GCSE COMBINED SCIENCE: TRILOGY Higher Tier Chemistry Paper 1H

This question is about the extraction of aluminium. An aluminium atom is represented as: Al1327 Give the number of electrons and neutrons in the aluminium atom. [2 marks] Number of electrons Number of neutrons Aluminium is extracted by the electrolysis of a molten mixture of aluminium oxide and cryolite. Figure 1 shows the cell used for the electrolysis. Figure 1 Aluminium is produced by the reduction of aluminium oxide (Al2O3). What is meant by the term reduction? Oxygen is formed at the positive carbon electrodes. Explain why the positive carbon electrodes must be continually replaced. [3 marks] A substance conducts electricity because of free moving, charged particles. What are the free moving, charged particles in a: • carbon electrode (made from graphite) • molten mixture of aluminium oxide and cryolite • metal wire? [3 marks] Carbon electrode (made from graphite) Molten mixture of aluminium oxide and cryolite Metal wire Turn over for the next question This question is about substances with covalent bonding. Figure 2 shows a ball and stick model of a water molecule (H2O). Figure 2 Suggest one limitation of using a ball and stick model for a water molecule. [1 mark] Ice has a low melting point. Water molecules in ice are held together by intermolecular forces. Complete the sentence. [1 mark] Ice has a low melting point because the intermolecular forces are .