Are winter tyres better than summer tyres?
Have you ever wondered why some colleagues rush to swap the tyres on their car as soon as the temperature drops? Have you ever discussed the question about which is best and how they are different with students during the polymers section of the Key Stage 4 curriculum (or in A level chemistry)?
This clip (http://www.youtube.com/watch?v=elP_34ltdWI) shows a practical comparison of the driving qualities of two cars in icy conditions; one car is fitted with summer tyres (the usual default type in the UK) and one is fitted with winter tyres.
What are the differences between the two types of tyre and how do these contribute to the different performance as demonstrated by the clip? In addition to the tread pattern of the winter tyres, the rubber compound used is specially formulated so that it performs better at lower temperatures, temperatures at which summer tyres are not able to maintain a good grip on the road. This is achieved by increasing the amount of pure rubber added to the mix alongside the usual vulcanised rubber. The website http://www.bouncing-balls.com/index2.htm provides information about the production of rubber and the vulcanisation process which will help students to understand the processes involved.
Alternatively, if you want to show the effect of cross linking latex chains practically, the ‘Fantastic Plastic’ resource from the Science Enhancement Programme gives both background information and detailed practical instructions to enable students to make their own rubber bands and rubber balls. It can be downloaded from the STEM elibrary at: http://www.nationalstemcentre.org.uk/elibrary/science/resource/2374/fantastic-plastic