Metals from Their Ores: Extraction and Redox

Winning metals from rock

Most metals are locked inside ores in the ground, and how we get them out depends on how reactive they are. The least reactive metals, such as gold, are so unreactive they are found native, sitting in the ground as the pure metal. Metals less reactive than carbon, such as iron, zinc and copper, are extracted by reduction with carbon, where the carbon takes the oxygen away from the metal oxide. Metals more reactive than carbon, such as aluminium, hold onto their oxygen too tightly for carbon and must be extracted using electrolysis. At Higher Tier, oxidation and reduction are explained not just by oxygen but by electrons: oxidation is loss of electrons and reduction is gain, remembered as OIL RIG. This module covers extraction and this redox idea.

Extraction words

Learn these before you match any metal, and keep the position of carbon in the reactivity series in mind.

Reduction with carbon against electrolysis

Two extraction routes suit metals on opposite sides of carbon in the reactivity series.

How to pick an extraction route

Do not guess the method. Place the metal against carbon in the reactivity series first. If the metal is so unreactive it never combined, dig it up as it is. If it sits below carbon, let carbon pull the oxygen off it. If it sits above carbon, only electricity is strong enough, so use electrolysis. Name where the metal falls, then name the route that its position forces, and say why the cheaper option would not work for a reactive metal.

Match the metal to its extraction

Which extraction method?

Aluminium sits above carbon in the reactivity series. Which method must be used to extract it from its ore?

• Electrolysis.
• Reduction with carbon.
• It is dug up native.
• Simply burning the ore in air.

Redox in terms of electrons

Higher Tier. Select the TWO correct statements about oxidation and reduction as electron transfer.

• Oxidation is the loss of electrons
• Reduction is the gain of electrons
• Oxidation is the gain of electrons
• Reduction is the loss of electrons

Electrons gained

In the extraction of aluminium, each aluminium ion Al3+ gains 3 electrons to become an atom. How many electrons are gained in total when 4 aluminium ions become atoms?

Order extracting iron

Put the stages of extracting iron by reduction with carbon in order, earliest first.

• Iron ore, an iron oxide, is dug from the ground
• It is heated strongly with carbon in a furnace
• The carbon removes the oxygen from the iron oxide
• Molten iron is left and runs off

Complete the facts

A metal so unreactive it is found uncombined is said to occur _____. A metal less reactive than carbon is extracted by reduction with _____. A metal more reactive than carbon must be extracted by _____. At Higher Tier, the loss of electrons is called _____.

Match the redox term to its meaning

Spot the true extraction facts

Tap the TWO statements that are true about extracting metals.

• Very unreactive metals such as gold are found native
• Metals more reactive than carbon need electrolysis
• Carbon can reduce every metal, however reactive
• Reduction is the loss of electrons

Choose and explain

Read each case and choose the best response, with a reason.

• A metal sits well below carbon in the reactivity series. Which is the cheapest sensible way to extract it?
• Higher Tier. In a reaction a zinc atom loses two electrons to become a zinc ion. What has happened to the zinc?
• A student says gold must be dug out by electrolysis like aluminium. How should this be corrected?

Explain how metals are extracted

A mining company handles gold, iron and aluminium. Explain how the reactivity of each metal decides the way it is extracted.

• Explain why gold is found native and needs no reduction
• Explain how iron is extracted by reduction with carbon
• Explain why aluminium needs electrolysis instead of carbon
• Use the position of carbon in the reactivity series in your reasoning
• Finish, at Higher Tier, by defining reduction in terms of electrons