Fig. 1 shows a delivery box containing two samples used in a school practical. Sample A is solid iodine and sample B is a small piece of diamond. The box is...
Question 1 Report
Fig. 1 shows a delivery box containing two samples used in a school practical. Sample A is solid iodine and sample B is a small piece of diamond. The box is kept dry. When iodine is warmed gently, purple vapour forms. Diamond does not melt in the same apparatus. Both samples contain only non-metal atoms and have covalent bonds, but their structures are different. The teacher asks students to relate their observations to the forces or bonds that must be overcome.
(a) Name the type of structure in iodine. [1]
(b) Describe the change when solid iodine forms vapour. [1]
(c) Explain why diamond has a much higher melting temperature than iodine. [2]
Answer Details
(a) Iodine has a simple molecular structure. [1]
(b) When iodine forms vapour, its molecules move farther apart as it changes from a solid to a gas. [1]
(c) Diamond has a giant covalent structure with strong covalent bonds throughout. Iodine consists of molecules with weak intermolecular forces between them. Much more energy is needed to break enough bonds in diamond, so it has a much higher melting temperature. [2]
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