Challenge students to extract drinking water from damp sand, a real desert survival scenario
Your aircraft has crashed in the desert! Your last cup of water spilled into the sand, so you scoop up the wet sand and need to separate it again.
This experiment should take 90 minutes.
- Plastic bags
- Yoghurt pots
- Aluminium foil
- Aluminium foil trays
- Beer cans
- Plastic lemonade bottler
- Rubber bands
- An old pair of tights
- Blocks of expanded polystyrene or foam rubber
- Craft knives
- Furthermore, the desert environment provides unlimited quantities of sand, and a source of radiant energy – a lamp should be provided to simulate the desert sun.
Health, safety and technical notes
- Read our standard health and safety guidance here.
- Wear clothing protection if desired.
- A lamp with a 60W bulb is needed to simulate the desert sun (check that it is safely wired and earthed).
- Wet sand is made up of 100g sand mixed with 25 cm3 water per bag.
- This is an open-ended problem-solving activity, so the guidance given here is necessarily incomplete.
- Please consider the dangers of using water near electric mains.
- There should be no need for eye protection; unless the separation method chosen takes an unusual turn.
- Some help on colling steam may be necessary.
Some suggested approaches are outlined below. More advice on how to use these resources can be found here.
- A wide, clear plastic tube could be provided, so that the principle of extraction of water using centrifugal force could be explored, like a spin dryer.
- A plastic dish covered in foil could be used with a sealed porous pot inside containing the wet sand.
- The bottom of the dish should be insulated.
- At the top, a lamp is shone on the dish.
Taped interviews conducted with the ‘survivors’ of the plane crash on their return to the UK by science reporters. The novel water ‘extractors’ already making headline news need the students’ personalised explanations.
Evaluation of task
These are suggestions only:
- Just before they are about to die, the ‘survivors’ (groups) present the water they have freed from the sand.
- Measure the volume of water collected by each group. The winning group is that with the largest volume of water.
- In the event of a tie, the group with the most appetising sample of water will be declared the winners.
Cross-curricular possibilities with the geography department – ie water supply in desert regions.
The resources were originally published in the book In Search of Solution P. Borrows, K. Davies and R. Lewin, Royal Society of Chemistry, 1990.