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Rough Science 5: Survival

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Curriculum link

KS3 QCA Scheme of Work Unit 7F
How acids react with carbonates.
The evidence for a reaction, and the test for carbon dioxide.
Acids, alkalis and indicators.
The space station's CO2 cleaner has failed, and CO2 is rising to dangerous levels. Can pupils design and test a home made device to remove CO2 from the air in time?

Running the activity

Introduce the context with the Final Mission Briefing sheet (page 1). You could stick this on the door before pupils enter the laboratory, and/or display it on the data projector or OHT.
Carbon dioxide scrubber

Page 2 - pupils receive a message that the CO2 scrubber that purifies the air is failing.
Pupils are given help to design the three different parts of a test scrubber. The challenge is to choose suitable chemicals from those available, and then test them to see how well the scrubber works. The Mission message sheet contains instructions to structure the challenge.
You may want pupils to research the information they need. The CO2 scrubber consists of three parts, assembled using standard laboratory equipment.

Part A: CO2 Generator. Various chemicals are made available to pupils. They should choose the ones that react together to make CO2, for example marble chips and dilute hydrochloric acid.

Part B: CO2 Scrubber. Various chemicals are made available to pupils. They should test the chemicals to find out which are alkali, and try them as potential scrubbing chemicals. Two forms of alkali are suggested (see Technician Notes). Solid forms work extremely well but are more hazardous, and solutions which are less effective but significantly less hazardous. Pupils should find that only soda lime or sodium/potassium solution will absorb.

Part C: CO2 Tester. The pupils should choose limewater from various options provided, as a test for the gas. Having designed their scrubber pupils should show you their plan. If they have selected inappropriate chemicals, ask them to rethink their design. Their first experiment should be a control, to see how quickly (in the absence of a scrubbing chemical) the limewater turns milky nonce CO2 is generated. It is important that the rate of production of CO2 bubbles should be slow (particularly if you are using alkalis in solution form). This is so the scrubber has enough time with to react with the CO2 before it passes through the tube. Pupils then repeat the experiment with each scrubbing chemical in turn. The best scrubber is the one where the limewater takes longest to go milky.

More ideas
Give the activity a competitive element. The winner is the group that finds the solution in the shortest time
(and thus prevents the crew suffocating).

Discuss the Apollo 13 mission, where a disaster very similar to this one happened. The event was made into a very popular film.

Web links

News links

Rough Science

The new series of Rough Science

Association for Science Education

This activity was adapted from a longer activity on the ASE Science Year CD-ROM 2 Is there Life? The activity was called Space Station Survival.

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