1a) i) They didn’t have the right equipment as it hadn’t been invented then. (1)
ii) Reaction is endothermic (1)
iii) Other scientists could not repeat his results (1)
iii) Aluminium chloride + potassium goes to Potassium chloride and aluminium (1)
b) He found the properties of aluminium and compared them to the properties of the previously discovered metals. He realised properties were different so must have been a new metal. (2)
2a) i) Relative formula mass MgO = 24 + 16 = 40 (2)
ii) Percentage mass of Mg = 60% (2)
iii) Mass of Mg from 25g MgO = 15g (1)
b) i) Some MgO lost when students lifted the lid (1). Not all of the Mg ribbon reacted when the students thought it had (1). Other answers as well (out of 2)
ii) It was more reliable as they could compare the data to check for a pattern and discard any anomalous results (2).
3a) Mg (2, 8, 2) and Cl (2, 8, 8) drawn. (2)
b) Filter (1)
ii) Hydrochloric Acid (1)
c) Ions are mobile (1)
ii) Chlorine ions lose electrons (1)
iii) Mg2+ + 2e- goes to Mg (1) (OR Mg2+ goes to mg - 2e-)
4. Fe2O3¬ (4)
5a) Giant structures containing layers of metal atoms. Free, delocalised electrons. (3)
i) Free electrons carry the heat (1)
b) i) Much smaller (1)
ii) Can fit into smaller gaps than normal-sized atoms (1) (Larger surface area?? make your own minds up, refer to conversation on p9 and 10 to see the debate!)
6a) Covalent (1)
b) More reactant molecules than product molecules (1)
ii) Reaction is exothermic (1)
c) More particles in the same volume of gas which means there is more chance of collisions, increasing the rate of reaction. (2)
d) Ethanol held together by weak intermolecular forces which require little energy to break (2)
7a) i) Graphene is strong as it has a giant lattice structure. Each carbon atoms is joined to 3 others by strong covalent bonds which require a lot of energy (force) to break. (3)
ii) Each carbon only joined to 3 other carbon atoms so free electrons carry the electric current through the graphene. (2)
iii) Screen would no longer be transparent/ layers would slide off meaning you get graphite all over your hands!!! (1)
Please post any improvements.