Silicon dioxide (silica) melts at 1710 °C. Poly(ethene) softens at about 120 °C. Methane boils at −162 °C.
Explain the differences in these temperatures.
Refer to the structure and bonding of each substance.
[6 marks]AQA GCSE Chemistry November 2020 Paper 2F
5 questions on this paper's topics
30:001 of 5
A student investigates how the concentration of hydrochloric acid affects the rate of its reaction with magnesium ribbon. Hydrogen gas is produced.
Plan an investigation using a gas collection method.
Include the variables the student should control.
[6 marks]A student has samples of tap water, sea water and rain water.
Plan an investigation to compare the pH and the mass of dissolved solids in the three samples, and to purify the sea water by distillation.
[6 marks]Sodium chloride solutions are used in hospitals.
.1
0.80 g of sodium chloride is dissolved in water to make 40 cm³ of solution. Calculate the concentration in g/dm³.
[2 marks].2
A nurse needs 250 cm³ of a solution with a concentration of 9.0 g/dm³. Calculate the mass of sodium chloride needed.
[3 marks]Crude oil is separated into fractions in a fractionating column.
Explain how fractional distillation separates crude oil into fractions.
[6 marks]