C15.1 - C15.5 - Using Our Recources (Set B)✔️

Question 1

What causes corrosion? What effect can it have on the metal?

Answer 1

Caused by chemical reactions between metal and substances in the enviorment - the products of corrosion can affect the strength of a metal an its apperance and can lead to it being destroyed

Question 2

What is rusting?

Answer 2

The corrosion of iron which results in rust forming on the surface of the iron (and most steels) - which can brush of - exposing fresh iron which then rusts and continues until the iron is completley destroyed

Question 3

How is aluminium protected from corrosion?

Answer 3

Has a protectie oxide layer which protects the aluminium beneath it from further corrosion

Question 4

4 ways rusting can be prevented on iron and steel?

Answer 4

• coating iron or steel in paint
• coating in oil and greese
• coating in plastic
• coating it with a less reactive metal or more reactive metal

Question 5

Issues with covering iron and steel in a protective layer?

Answer 5

Once the barrier is even slightly scratched or damaged it will start rusting which spreads under the coating

Question 6

Explain fully how iron being galvanised protects it from rusting?

Answer 6

Zinc is more reactive than the iron and a stronger reducing agent so it has a higher tendency to form positive ions by giving away electrons - zinc atoms loose electrons and become oxidised therefore any water or oxygen reacts with zinc rather than the iron - refered to a sacrifical protection

Question 7

Two methods for preventing rusting of iron and steel?

Answer 7

• using a metal coating - so the metal is galvanised
• using a protective barrier eg paint/plastic

Question 8

Explain sacrifical protection?

Answer 8

The process of using another metal to protect iron or steel from rusting - magnesium, aluminium or zinc are often used - this method is mainly used under harsh conditions like when iron is in contact with seawater (which would accelerate rusting) or when it is likley to be scratched

Question 9

Equation for rusting?

Answer 9

Iron + oxygen + water → hydrated iron (III) oxide

Question 10

What is the chemical name for rust?

Answer 10

Hydrated iron (III) oxide - has water loosley bonded in its structure

Question 11

Why are alloys harder then pure metal? Refer to their structure?

Answer 11

The layers are harder to slide because they are jammed in position as the metal ions are different sizes

Question 12

What is bronze?

Answer 12

An alloy of copper and tin - tough and resistant to corrosion

Question 13

What is brass?

Answer 13

Alloy of copper and zinc - a lot harder than copper but can be hammered into sheets

Question 14

What does the alloy gold normaly consist of?

Answer 14

Silver, copper an zinc - the proportion of gold in the alloy is measured in carats with 24 carat being 100% (pure gold) and 18 carrat being (75% gold) - often used to make jewellery

Question 15

What are steels?

Answer 15

Alloys of iron that contain specific amounts of carbon and other metals - some steel contain chromium and nickel and are hard and resistant to corrosion

Question 16

Difference in carbon levels in steel?Explain features?

Answer 16

high carbon steel is strong but brittle and low carbon steel is softer and more easily shaped

Question 17

Example of the uses of copper alloys?

Answer 17

• statues and decorative items
• ship propellers

Question 18

Example of the uses of brass alloys?

Answer 18

• used to make musical instruments
• door fittings and taps

Question 19

Example of the uses of aluminium alloys?

Answer 19

• used to build aircraft
• armour plating on tanks and military vehicles

Question 20

Example of the uses of gold alloys?

Answer 20

• jewellery

Question 21

Example of the uses of carbon steel?

Answer 21

• making cars
• making ships
• building structures

Question 22

Example of the uses of nickel-steel

Answer 22

• make long-span bridges
• military plating on vehicles

Question 23

What are stainless steels?

Answer 23

Steels that contain a higher percentage of other metals and are even more expensive

Question 24

Uses of stainless steels? Why are they used for this?

Answer 24

Used in the chemical industry to make reaction vessels and pipework which is often expensive to set up but can withstands high temperatures and pressure as well as corrosive chemicals

Question 25

Three examples of steels?

Answer 25

• high carbon steel - hard but brittle
• low carbon steels - softer and easily shaped
• stainless steel - resistant to corrosion

Question 26

What are two thing the properties of a polymer depend on?

Answer 26

-the monomers used to make it

-the conditions chosen to carry out the reaction

Question 27

What are thermosofening polymers? Explain their features?

Answer 27

Made up of individual polymer chains that are tangled together and are relativley easy to seperate - will soften quite easily when heated an then will re-set and cool down

Question 28

What are thermosetting polymers? Explain their features?

Answer 28

Polymers which do not melt when we heat then - they have strong convalent bond froming cross -links between their polymer chains

Question 29

Explain fully what happens when a thermosoftening polymer is heated? Refer to structure?

Answer 29

The forces between the polymer chains are weak - when heated the weak intermolecular forces are broken - the polymer becomes soft once it cools down the intermolecular forces bring the polymer molecules back together and the polymer hardens - this type of polymer can be remoulded

Question 30

Explain fully what happens when a thermosetting polymer is heated? Refer to structure?

Answer 30

Their monomers make convalent bonds between the polymer chains when they are first heated in order to shape them - these convalent bonds are strong and stop the polymer from softening - the convalent cross-links between chains do not allow them to seperate even if heated strongly - the polymer will char at high enough temperatures

Question 31

What happens to a thermosetting polymer if heated enough?

Answer 31

Will not soften but will char at high enough temperatures

Question 32

What is soda glass? What does it consit of?

Answer 32

Most of the glass we use is soda-lime glass, made by heating a mixture of sand, sodium carbonate and limestone

Question 33

What is borosilicate glass? What does it consit of?

Answer 33

made from sand and boron trioxide, melts at higher temperatures than soda-lime glass.

Question 34

What are clay ceramics?

Answer 34

Include pottery and bricks and are made by shaping wet clay and then heating in a furnace

Question 35

What are composites?

Answer 35

Usually made of two materials, with one material acting as a binder for the other material - improving a desirable property that could not be offered by the origional material alone

Question 36

Example of two composites?

Answer 36

• plywood - which is made of thin sheets of wood glued together, with the grain in successive layers
• concrete - made from cement, sand and gravel mixed with water - reinforced with metal rods

Question 37

How is low density (LD) poly(ethene) formed?

Answer 37

Using high pressure and a trace of oxygen - the polymer chains are randomly branched and cannot pack closely hence the LD

Question 38

How is high density (HD) poly(ethene) formed?

Answer 38

Using a catalyst at 50 degrees and a slighly raised pressure - HD poly ethene is made up of straighter poly(ethene) chains which can pack more closley together hence the HD