C15 - Using Our Resources - C15.1, C15.2, C15.3 Done

Question 1

What is corrosion of metals caused by?

Answer 1

Chemical reactions between the metal and other substances in the environment

Question 2

What is rusting?

Answer 2

The corrosion of iron (and most steels)

Question 3

What is the formula for rust and what is needed for its process?

Answer 3

Rust’s formula is Fe2O3, and rusting’s reactants are iron, water and oxygen

Question 4

What is the word equation for the process of rusting?

Answer 4

Iron + Oxygen + Water ===> Hydrated iron(III) oxide

Question 5

What are the two ways to prevent rust forming?

Answer 5

Sacrificial protection - getting a more or less reactive metal to react with the oxygen and water instead of the iron, and barrier protection - whereby the iron is covered by a physical barrier to stop the oxygen and water getting to it

Question 6

How does sacrificial protection work?

Answer 6

The sacrificial metal is electroplated onto the object, or attached to it through dipping the object into it or through wires. When the oxygen and water are applied, they react with the sacrificial metal as it is easier to react with. One example of sacrificial protection is galvanisation - protecting iron with zinc

Question 7

Where is sacrificial protection often used? (What kind of conditions?)

Answer 7

Sacrificial protection is often used in tough conditions where iron rusts easily, such as by the sea where the iron would be in almost constant contact with the seawater

Question 8

Does the sacrificial metal also forever?

Answer 8

No, it must be replaced after some time as it reacts with the water and oxygen - and so would need replacing afterwards in order to remain the actual metal - not, for example, zinc xyz

Question 9

Why are alloys needed for many pure metals?

Answer 9

As many pure metals such as aluminium and iron are relatively soft and early shaped, due to their lattice ionic structures with layers that can slide over each other. This means that they will just bend when put under pressure, rather than actually resisting

Question 10

What is bronze an alloy of and when was it discovered?

Answer 10

Copper and tin, and it was discovered around 5500 years ago

Question 11

Where is bronze often used, and what qualities mean that it is used there?

Answer 11

In ship’s propellers, and statues and decorative items. This is because it looks good, and is strong and resistant to corrosion

Question 12

What is brass an alloy of?

Answer 12

Copper and zinc

Question 13

Where is brass often used?

Answer 13

In instruments, door fittings and taps

Question 14

What qualities does brass have?

Answer 14

Strong but workable

Question 15

What can the different alloys of aluminium be used for? (From ….. to ….. )

Answer 15

From armour to aircraft, it has lightweight and heavier variants, all of which are strong

Question 16

What is gold often alloyed with when making jewellery?

Answer 16

Copper

Question 17

How is the purity of gold measured?

Answer 17

Through carats, if you divide the number of carats some gold is by 24, then you will get its percentage purity

Question 18

What are carbon steels?

Answer 18

Carbon steels are alloys of iron and carbon (ranging from 0.03% carbon to 4%). They are cheap to make and are strong but brittle in high carbon concentrations, and malleable and weaker in low concentrations

Question 19

Where are carbon steels used?

Answer 19

Car bodies, machinery, ships, containers and structural steel

Question 20

What are stainless steels made of and what properties do they have?

Answer 20

They do not rust, they are strong and they are hard. They are made of iron with high percentages of chromium-nickel

Question 21

What are nickel-steel alloys used for?

Answer 21

Long span bridges, bicycle chains, and military armour plating, as they are very resistant to stretching forces

Question 22

What two factors do the properties of a polymer rely on?

Answer 22

The monomers used to make it, and the conditions chosen to carry out the reaction

Question 23

What is the difference between the structures of high density and low density polymers?

Answer 23

Low density polymers are much more randomly arranged, with branches coming off branches and large and small pockets of space in between them, whereas in contrast high density polymers are more orderly in straight lines

Question 24

What are thermosoftening polymers?

Answer 24

Polymers that melt and soften when they are heated. Their chains are often tangled rather than bonded

Question 25

What are thermosetting polymers?

Answer 25

Polymers that do not melt due to strong covalent bonds the hold their chains together. At high enough temperatures, the polymer will just char rather than melt