Student worksheet

Raw materials

Iron and aluminium are very common substances in the Earth’s crust. They are in the form of compounds often called minerals and can be part of rock crystals.

Iron-rich soils, like the soils in central Australia, are red in colour. While iron and aluminium are significant components of the Earth’s crust, processing it requires high concentrations. High concentrations of iron compounds are called iron ore. In Australia, the high concentrations of aluminium compounds are in minerals called bauxite.

These minerals are extracted from vast open-cut mines. They must be transported to the coast, where they are loaded onto bulk carriers (type of ship) and shipped to a port where the mineral will be processed into metal.

i. Use the internet to find:

Go to the website http://www.infomine.com/investment/metal-prices/. This website provides graphs of the price fluctuations for the more expensive metals. These are the metals after they have been processed. The measurement is in US dollars for one pound weight. A pound is 0.454kg. Of the 16 graphs, coal and iron are not displayed.

ii. Which of the metals is the most expensive? What is the metal’s symbol?

iii. Which of the metals is the least expensive? What is the metal’s symbol?

iv. Which metal changes its price the most? What is the metal’s symbol?

In a process that takes in the order of 100 million years, liquid and gas, hydrocarbons have accumulated in pockets inside the Earth’s crust. They are mixed in with the surrounding minerals, but can’t escape upwards as there is a cap of rock they can’t get through.

We give these hydrocarbons a general name called oil and gas. This oil and gas is extracted by drilling oil wells. These hydrocarbons from oil wells can have very different combinations of hydrocarbon compounds. The simplest hydrocarbon is methane. Its chemical formula is CH₄. This is a gas and is commercially called natural gas. It is the gas we use for cooking and heating.

Some of the other hydrocarbons, such as propane, are a gas when released into the atmosphere. The other hydrocarbons are liquid. The oil from oil wells is refined in a refinery. The refinery produces hydrocarbons for specific needs such as petrol, kerosene, diesel and engine oil. Oil wells that have very large hydrocarbons will be used to make the tar that seals roads. The refining process produces hydrocarbons such as ethylene that can be used to make plastics.

Most coastal capital cities have one or more oil refineries or large oil storage facilities. Locate an oil refinery. First, use Google Images and use appropriate words such as ‘Australian oil refinery’ to search for what an oil refinery looks like. Once an oil refinery has been found, use Google Maps and click on satellite.

v. Describe some of the structures that can be observed in an oil refinery.

Watch Video 7. Video on manufacturing materials

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vi. How are raw materials used for manufacturing?

Refining iron ore

To produce iron from iron ore two chemical reactions are required inside a blast furnace operating at 2000^oC. The raw materials required to produce iron is iron ore and coke. Oxygen is needed as part of the reaction. Limestone or another chemical is added to remove the bulk of the impurities. Coke is a form of processed coal. Coke is light and porous containing a lot of air and able to burn at very high temperatures. Australia is a major exporter of both iron ore and coke which also called coking coal.

The two chemical reactions are:

2C + O₂ → 2CO and

Fe₂O₃ + 3CO → 2Fe + 3CO₂

In the first reaction the coke (C) combines with oxygen (O₂) to produce carbon monoxide (CO)

The carbon monoxide at 2000^oC reduces the iron oxide to iron.

Where does the carbon come from for the chemical reaction?

2. What chemical is required to react with Fe₂O₃ to produce Fe (iron)?

3. Under what conditions will CO (carbon monoxide) react with Fe₂O₃?

4. Suggest a chemical equation for iron forming rust. Hint: how would Fe react with both oxygen and water? (The chemical formula for rust is FeO(OH)·Fe(OH)₃)

5. Use the periodic table to find out more about Fe, O and C. Place the elements into the correct space in the blank periodic table.

Refining bauxite

The temperature required to produce aluminium from bauxite in a normal furnace is far too high to be practical. To produce aluminium from bauxite there are two major steps, refining and smelting.

Step 1: Refining

The chemical formula for bauxite is (AlO_x(OH)_3–2x). The first part of the process removes all the impurities that are mined with the bauxite and produces alumina (Al₂O₃). Sodium hydroxide (NaOH), heat and pressure are required to go through a number of chemical reactions to separate the mixture of chemicals into pure Al₂O₃. This looks like a white powder. At the end of the process the Sodium hydroxide (NaOH) can be reused after some of the impurities are removed.

In a formula leaving out the middle steps

AlO_x(OH)_3–2x + 2 NaOH = Al₂O₃ + 2 NaOH + water (H₂O)

Step 2: Smelting

Electricity is used to turn the alumina (Al₂O₃) into aluminium (Al). First the alumina (Al₂O₃) is dissolved inside a reduction cell. Electricity is passed through the solution. The reduction cells operate at about 900^oC.

At the cathode, the aluminium ions combine with electrons to produce molten Aluminium.

Al³⁺ + 3e⁻ → Al

At the anode, oxygen is formed when each atom gives off two electrons.

2O²⁻ → O₂ + 4e⁻

Look up this website that show the refining and smelting process.

When refining bauxite (AlO_x(OH)_3–2x) to make alumina (Al₂O₃) what happens to the Sodium hydroxide (NaOH)?

2. What other products are produced besides alumina.

3. How is smelting alumina different to smelting iron ore? What is the source of energy used in aluminium smelting?

4. Make a simplified diagram of how aluminium is smelted. In the diagram:

Describe all the material being produced by the chemical formulas.
Describe the alumina going the furnace (the furnace is called a pot).
Draw an anode and a cathode.
Show the products that are produced.
Write the chemical reaction for alumina to become aluminium.

Over 70% of all aluminium ever produced is still being used.

Use the website and look at the aluminium cycle.

5. Why is aluminium one of the world’s ultimate recycle materials?

6. Use the periodic table to find out more about Al, O, Na and H. Place the chemicals into the correct space in the blank periodic table.

Producing plastics

80 million tonnes of polyethylene is made worldwide every year. Polyethylene is made from the hydrocarbon ethylene which is a gas under normal conditions. The chemical formula for ethylene is C₂H_4.Ethylene is usually produced by the petrochemical industry, but can also be made from ethanol.

Polyethylene is a long chain made from ethylene molecules. The formula for most types of polyethylene is (C₂H₄)_nH_2. A catalyst is used to produce the chemical reaction. During the chemical reaction a lot of heat is produced. There are many types of polyethylene. The length of the molecule and the way the chains are organised, tangled or cross bonded produces plastics with different properties.

Draw an image of ethylene:

2. Describe the structure of the ethylene molecule and some of its properties.

3. Using half an A4 page draw an ethylene molecule. Now as a class use sticky tape to join all the ethylene molecules together to produce a long chain. Use a thick marker to mark any changed bonds between the atoms.

4. In the polyethylene molecule, which atoms are bonded together to make the chain?

5. Draw an image of polyethylene:

6. Use an image search engine and type polyethylene. Look at the products.

What kind of products are made from polyethylene?

7. Watch the YouTube video

How Poly Bags Are Made - LK Packaging (https://www.youtube.com/watch?v=O7BLsexJn0c)

While watching the video try to identify what processes are used to produce plastic resin. Once the plastic resin is produced, are there any further chemical reactions required in its production?

* https://en.wikipedia.org/wiki/Iron#Industrialproduction

These Planet Ark resources were developed by Cool.org with funding from the Alcoa Foundation.

National Recycling Week - Manufacturing Materials

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