A sports company compares materials for the sole of a climbing shoe. Fig. 1 shows a simple molecular model of a rubber-like polymer before and after sulfur ...
Question 1 Report
A sports company compares materials for the sole of a climbing shoe. Fig. 1 shows a simple molecular model of a rubber-like polymer before and after sulfur links are added between chains. This process is called vulcanising. The links make the material less likely to stretch too far on hot rock.
(a) Name the substance type made from long chains of repeating units. [1]
(b) Suggest why sulfur links make the sole less stretchy. [2]
(c) Give one property, other than being less stretchy, needed for a climbing-shoe sole. [1]
This figure is a dot-and-cross diagram for one molecule of ammonia, NH3, made during the manufacture of fertiliser. Nitrogen and hydrogen are non-metals. The dots are electrons from nitrogen and the crosses are electrons from hydrogen. A technician compares ammonia with an ionic fertiliser before deciding how it should be stored.
(a) Complete the sentence. Each N-H bond is formed by a shared pair of electrons. This is a ______ bond. [1]
(b) What is the total number of hydrogen atoms in two molecules of ammonia? [1]
(c) Suggest why ammonia has a much lower melting point than sodium chloride. [2]
Answer Details
Vulcanised rubber
- (a) Long chains of repeating units make a polymer. [1]
- (b) Sulfur forms cross-links between chains. [1] The chains cannot slide past each other as easily, so the material is less stretchy. [1]
- (c) A suitable sole should also be tough, hard-wearing, have high friction, or be flexible. [1]
Ammonia
- (a) A shared pair of electrons forms a covalent bond. [1]
- (b) \(2\times3=6\), so there are 6 hydrogen atoms. [1]
- (c) Ammonia consists of small, simple molecules. [1] Only weak forces between molecules need to be overcome when it melts, unlike the strong ionic attractions in sodium chloride. [1]
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