9.1 Properties of metals
1. How does the thermal conductivity of metals generally compare to that of non-metals?
Metals are generally good thermal conductors, whereas non-metals are typically poor thermal conductors.
2. Compare the electrical conductivity of metals and non-metals.
Metals are good electrical conductors, while non-metals are generally poor electrical conductors or insulators.
3. Describe the difference between metals and non-metals regarding malleability and ductility.
Metals are typically malleable (can be hammered into shape) and ductile (can be drawn into wires), while non-metals are usually brittle when solid.
4. How do the melting and boiling points of metals generally compare to those of non-metals?
Metals generally have high melting and boiling points, whereas non-metals typically have lower melting and boiling points.
5. Describe the general chemical property of metals when they react with dilute acids.
Metals generally react with dilute acids to produce a salt and hydrogen gas.
6. Describe the general chemical property of metals regarding their reactions with cold water and steam.
Many metals react with cold water to form a metal hydroxide and hydrogen, or with steam to form a metal oxide and hydrogen.
7. What is the general chemical property of metals when they react with oxygen?
Metals react with oxygen to form metal oxides.
9.2 Uses of metals
8. Why is aluminium used in the manufacture of aircraft?
Aluminium is used because of its low density.
9. State two properties of aluminium that make it suitable for overhead electrical cables.
Its low density and its good electrical conductivity.
10. Why is aluminium used for food containers?
Because of its resistance to corrosion.
11. List two physical properties of copper that make it ideal for electrical wiring.
Its good electrical conductivity and its ductility.
9.3 Alloys and their properties
12. Define an alloy.
An alloy is a mixture of a metal with other elements.
13. What elements are mixed to form the alloy brass?
Copper and zinc.
14. What elements are typically found in the mixture known as stainless steel?
Iron and other elements such as chromium, nickel, and carbon.
15. How do the hardness and strength of alloys compare to those of pure metals?
Alloys can be harder and stronger than pure metals, which often makes them more useful.
16. Describe a use of stainless steel and the properties that make it suitable for that use.
Stainless steel is used in cutlery because of its hardness and its resistance to rusting.
17. How can alloys be identified in a scientific context?
They can be identified from diagrams representing their structure.
18. Explain in terms of structure why alloys are harder and stronger than pure metals.
The different sized atoms in alloys mean the layers of atoms can no longer slide over each other easily.
9.4 Reactivity series
19. List the metals and non-metals in the reactivity series in order from most reactive to least reactive.
Potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, and gold.
20. Describe the reaction, if any, of potassium, sodium, and calcium with cold water.
These metals react vigorously with cold water to produce a metal hydroxide and hydrogen gas.
21. Describe the reaction between magnesium and steam.
Magnesium reacts with steam to produce magnesium oxide and hydrogen gas.
22. Which metals from the reactivity series react with dilute hydrochloric acid?
Magnesium, zinc, and iron react with dilute hydrochloric acid, whereas copper, silver, and gold do not react with it.
23. How are the reactions of metals with water and acids explained?
They are explained in terms of the position of the metals in the reactivity series.
24. How can an order of reactivity be determined experimentally?
It can be deduced from a given set of experimental results, such as observing the speed of reaction or displacement.
25. Describe the relative reactivities of metals in terms of ion formation.
Reactivity is described in terms of the tendency of a metal to form positive ions.
26. How can displacement reactions be used to determine the relative reactivity of metals?
By observing if a metal can displace the aqueous ions of another metal, specifically magnesium, zinc, iron, copper, and silver.
27. Explain the apparent unreactivity of aluminium despite its high position in the reactivity series.
Its apparent unreactivity is due to the presence of a tough, protective oxide layer on its surface.
9.5 Corrosion of metals
28. State the two conditions required for the rusting of iron and steel.
The presence of both oxygen and water.
29. What is the chemical name for the product formed when iron rusts?
Hydrated iron(III) oxide.
30. List three common barrier methods used to prevent the rusting of iron.
Painting, greasing, and coating with plastic.
31. How do barrier methods prevent iron from rusting?
They prevent rusting by excluding oxygen or water from reaching the metal surface.
32. Describe the use of zinc in preventing the corrosion of iron.
Zinc is used in galvanising, which serves as both a barrier method and a form of sacrificial protection.
33. Explain sacrificial protection in terms of the reactivity series.
A more reactive metal (the "sacrificial" metal) is attached to the iron and reacts in preference to it.
34. Explain sacrificial protection in terms of electron loss.
The more reactive metal loses electrons more easily than the iron, thereby protecting the iron from oxidation.
9.6 Extraction of metals
35. How does a metal's position in the reactivity series relate to the ease of obtaining it from its ore?
Metals lower in the reactivity series are easier to obtain from their ores than those higher up.
36. What is the name of the iron ore used in a blast furnace?
Hematite.
37. Describe the initial stage of iron extraction in the blast furnace involving coke.
Carbon (coke) is burned to provide heat and to produce carbon dioxide.
38. How is carbon monoxide produced in the blast furnace?
Carbon dioxide is reduced by more hot coke to form carbon monoxide.
39. Describe the reduction of the iron ore in the blast furnace.
Iron(III) oxide is reduced by carbon monoxide to form molten iron.
40. What is the purpose of adding limestone (calcium carbonate) to the blast furnace?
It undergoes thermal decomposition to produce calcium oxide, which reacts with impurities.
41. How is slag formed in the blast furnace?
Calcium oxide reacts with silica (silicon dioxide) impurities in the ore to form slag (calcium silicate).
42. State the symbol equation for the burning of coke in the blast furnace.
C + O2 → CO2
43. State the symbol equation for the reduction of carbon dioxide to carbon monoxide.
C + CO2 → 2CO
44. State the symbol equation for the reduction of iron(III) oxide by carbon monoxide.
Fe2O3 + 3CO → 2Fe + 3CO2
45. State the symbol equation for the thermal decomposition of limestone.
CaCO3 → CaO + CO2
46. State the symbol equation for the formation of slag.
CaO + SiO2 → CaSiO3
47. What is the main ore of aluminium?
Bauxite.
48. By what method is aluminium extracted from its ore?
Electrolysis.
49. What is the role of cryolite in the extraction of aluminium?
Cryolite is used to dissolve the aluminium oxide, lowering the melting point and increasing conductivity.
50. Why do the carbon anodes need to be regularly replaced during aluminium extraction?
The oxygen produced at the anodes reacts with the carbon at high temperatures to form carbon dioxide, gradually burning them away.
51. Describe the chemical reactions at the electrodes during the electrolysis of aluminium oxide.
At the cathode, aluminium ions gain electrons to form aluminium metal; at the anode, oxide ions lose electrons to form oxygen gas.