C1.33a Discovering PTFE You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations. Poly(tetrafluoroethene) (PTFE) is a polymer made from the monomer tetrafluoroethene. PTFE was invented by accident by a chemist called Roy Plunkett. Plunkett worked for DuPont, an American chemical company. The sentences below tell the story. A Roy Plunkett was trying to make new non-toxic gases to cool fridges and freezers. He had already made some tetrafluoroethene, which he stored in a gas cylinder. B He sawed the cylinder in half and found a waxy, white powder inside. He realised that the tetrafluoroethene might have formed a polymer. C At first, Plunkett thought that the gas had leaked out of the cylinder. D He carried out further experiments to show it was a polymer. E One day he opened the cylinder but no gas came out. F
1
Later, he decided to check if the cylinder was really empty. He investigated further.
Write the letters for the sentences in the correct order to tell the story. Start with sentence A.
PTFE has special properties. It is very unreactive, non-toxic, very slippery and non-stick. DuPont make PTFE under the trade name of Teflon®. Teflon® has many uses. 2
What is the monomer used to make PTFE?
3
Which two of the following words could be used to describe tetrafluoroethene? Circle your answers. monomer
polymer
saturated
unsaturated
4
Why might Plunkett have just ignored the fact that he could not obtain any tetrafluoroethene from the cylinder?
5
Give three uses for PTFE.
6
a
Write down the names of three other polymers.
b
Give one use for each of the polymers you named in part a.
© Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.
C1.33b An accidental discovery You do not need to remember the details on this sheet for your exam, but you could be asked to apply your knowledge to unfamiliar situations. Poly(tetrafluoroethene) (PTFE) is a polymer made from the monomer tetrafluoroethene. The structure of PTFE is shown here. PTFE was invented in 1938 by the chemist Roy Plunkett. He was working for the American chemical company DuPont. It was invented by accident. He was trying to make new non-toxic gases to cool fridges and freezers. He had already made some tetrafluoroethene, which he stored in a gas cylinder. One F F day he opened the cylinder but no gas came out. At first, Plunkett thought the gas had leaked out of the cylinder. Later, he decided to investigate further. He sawed the C C cylinder in half and found a waxy, white powder inside. F F n Some polymers were known about at that time and Plunkett realised that the tetrafluoroethene might have formed a polymer. Plunkett carried out further experiments poly(tetrafluoroethene) PTFE to show that it was a polymer. Other chemists at DuPont investigated the best way of making PTFE, and if other polymers could be made in a similar way.
PTFE was found to have special properties. It was very unreactive and very slippery. It was also non-toxic and non-stick, with a high melting point. DuPont make PTFE under the trade name of Teflon®. Teflon® has many uses, including coating the inside of frying pans, in stainproof carpets and tape for plumbing joints. Roy Plunkett’s accidental discovery has led to a very useful material and a multimillion pound industry. 1
Define the words ‘polymer’ and ‘monomer’.
2
a
Draw the structure of tetrafluoroethene.
b
What is the formula of tetrafluoroethene?
3
What does tetrafluoroethene contain that allows it to form a polymer? (Hint: think about what the name tells you about its structure.)
4
Which of the following words could be used to describe tetrafluoroethene? monomer
polymer
saturated
unsaturated
5
Write an equation for the formation of PTFE.
6
Explain how the invention of PTFE was accidental.
7
a
What did DuPont do when Plunkett realised he had made a polymer?
b
Why did DuPont do this?
8
Suggest why PTFE is good to use as the coating on the inside of frying pans.
9
a
Write down the names of three other polymers.
b
Give one use for each of the polymers you named in part a.
Extra challenge 10 Suggest why manufacturers found it difficult to find a way of using PTFE to coat the inside of frying pans.
© Pearson Education 2010. Edexcel GCSE Science Activity Pack This document may have been altered from the original.