Science at key stage 3 (Year 8)
Unit 8C: Microbes and disease
Section 2: b. What are micro-organisms and how do we grow them?
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Objectives |
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- to share ideas and information, carry out the task and then review ideas
- to decide what to measure
- how to control variables
- about the number of measurements needed for data in which they have confidence
- that yeast respires like other organisms
- to collaborate with other investigative groups to gather reliable data and draw valid conclusions
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Activities |
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Outcomes |
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Children: |
- Ask pupils what they know about yeast from advertisements they may have seen,
eg yeast respiration causing bread dough to rise. Discuss with them how they could investigate how increasing the quantity of sugar affects the quantity of carbon dioxide released,
eg by placing a yeast/flour/glucose dough in a measuring cylinder in a warm environment, or by collecting bubbles from a yeast/glucose suspension.
- Help pupils to plan an investigation so that together they obtain sufficient valid and reliable data.
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- evaluate methods proposed and agree on a common approach
- identify variables they need to control
- work out how many measurements will be obtained and indicate whether they will have confidence in their results
- explain that carbon dioxide is produced during aerobic respiration
- collect and store reliable and valid data using the same methodology
- identify a trend in the data,
eg the more sugar is added, the greater the volume
- relate results to scientific knowledge and understanding,
eg increase in volume is due to carbon dioxide produced in respiration
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Points to note |
- Pupils may have made bread with or without yeast in key stage 2, and tried keeping yeast and sugar in a warm and in a cold place and testing the gas produced.
- The effect of sugar on yeast activity can be observed in a limited period if the yeast is fully active before starting, and the solutions are pre-warmed and quantities of materials,
eg flour, glucose, are dispensed in advance. Groups of pupils will need to collaborate to obtain a sufficiently wide range of values, including repeat measurements, to draw conclusions.
- This relates to work on respiration in unit 8B 'Respiration'.
Safety
- school-based training in aseptic techniques for staff may be necessary. All work with micro-organisms should be carried out only after appropriate risk assessments have been consulted
- pupils' plans must be checked for health and safety before practical work begins. Ensure that plans do not involve a totally sealed system
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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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