The shape of the lesson
By the end of the lesson, learners can
- How greenhouse gases trap energy: Extended.
- Photosynthesis and the carbon balance: Burning fuels, respiration and decay add carbon dioxide to the air; photosynthesis takes it out.
- Reducing climate change: Each strategy either cuts the release of a greenhouse gas or removes carbon dioxide from the air.
- Greenhouse gases: carbon dioxide and methane.
- Extended: absorb infrared from the surface, re-emit it, less lost to space.
- Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2.
- Strategies: trees, less livestock, fewer fossil fuels, hydrogen and renewables.
One picture every idea returns to
Carbon dioxide and methane are greenhouse gases: higher levels cause increased global warming, which leads to climate change. Extended: the Earth's surface absorbs energy from the Sun and emits thermal energy as infrared radiation; greenhouse gases absorb this infrared and re-emit it in all directions, including back towards the Earth, so less thermal energy is lost to space. Photosynthesis removes carbon dioxide: carbon dioxide + water → glucose + oxygen, using light energy in the presence of chlorophyll (Extended: 6CO2 + 6H2O → C6H12O6 + 6O2). Strategies to reduce climate change include planting trees, reducing livestock farming, decreasing the use of fossil fuels and increasing the use of hydrogen and renewable energy such as wind and solar.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, A warmer planet, explained.. Carbon dioxide and methane let sunlight in but slow the escape of heat. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: How greenhouse gases trap energy | Extended. | Whole class, then pairs |
| 13 to 21 min | Teach and check: Photosynthesis and the carbon balance | Burning fuels, respiration and decay add carbon dioxide to the air; photosynthesis takes it out. | Pairs |
| 21 to 30 min | Teach and check: Reducing climate change | Each strategy either cuts the release of a greenhouse gas or removes carbon dioxide from the air. | Connect-Extend-Challenge |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 16 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Reducing climate change, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Connect-Extend-Challenge
After the new idea, each student writes three lines: how it connects to what they knew, how it extends their thinking, and what still challenges them. Pairs compare, then the challenges become the plenary.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| The greenhouse effect is not the hole in the ozone layer, and acid rain does not cause global warming. | Do not write that greenhouse gases "reflect" heat back or "trap the Sun's rays": they absorb and re-emit infrared given off by the warm Earth. And the greenhouse effect itself is natural and keeps the Earth habitable; the problem is the increase in greenhouse gases. |
Greenhouse gases and climate change: worksheet
6 questions, 16 marks. Written in the style of the papers; no past paper question is reproduced.
Name two greenhouse gases and give one source of each.
(Extended) Explain how an increase in greenhouse gases causes global warming.
Write the word equation for photosynthesis and state the two conditions it needs.
(Extended) Calculate the mass of glucose made when 66 g of carbon dioxide is absorbed by photosynthesis. (Mr: CO2 = 44, C6H12O6 = 180)
Describe four strategies to reduce the effects of climate change and explain how each helps.
Suggest two consequences of climate change.
Answer key and marking notes
- Carbon dioxide: complete combustion of carbon-containing fuels.
- Methane: decomposing vegetation or waste gases from digestion in animals.
- The Earth's surface absorbs energy from the Sun and emits thermal energy as infrared radiation.
- Greenhouse gases absorb this infrared and re-emit it, some back towards the Earth.
- So less thermal energy is lost to space and the average temperature rises.
- carbon dioxide + water → glucose + oxygen
- Light energy and chlorophyll.
- Moles of CO2 = 66 ÷ 44 = 1.50 mol
- Moles of glucose = 1.50 ÷ 6 = 0.250 mol
- Mass of glucose = 0.250 × 180 = 45.0 g
- Planting trees: more photosynthesis removes carbon dioxide.
- Reducing livestock farming: less methane released.
- Decreasing the use of fossil fuels: less carbon dioxide released.
- Using hydrogen and renewable energy such as wind or solar: energy without carbon dioxide emissions.
- Rising sea levels from melting ice, causing flooding.
- More extreme weather (droughts, storms) and changes to where crops can be grown.
8 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which two gases are greenhouse gases that cause increased global warming?
- Acarbon dioxide and methane
- Bnitrogen and oxygen
- Csulfur dioxide and carbon monoxide
- Dargon and nitrogen dioxide
Which is the word equation for photosynthesis?
