C15: Using our resources

Question 1

What is corrosion?

Answer 1

The destruction of materials by chemical reactions with substances in the environment.

Question 2

What is rusting?

Answer 2

An example of corrosion.
Only applies to iron and its alloys (e.g. steel).

Question 3

What is the experiment for rusting?

Answer 3

Take 3 test tubes and place an iron nail in each. In one, place water, in another place distilled water (boiled to remove any air) with oil (which will sit on top) and in the last one, place anhydrous calcium chloride powder and a rubber bung. Leave for 3 days and observe.

Question 4

How can corrosion be stopped?

Answer 4

Use a barrier, e.g. grease, paint or electroplating.
Or coat a metal with a more reactive metal (galvanising).

Question 5

What is galvanising?

Answer 5

Coating a less reactive metal with a more reactive one, acting as a barrier between iron and air/water. If zinc gets scratched, it still acts as a barrier as zinc will corrode instead of iron because zinc is more reactive - sacrificial protection.

Question 6

What is an alloy?

Answer 6

Contains a metal blended with other elements. It is a mixture.

Question 7

How is an alloy made?

Answer 7

Mixing in other elements, then allowing the alloy to cool.

Question 8

What are 2 alloys of copper?

Answer 8

Bronze - copper + tin - hard and tends not to corrode, so is used for statues.
Brass - copper + zinc - harder than pure copper, but can be formed into different shapes. Used for door handles and musical instruments.

Question 9

What are the alloys of gold?

Answer 9

Usually alloyed with silver, copper and zinc to make it harder since pure gold is too soft.

Question 10

What are steels?

Answer 10

Alloys of iron containing specific amounts of the non-metal carbon. Steel also contains other metals.
High carbon steels - extremely hard and brittle. Tend to break when hit with a hammer. Used to make cutting tools e.g. chisels.
Low carbon steels - softer and shaped easily, used to make car bodies.
Stainless steel - contains chromium and nickel, which makes it more resistant to corrosion.

Question 11

What are the uses of alloys of aluminium?

Answer 11

Low density - used to make aeroplane bodies.

Question 12

What are ceramics?

Question 13

What is soda-lime glass?

Answer 13

Most of the glass that we use.
Ideal for things like windows and bottles. Mix together sand, sodium carbonate and limestone. Heat in a furnace until it melts. When it cools, it solidifies into the shape that we want.

Question 14

What is the problem with soda-lime glass?

Answer 14

Low melting point - limits its uses

Question 15

What is borosilicate glass?

Answer 15

Higher melting point than soda-lime glass. Useful for objects that require heating e.g. kitchenware and labware.
Made by melting a mixture of sand a boron trioxide.

Question 16

What are clay ceramics?

Answer 16

e.g. pottery and bricks.
Clay is a mineral found in the ground. When it’s wet, it can be shaped, then heated into a furnace to harden.

Question 17

What are composites?

Answer 17

Made by combining two different materials.
Reinforcement - consists of fibres or fragments of one material, this is surrounded by a matrix or binder material. e.g. reinforced concrete - steel bars surrounded by concrete, extremely strong and used to make buildings.

Question 18

What do the properties of polymers depend on?

Answer 18

The monomer and the conditions used to make the polymer.

Question 19

What conditions can we change to change the properties of a polymer?

Answer 19

Change the reaction temperature, reaction pressure or the catalyst.

Question 20

What are thermosoftening polymers?

Answer 20

Polymers which melt when heated. They can be reshaped when soft and go back to a solid when cooled down.
They contain intermolecular forces, which can be broken using heat. When cooled, the forces reform and polymer goes back to being a solid.

Question 21

What are thermosetting polymers?

Answer 21

Do not melt when heated.
Contain strong cross-links. Not broken by heat, so do not melt when heated.

Question 22

What is the use of ammonia?

Answer 22

To make nitrogen-based fertilisers for farming.

Question 23

What is the equation for the Haber process?

Answer 23

N2(g) +3H2(g) <=> 2NH3 (g)
iron catalyst

Question 24

What is the source of the raw materials in the production of ammonia?

Answer 24

Nitrogen - extracted from the air
Hydrogen - produced by reacting methane with steam.

Question 25

What are the conditions required for the Haber process?

Answer 25

Iron catalyst
200 atm
450C

Question 26

How is the yield of ammonia increased?

Answer 26

Cool ammonia - turns it into a liquid which can be removed.

Question 27

What happens to unreacted nitrogen and hydrogen in Haber process?

Answer 27

Recycled back over the catalyst.

Question 28

Why are the conditions for producing ammonia chosen?

Answer 28

High temp - shifts position of equilibrium to the left side because forward reaction is exothermic. A cool temperature makes reaction slow, so choose 450C as a compromise temperature.
Pressure - high pressure makes more ammonia as position of equilibrium moves to the side with less moles (right side).

Question 29

What effect does a catalyst have on the position of equilibrium?

Answer 29

No effect

Question 30

Why are fertilisers critical for modern farming?

Answer 30

Replace the elements which have been taken up by plants.

Question 31

Where are NPK fertilisers produced?

Answer 31

Large industrial facilities. A variety of different raw materials are processed together to produce the exact fertiliser required. They are formulations of different salts.

Question 32

What is the main compound of nitrogen in NPK fertilisers?

Answer 32

Ammonium Nitrate, to make this, ammonia is made by the Haber process. This ammonia can be used to produce nitric acid. React these to make ammonium nitrate.

Question 33

Where does the potassium in NPK fertilisers come from?

Answer 33

Potassium chloride/ potassium sulphate - mined from the ground, used directly without further processing.

Question 34

Where does the phosphorus from NPK fertilisers come from?

Answer 34

Phosphate frock mined from the ground - has to be chemically processed before being used in fertilisers.

Question 35

Describe the process of treating phosphate rock with nitric acid.

Answer 35

Treating the rock with nitric acid and produces phosphoric acid and calcium nitrate. Phosphoric acid is neutralised with ammonia, producing ammonium phosphate, which can be used in NPK fertiliser.
If we treat it with sulfuric acid, then a mixture of calcium phosphate and calcium sulphate is made, called single superphosphate.
If phosphoric acid used, then triple superphosphate is produced, which can be found in NPK fertilisers.