C1.25a Finding soot in the air You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations. Soot can be formed when fuels burn without enough oxygen. Soot is made up of tiny particles of carbon that float in the air. The particles are often too small to be seen without the aid of a microscope. You can use ‘sticky cards’ to find how much soot is in the air in various places. The ‘sticky cards’ are a plastic film with a sticky surface. The sticky side is protected by card when not in use.
Prediction 1
You can place the cards in different places – such as the school grounds, near a road junction etc. Which places do you think will have the most soot particles in the air?
Apparatus sticky tape
scissors
marker pen
microscope
microscope slides
double-sided sticky tape
acetate with graph paper printed on it
drawing pins or waterproof sticky tape
Health and safety ●
Be careful near traffic
●
Do not climb on anything to place your sticky strips
Method A Make your sticky cards by putting a piece of double-sided sticky tape onto each piece of acetate. Do not remove the backing on the double-sided sticky tape. B Choose some places where you expect the amount of soot pollution to be different. C Remove the backing from the double-sided sticky tape. Use a drawing pin or some waterproof sticky tape to fix the plastic so that the sticky side is open to the air. The plastic strip should be hung in a position where rain cannot affect it. D Leave the plastic strips for a few days. Record the time and place, and the length of time the plastic is exposed. At the end of the time cover the sticky side of the plastic strip with a piece of normal sticky tape. E Put the plastic strip on a clean microscope slide, and put the slide on the microscope stage. F
Put the microscope on the lowest magnification, and lower the lens to just above the card.
G Now look through the eyepiece and wind the lens upwards until you see the specks of soot inside the 1 mm squares on the cards. H Count how many particles of soot you can see in one square. If your card was in a place where it could have been splashed with mud, make sure you do not count any mud particles. I
Move the plastic strip on the stage so that you can see another square. Count the number of soot particles in the second square.
J
Repeat this for at least four more squares.
K Repeat the measurements for the plastic strips from the other locations.
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Sheet 1 of 2
C1.25a Finding soot in the air (cont.) Recording your results 2
Calculate the mean number of particles of soot in each square millimetre, ignoring any anomalous results for each location.
3
Draw a bar chart of your mean results for each location where the plastic strips were placed.
Considering your results/conclusions 4
Describe any patterns that you see in your results. Explain the patterns if you can.
Evaluation 5
How fair was your comparison between the different sites? Were there any factors you could not control?
6
How certain are you of your conclusions? Explain your answer.
Š Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.
Sheet 2 of 2
C1.25b Carbon monoxide and traffic Name
Class
Date
You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations. A group of students in a city school have been given three carbon monoxide measuring monitors (A, B and C). First they tested the air in the school playground. Then they went outside the school and took some more readings by a busy roundabout. The students predicted that they would find higher carbon monoxide concentrations near the roundabout because incomplete combustion occurs in vehicle engines. 1
What is the formula of carbon monoxide?
2
a Explain how carbon monoxide is produced in car engines. _______________________________________________________________ _______________________________________________________________ b Explain why it is dangerous to leave a car running in a garage with the door shut. _______________________________________________________________________________ Look at the measurements in Tables 1 and 2. Anomalous results are measurements that do not seem to fit the pattern of other measurements that are taken.
3
a Put a ring around the readings that could be anomalous. b Suggest why some of the readings are anomalous. ________________________________________________________________________________ 4
Work out the mean reading for each instrument in the two locations, leaving out the anomalous results. (Hint: add up the readings and divide the total by the number of readings used.) Write down the mean reading for each instrument in the table.
5
Calculate the overall mean amount of carbon monoxide in the two locations. Write your answers in the last row of each table.
6
a Use the mean values to write a conclusion for the investigation. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________ b
Suggest an explanation for what these results show. ________________________________________________________________________________ ________________________________________________________________________________ ________________________________________________________________________________
Š Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.
C1.25c Monitoring carbon monoxide You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations. Some of the pollution caused by vehicles is due to incomplete combustion occurring in their engines. A group of students at a city school were given three carbon monoxide monitors (A, B and C). They tested the air in the school playground and near a busy roundabout. 1
Look at the data in Tables 1 and 2, and give the location, instrument letter and reading number of any anomalous results.
2
What could cause anomalous results?
3
Calculate the mean for each instrument in the two locations. Do not include anomalous results in your calculations. Present your results in a table.
4
Why is it important to take a mean of several readings?
5
a How big is the difference in the means between each instrument? b Do you think this difference is significant? Explain your answer.
6
The largest and smallest readings, not counting anomalous results, at a location give the range within which the true value falls. State the range at the two locations.
7
The difference between two results is significant if the mean of each reading is outside the range of the other. Is the difference in carbon monoxide level at the two locations significant?
8
a
What is the cause of the carbon monoxide at the two locations likely to be? Explain in as much detail as you can.
b Suggest why the carbon monoxide levels are different in the two locations. 9
Your suggestion in 8b is a hypothesis to explain some experimental results. Describe how you would test your hypothesis.
Extra challenge 10 Catalytic converters were fitted to all new vehicles in the EU from the early 1990s. These devices remove carbon monoxide from vehicle exhausts. Suggest how the results obtained might have been different if the investigation had been carried out in 1990.
Š Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.