Overview: Washing hands is far more effective with warm water than cold. In some areas warm water is not available for washing hands so how can we create a system from rubbish? Bacteria colonies can grow much faster in warm water so we could make the problem worse. You can use Solar Water Disinfection (SoDis method ) which uses the Sun’s Ultra Violet light to kill bacteria, protozoa and viruses. There are two ways it works. One is if the temperature rises to above 70C and the second is the action of the Ultra Violet radiation itself that kills microorganisms by microorganisms are killed by disrupting their DNA. It is thought that this is one of the reasons why we get fewer colds and flu in summer than in winter. As the UV light penetrates water it becomes less intense and so is only effective for a short distance. So how might we produce a potentially clean warm hand wash station? Note: Unless you can verify the water is sterilised you cannot drink it as it may cause infections
Equipment Provided: Plastic bottles, silver foil/crisp packets, (agar plates, microscope, thermometer and UV beads (if available) tape, scissors
Health and Safety: You must carry out your own risk assessment (Rubbish Science accept no liability) Note: Do NOT drink the ‘clean’ water you have produced!
Things you might need to know / Questions you might ask:
- How might you ensure the suns rays penetrate the water to the maximum distance possible?
- How can you work out the path of the sun from shadows a stick makes?
- How might we use reflectors to increase the temperature of the water in the bottle?
- How might we know the water is sterile? Remember you can’t drink the water
- How might you record results to compare systems?
- What colour should the bottle be? Note: Painting it black will make it hotter, but there will be no UV penetration.
- How might you use UV beads that change colour in the presence of UV light to aid you with this investigation?
- Could you automate this system?
Prototyping: Develop some ideas and try them out. If a thermometer and/or UV beads are available then collect data. Which design seems to give the highest temperature rise?
Modifications: What modifications are you going to do based on what you learned from your prototypes?
Prediction: What do you think will happen and why?
Do it: Carry out your investigation
What happened?: Did you get results that supported your prediction?
Tell Someone: Explain what you did and why you felt your design was effective or not. Listen to others do they have any good ideas?
What did you learn? What were the key things you learned from the task. What would you do differently next time? Could you use what you learned to solve other problems?
Extension/Modify/Do it again: What would you do differently?
Possible Model – How can you optimise the design?