- Acarbon dioxide + water → glucose + oxygen
- Bglucose + oxygen → carbon dioxide + water
- Ccarbon dioxide + oxygen → glucose + water
- Dmethane + oxygen → carbon dioxide + water
Which strategy reduces climate change by lowering the amount of methane released?
- Areducing livestock farming
- Bplanting trees
- Cusing flue gas desulfurisation
- Dfitting catalytic converters to cars
The graph shows the concentration of carbon dioxide in the atmosphere from 1960 to 2020. By what percentage did it increase over this period?
- A30.6%
- B23.4%
- C97.0%
- D76.6%
Which change would reduce the amount of carbon dioxide released when electricity is generated?
- Areplacing coal-fired power stations with wind turbines and solar panels
- Busing low-sulfur coal
- Cfitting flue gas desulfurisation to the chimneys
- Dburning the coal in a limited supply of air
Which statement correctly explains how greenhouse gases cause global warming?
- Athey absorb infrared radiation emitted by the Earth's surface and re-emit some of it back towards the Earth
- Bthey reflect visible light from the Sun back into space
- Cthey make a hole in the ozone layer that lets in more heat
- Dthey react with oxygen in an exothermic reaction that heats the air
Which is the balanced symbol equation for photosynthesis?
- A6CO2 + 6H2O → C6H12O6 + 6O2
- BC6H12O6 + 6O2 → 6CO2 + 6H2O
- C6CO2 + 6H2O → C6H12O6 + 3O2
- DCO2 + H2O → C6H12O6 + O2
What mass of glucose is made when 132 g of carbon dioxide is used in photosynthesis? (Mr: CO2 = 44, C6H12O6 = 180)
- A90.0 g
- B540 g
- C180 g
- D15.0 g
Quiz key
Carbon dioxide and methane are the greenhouse gases in the syllabus; higher levels cause increased global warming, which leads to climate change. Nitrogen and oxygen are the main gases of clean air. Sulfur dioxide causes acid rain and carbon monoxide is toxic. Argon is an unreactive noble gas, and nitrogen dioxide causes acid rain and smog.
Plants use light energy and chlorophyll to turn carbon dioxide and water into glucose and oxygen. The reverse equation is respiration. Oxygen is a product, not a reactant, so the third equation is wrong. The last equation is the combustion of methane.
Methane is released from the digestion of livestock such as cattle, so reducing livestock farming lowers methane emissions. Planting trees removes carbon dioxide, not methane. Flue gas desulfurisation removes sulfur dioxide. Catalytic converters remove carbon monoxide and oxides of nitrogen.
The increase is 414 − 317 = 97 ppm, and 97 ÷ 317 × 100 = 30.6%. 23.4% divides the increase by the final value (414) instead of the starting value. 97.0% is the increase in ppm, not a percentage. 76.6% is 317 as a percentage of 414.
Wind and solar power generate electricity without burning fuel, so no carbon dioxide is released. Low-sulfur coal and flue gas desulfurisation reduce sulfur dioxide, not carbon dioxide. Burning coal in a limited supply of air still releases carbon, but now partly as toxic carbon monoxide and particulates.
The warm surface emits thermal energy as infrared; greenhouse gases absorb it and re-emit it in all directions, including back to the Earth, so less energy is lost to space. Reflecting sunlight back to space would cool the Earth. Ozone depletion is a different problem caused by CFCs and is not the greenhouse effect. Carbon dioxide and methane do not warm the air by reacting with oxygen in the atmosphere.
6CO2 + 6H2O has 6 C, 12 H and 18 O; C6H12O6 + 6O2 also has 6 C, 12 H and 18 O, so it is balanced. The second equation is respiration, the reverse process. The third has only 12 O on the right. The fourth uses correct formulae but is not balanced.
Moles of CO2 = 132 ÷ 44 = 3.00 mol. The equation needs 6 mol CO2 per 1 mol glucose, so 3.00 ÷ 6 = 0.500 mol glucose, and 0.500 × 180 = 90.0 g. 540 g uses a 1 : 1 ratio (3.00 × 180). 180 g is the mass of one mole of glucose, ignoring the data. 15.0 g divides 90.0 g by 6 a second time.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.