Metals and Extraction

1. Steel is an alloy of iron and ____.

• carboncorrect
• zinc
• tin
• copper

Adding a small amount of carbon to iron makes steel, which is harder and stronger than pure iron.

2. What is an alloy?

• A mixture of a metal with one or more other elementscorrect
• A metal that has been melted and cooled
• A very pure single metal
• A metal dissolved in acid

An alloy is a mixture of a metal with one or more other elements, usually made to improve its properties.

3. A shape-memory alloy such as Nitinol can be bent out of shape and then return to its original shape when it is heated.

Answer: True

Heating a shape-memory alloy triggers a change back to its remembered crystal structure, so it returns to its original shape.

4. Match each alloy to the elements it is made from.

Answer: Steel = Iron and carbon; Brass = Copper and zinc; Bronze = Copper and tin; Solder = Tin and lead

Steel is iron and carbon, brass is copper and zinc, bronze is copper and tin, and solder is tin and lead.

5. Three of these are forms of iron or steel. Which is the odd one out?

• Bronzecorrect
• Cast iron
• Mild steel
• High-carbon steel

Cast iron, mild steel and high-carbon steel are all iron-based, but bronze is an alloy of copper and tin.

6. Cast iron contains far more carbon than steel. Roughly what percentage of carbon does cast iron contain?

Answer: 3 %

Cast iron typically contains about 2 to 4 percent carbon, which makes it hard but brittle.

7. 🔩 This iron nail has gone rusty. Rusting of iron needs oxygen and which other substance?

• Watercorrect
• Nitrogen
• Carbon dioxide
• Oil

Iron only rusts when both water and oxygen are present, which is why keeping iron dry stops rust.

8. Select ALL the methods that help prevent iron from rusting.

• Painting the surfacecorrect
• Oiling or greasing itcorrect
• Galvanising with zinccorrect
• Spraying it with salt water

Painting, oiling and galvanising all keep out water and air, while spraying with salt water would speed rusting up.

9. Salty water makes iron rust faster than pure water does.

Answer: True

Dissolved salt speeds up the electrochemical reactions of rusting, which is why cars rust quickly near the sea.

10. Coating iron with a protective layer of zinc to stop it rusting is called ____.

• galvanisingcorrect
• electrolysis
• smelting
• annealing

Galvanising covers iron with zinc, which both keeps out water and air and protects the iron sacrificially.

11. In sacrificial protection, a block of a more reactive metal such as zinc is attached to iron so that it does what?

• Corrodes instead of the ironcorrect
• Makes the iron more reactive
• Turns the iron into an alloy
• Adds extra oxygen to the iron

The more reactive metal corrodes in place of the iron, protecting it until the block is used up and replaced.

12. Recall the electrochemical steps of iron rusting in the correct order.

Answer: Iron loses electrons: Fe -> Fe2+ + 2e- -> Oxygen and water gain electrons: O2 + 2H2O + 4e- -> 4OH- -> Fe2+ is oxidised further to Fe3+ -> Fe3+ forms hydrated iron(III) oxide (rust)

Iron is oxidised to Fe2+ at anodic regions, oxygen and water are reduced at cathodic regions, Fe2+ is oxidised to Fe3+, and hydrated iron(III) oxide forms.

13. Metals less reactive than carbon, such as iron, can be extracted by reduction with ____.

• carboncorrect
• electricity
• hydrogen
• water

Carbon is cheap and can remove oxygen from the oxides of less reactive metals like iron in a blast furnace.

14. Build the sentence describing what carbon does in the blast furnace.

Answer: Carbon reduces iron oxide to iron

Carbon (as carbon monoxide) reduces iron oxide to iron by removing its oxygen.

15. Match each metal to how it is usually extracted.

Answer: Aluminium = Electrolysis of molten ore; Iron = Reduction with carbon; Gold = Found native in the ground; Zinc = Roasting the ore, then reduction

Reactive metals like aluminium need electrolysis, iron is reduced by carbon, gold is found native, and zinc is roasted and reduced.

