.. (iii) Less CO 2 is produced per litre of petrol (1) however the diesel engine has a much lower fuel consumption/approx half as much diesel needed as petrol to travel the same distance (1) The diesel engine has a lower carbon footprint/ data does not support statement (1) 3 Alternative response Petrol: CO 2 produced per km = 2.3/64 = (kg) (1) Diesel: CO 2 produced per km = 2.65/112 = (kg) (1) The diesel engine has a lower carbon footprint/ data does not support statement (1) (b) Any three from: Engine running while car is stationary/stopped in traffic Overcoming air resistance/ aerodynamic drag Overcoming inertia/braking loses Friction between the tyre and the road 3 continued over page 15

17 6 (a) (i) The process in which some gases absorb (thermal) radiation (1) from a planet s/earth s surface (1) and then radiate it out again in all directions (1) so keeping the temperature of the planet/earth warmer than it would otherwise be (1) 4 (ii),the temperature at the Earth s surface would be much lower without the greenhouse effect (1) making the Earth less able to sustain life (1) 2 (b) Climatic - Max of two marks Overall increase in Earth s temperature (1) Possibly more extreme weather (1) Environmental Max of four marks Melting of polar ice caps/glaciers (1) Sea levels may be raised (1) Desert regions may increase (1) Conditions for plants/animals will change (1) Some species which cannot adapt fast enough to (rapid) change (1) may become extinct (1) 6 Learning Outcomes LO1 LO2 LO3 LO4 LO5 Total % Actual (for the completed paper) Marks 16

18 TOTAL LO AC (a) 3 (b) 2 (c) 3 2(a) 1 (b) 1 2 3(a) 2 (b) 2 (c)(i) 1 (ii) 3 4(a) 1 (b)(i) 1 (ii) (a)(i) 2 (ii) (iii) (b) 3 6(a)(i) 4 (ii) 2 (b)