CHEMISTRY HIGHER AQA. 33 Chemistry of the atmosphere: Greenhouse gases. Specification links. Learning objectives. Starter activity.

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1 33 Chemistry of the atmosphere: Greenhouse gases To describe the greenhouse effect To describe activities which increase amounts of greenhouse gases in the atmosphere To evaluate the quality of evidence To describe the effects of global climate change To describe actions to reduce emissions of greenhouse gases Specification links , , , WS: 1.3, 1.4, 1.5, 3.7 MS: 1a, 1c, 3c, 4a Starter activity The greenhouse gases; 5 minutes; page 210 Ask the student to identify some greenhouse gases and the effect they have on global temperatures. (The role of carbon dioxide in climate change is covered in Key Stage 3 science.) Discuss changes in carbon dioxide concentration. You could compare these changes to the relative stability of the atmosphere over the past 200 million years. Main activities The greenhouse effect; 20 minutes; page 211 Discuss how greenhouse gases trap heat energy in the atmosphere. Ensure that the student understands that the gas molecules absorb the heat energy and trap it in the atmosphere, and that this happens throughout the atmosphere; the reflection of heat by a layer of greenhouse gases in the upper atmosphere is a common misconception. Explain the role of greenhouse gases in keeping the Earth at a temperature suitable for life. Climate change; 20 minutes; page 212 Explain that some human activities increase amounts of greenhouse gases in the atmosphere (namely carbon dioxide and methane) and that many people think this increase in greenhouse gases is responsible for increasing global temperatures and climate change. Discuss the environmental implications of global climate change, such as rising sea levels, flooding, changes in habitats for plants and animals and potential problems for crops and food supplies. Explain why it is difficult to determine the quality of such evidence and misrepresentation of it. Plenary activity Changes; 5 minutes Swap roles with the student and ask them to devise three questions (plus answers) to summarise this lesson s content. Possible questions are: describe the greenhouse effect in terms of long and short wave radiation in the Earth s atmosphere; name three possible outcomes of global climate change; why is it important that people are informed about global climate change? Homework activity Carbon footprint; 60 minutes; page 213 Explain to the student that the carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the life cycle of a product. Full instructions are provided on the activity sheet. Support ideas The greenhouse effect The student may need reminding of calculations involving gas volume, as in lesson 16. Climate change The student may need help in understanding that valid evidence should be repeatable and precise and it is difficult to control variables in factors affecting climate change. Extension ideas Carbon footprint The student can investigate life cycle assessments in preparation for lesson 36. The student can use the Levi s website to read about methods used to reduce their carbon footprint and make their product more sustainable. Progress and observations 209

2 Starter activity: The greenhouse gases Time 5 To name the greenhouse gases To interpret graphs showing recent changes in carbon dioxide concentration calculator 1. What is a greenhouse gas? 2. Name three gases in the atmosphere that act as greenhouse gases. 3. The graph shows carbon dioxide concentrations in the atmosphere since 2012, at Mauna Loa in Hawaii. 405 Mean CO 2 at Mauna Loa parts per million a) What is 400 parts per million as a percentage? b) By how many parts per million did the carbon dioxide concentration change between 2012 and 2016? c) Before the industrial revolution in the 1800s, carbon dioxide made up 0.028% of the atmosphere. What is this in parts per million? 210

3 Main activity: The greenhouse effect Time 20 To know that greenhouse gases maintain the temperature on Earth at a level suitable for life To explain the greenhouse effect in terms of long and short wavelengths of radiation interacting with matter none 1. Use the diagram to explain the greenhouse effect. Your answer should include the words long wave, short wave, and radiation. 2. The average temperature on Earth is 15 C. Scientists estimate that without water vapour, carbon dioxide and methane in the atmosphere, the average temperature would be 18 C. a) Explain why the Earth would be cooler without greenhouse gases. b) How would the diagram have to change to show an atmosphere with no greenhouse gases? 211