16. Which statements about slag formation in the blast furnace are correct?

• Limestone decomposes: CaCO3 -> CaO + CO2correct
• Calcium oxide reacts with sand: CaO + SiO2 -> CaSiO3correct
• Molten slag floats on the denser iron and is tapped off separatelycorrect
• Slag is the main iron product sold from the furnace

Limestone decomposes to CaO, which neutralises acidic silica to molten calcium silicate slag that floats on the denser iron.

17. Because delta G for oxide formation becomes less negative at high temperature, unstable oxides such as silver oxide and mercury(II) oxide decompose back to the metal on simple heating.

Answer: True

For these unreactive metals the oxide-formation line lies high on the Ellingham diagram, so heating alone makes the oxide unstable and it decomposes to the metal.

18. Roughly what percentage of the energy needed to make steel from iron ore is SAVED by recycling scrap steel in an electric arc furnace?

Answer: 75 %

Recycling steel typically uses only about a quarter of the energy of primary production, saving roughly 70-75 percent.

19. Copper is more reactive than potassium.

Answer: False

This is false: potassium is near the top of the reactivity series while copper is near the bottom.

20. When a metal reacts with oxygen it forms a metal ____.

• oxidecorrect
• hydroxide
• carbonate
• chloride

Metals react with oxygen to form oxides, for example magnesium burns to form magnesium oxide.

21. Complete the word equation: zinc + hydrochloric acid gives...

Answer: zinc chloride + hydrogen

Zinc reacts with hydrochloric acid to make the salt zinc chloride plus hydrogen gas.

22. Select ALL correct statements about standard electrode potentials.

• They are measured relative to the standard hydrogen electrode, defined as 0 V
• A more positive value means the species is more easily reducedcorrect
• Standard conditions include 298 K and 1 mol/dm3 solutionscorrect
• The metal with the most negative value is the strongest oxidising agent

Electrode potentials are measured against the standard hydrogen electrode (0 V) under standard conditions; a more positive value means the species is more easily reduced, and the most negative value belongs to the strongest reducing (not oxidising) agent.

23. In the half-equation Al -> Al(3+) + n e-, what is the value of n?

Answer: 3 electrons

Aluminium loses three electrons to form the Al3+ ion, so n = 3.

24. Match each group 2 metal to the colour it gives in a flame test.

Answer: Calcium = Brick-red; Strontium = Crimson; Barium = Apple-green; Magnesium = No flame colour

Calcium gives a brick-red flame, strontium crimson, and barium apple-green, while magnesium gives no characteristic flame colour.

25. A metal that can be pulled out into a thin wire is described as ____.

• ductilecorrect
• malleable
• sonorous
• brittle

Ductile means a material can be drawn into wires, which is why copper is used for electrical cables.

26. Select ALL the statements that are typical properties of most metals.

• They are malleablecorrect
• They conduct electricity wellcorrect
• They usually have a high densitycorrect
• They all have very low melting points

Most metals are malleable, conduct electricity well and have high densities, but they usually have high (not low) melting points.

27. Mercury is the only metal that is a liquid at room temperature.

Answer: True

Mercury is unusual because it stays liquid at room temperature; all other common metals are solids.

28. Match each property of metals to what it means.

Answer: Malleable = Can be hammered into shape; Ductile = Can be drawn into wires; Sonorous = Rings when struck; Lustrous = Has a shiny surface

Malleable means it can be shaped, ductile means it can be drawn into wire, sonorous means it rings when struck, and lustrous means it is shiny.

29. Why are metals good conductors of electricity?

• They have free electrons that can move and carry chargecorrect
• Their atoms are held together very loosely
• They contain positively charged protons that flow
• They are made of tiny magnets

Metals contain delocalised (free) electrons that are able to move through the structure and carry charge.

30. Metals generally have high melting points. Roughly what temperature does iron melt at?

Answer: 1538 degrees C

Iron melts at about 1538 degrees Celsius, a very high melting point caused by strong metallic bonding.