A sample contains very long covalent molecules. It softens when heated, does not conduct electricity and becomes solid again on cooling.
Explain these observations using a polymer model.
[6 marks]Edexcel GCSE Chemistry November 2020 Paper 2H
5 questions on this paper's topics
24:001 of 5
A reaction uses the same solution concentration at 20 °C and 35 °C. A student explains the faster reaction at 35 °C by saying particles are larger and the activation energy has decreased.
Evaluate the explanation.
[4 marks]A student adds an alkali gradually to an acid. The measured pH values after successive additions are 2, 4, 6, 7, 9 and 11.
.1
Describe the change and identify the neutral reading.
[2 marks].2
Explain neutralisation in terms of the reacting ions.
[2 marks]A company claims that because its hydrocarbon fuel burns with no smoke it causes neither acid rain nor climate change. The fuel contains small amounts of sulfur and is burned at high temperature in air.
Evaluate the claim using the possible gaseous products.
[4 marks]Three repeated demonstrations with equal samples of a group 1 metal collect hydrogen volumes of 47, 49 and 48 cm³. A separate run collects 31 cm³ after the gas tube becomes loose.
.1
Calculate the mean volume from the three valid repeated demonstrations.
[3 marks].2
Explain why the low run cannot show that the metal was less reactive.
[2 marks]