Rubbish Science at Le Rosey Festival of Education

We were asked to deliver a session to 75 Le Rosey students as part of their Festival of Education 2019.) If you want us to deliver a session at your school please get in contact.)

As usual many students expressed their fear of failure, particularly public failure and so we got one who expressed this fear to fail in front of others to show it wasn’t too bad!

Rubbish Science encourages taking risks and pushing things to the limits to see where they break. Then optimising solutions. The session was only a short one so we looked at the solar handwash station and set the target to create the highest temperature whilst still allowing UV penetration from sunlight. The example below wasn’t given to the students. It shows several optimising features:

  • The bottle is tilted at 90 degrees to the Sun to get maximum exposure
  • Putting the water bottle inside the bigger bottle adds the greenhouse effect to the temperature rise
  • The crisp packet acts as a reflector and the bigger the reflector the more sunlight hits the water bottle
  • Putting the reflector inside rather than outside of the bigger bottle should be slightly more effective as if it is on the outside, the light will have to pass through the outside plastic layer twice – although this will be offset as the bottle will be warmed more.

The students were very engaged and came up with some great ideas. We left the bottles until the end of the day before taking final readings, but unfortunately, it got cloudy so the temperatures had all dropped considerably from their highest which I recorded as 51 C

Of particular note was the group of students who created effectively a solar cooker. They noticed the sun was shining onto the roof of Le Roseys Space Ship like building and so put their handwash station at the maximum brightness

Unfortunately, this position changed during the day. Due to the large volume of water they used, their temperature rise wasn’t the greatest, but it was a fantastic design idea.

Results :

So why the disparity in temperatures? Partly down to the design but also the volume of water used. Knowing about Specific Heat Capacity and applying it the best option is a small volume of water.

Which was the best solution? We would need to carry out further investigations using the same volumes of water and the same position etc. As usual Rubbish Science projects are never finished and can always be improved. It is the journey, not the destination that is important.

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