4 Main activity: Climate change Time 20 To name human activities which increase amounts of greenhouse gases in the atmosphere To know that increases in amounts of greenhouse gases in the atmosphere may cause global climate change To describe some effects of climate change To evaluate the quality of evidence none The graph shows average global temperatures since By how much has the average temperature increased between 1880 and 2010? 2. How does this graph compare with the change shown in the graph in the starter activity? global average temperature ( C) 5 year average year 3. Name two human activities that increase the amount of the following gases in the atmosphere: a) carbon dioxide b) methane 4. Describe to your tutor the four effects of global climate change. 5. Scientists generally agree about how greenhouse gases work in the atmosphere, but not everyone agrees that human activity which increases amounts of carbon dioxide and methane in the atmosphere is causing average temperatures to rise or leading to climate change. Why is it difficult to provide good quality evidence that humans are causing climate change? Discuss with your tutor. 6. Read this extract from a newspaper report: Scientists have measured an average global temperature rise of 0.5 C over the past 35 years. This rise is thought to be responsible for the increase in heat waves, drought, flooding and damage to crops and coral reefs. Scientists are predicting that a 2.0 C rise in average global temperatures will cause a more dangerous change in climate. They are warning that some low lying countries may be wiped out altogether. a) Name one fact in this report that is certain. b) Name two uncertain pieces of information in this report and explain why they have uncertainties. c) Why is it important that newspapers publish this information? 212

5 Homework activity: Carbon footprint Time 60 To describe the carbon footprint of a product and how it can be reduced To describe actions to reduce emissions of carbon dioxide and methane To explain why action may be limited calculator The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product. The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane. A typical pair of denim jeans produces 33.4 kg of carbon dioxide over its lifetime. This is from harvesting the cotton, through to disposal of the jeans, and includes manufacture and care such as washing. An average T-shirt produces 6.0 kg of carbon dioxide over its lifetime mol of gas occupies 24 dm 3 at room temperature and pressure. Calculate the volume of carbon dioxide produced over the lifetime of: a) a pair of jeans b) a T-shirt. 2. Suggest how jeans manufacturers can reduce the carbon footprint of a pair of jeans. 3. How can the owner of the jeans reduce the carbon footprint? 4. Some clothing manufacturers are not very willing to reduce their carbon footprint. Suggest why. 213

6 33 Answers Starter activity: The greenhouse gases 1. A gas in the atmosphere that absorbs long wave radiation and helps to maintain temperatures on Earth that are high enough to support life 2. Carbon dioxide, methane, water vapour 3. a) 0.04% b) 10 ppm c) 280 ppm Main activity: The greenhouse effect 1. The answer should include the following points: radiation from the Sun reaching Earth is short wave radiation short wave radiation passes through the Earth s atmosphere; some is absorbed by the Earth longer wave radiation is emitted from the Earth some longer wave radiation escapes the atmosphere, some is absorbed by molecules of greenhouse gases 2. a) Greenhouse gases in the atmosphere absorb heat energy and radiate it back to the Earth s surface. Without greenhouse gases, this heat energy would escape the atmosphere and the Earth would be cooler. b) The diagram would show all longer wave radiation escaping the atmosphere. Main activity: Climate change /1.2 C 2. Both show an increase in the dependent variable. 3. a) For example, burning fossil fuels and clearing forests b) For example, rearing cattle for the meat industry and gas emitted from landfill deposits 4. For example, rising sea levels, melting ice, changes in habitat for some species, creation of desert areas 5. There are many variables, such as volcanic activity and particulate matter in the atmosphere, that are difficult to control; the Earth s climate has changed many times in the past 6. a) An average global temperature rise of 0.5 C over the past 35 years b) The 0.5 C rise is thought to cause the increase in heat waves etc. this is uncertain because there may be other causes, such as natural global cycles and volcanic activity. A rise of 2.0 C may cause more dangerous climate change this is uncertain because we do not know if a 2.0 C rise will have this effect, as there is no direct evidence. c) So that people/governments can prepare for the effects of climate change, such as developing new crops, flood defences, etc. Homework activity: Carbon footprint 1. a) g 24 dm 3 = dm 3 44 g b) 6000 g 44 g 24 dm3 = 3273 dm 3 2. Use alternative energy sources to farm the cotton, power the manufacturing process and power the retail process (delivery) 3. Wash the jeans less frequently and/or at a lower temperature; recycle the jeans when they are too old to wear 4. It can be expensive to make changes to processes to lower carbon footprint 214