Science at key stage 3 (Year 8)
Unit 8B: Respiration
Section 4: d. How do cells use the food molecules absorbed after digestion?
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Objectives |
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- to use thermometers of different kinds
- that respiration can be represented by a word equation: glucose + oxygen > carbon dioxide + water, and this reaction releases energy
- to explain observations using scientific knowledge and understanding
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Activities |
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Outcomes |
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Children: |
- Present pupils with a range of observation activities,
eg
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observing a temperature difference between germinating peas and boiled peas
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yeast generating bubbles of carbon dioxide which are passed into lime water
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germinating peas and maggots in separate gauze cages over hydrogencarbonate indicator
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water weed shielded by black paper in hydrogencarbonate solution producing carbon dioxide
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measuring their own temperature
- Discuss their observations to establish that the hydrogencarbonate indicators show that the living material was producing carbon dioxide and the increased temperature measured by the thermometers shows that the living material was also releasing energy. Provide pupils with opportunities to discuss, in groups, what they observe and provide an explanation to the whole class.
- Explain that energy is released in cells by respiration, which is a process that uses nutrients from food and oxygen, and releases carbon dioxide, water and energy. Summarise the process of aerobic respiration in a word equation.
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- record temperatures, reading scales accurately
- summarise respiration in a word equation: glucose + oxygen > carbon dioxide + water
- explain the increased temperature in terms of energy release during respiration
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Points to note |
- Teachers will need to explain the use of the hydrogencarbonate indicator if pupils have not used it previously.
- Pupils' attitudes to the appropriate care of living organisms need to be handled sensitively.
- Sensors and computer software can be used to monitor temperature and other changes in germinating peas.
- Pupils with visual impairment could use talking thermometers to record temperature.
- Extension: some pupils' understanding of aerobic respiration could be reinforced using a 'snap' game with cards labelled 'glucose', 'oxygen', 'carbon dioxide', 'water' and a different coloured card for 'energy'.
Safety
- the safe approach (including everyday use) to taking body temperature is to use liquid-crystal strips. If clinical thermometers are used, they need to be disinfected each time they are used
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This unit is divided into sections. Each section contains a sequence of
activities with related objectives and outcomes. You can view this unit by
moving through the sections or print/download the whole unit.
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