properties of materials (topic 10)

Question 1

Answer 1

Question 2

the outer skin of the surfboard is often made from a composite material made from glass fibres surrounded by a polyester, suggest two reasons why an outer skin is added to the poly(styrene) core (2)

Answer 2

• harder
• stronger
• waterproof

Question 3

explain why the polyester coating melts when heated (2)

Answer 3

• thermosoftening
• has no cross-links

Question 4

some polymers do not melt when heated, describe the difference between these polymers and those that melt when heated (2)

Answer 4

• thermosoftening polymers melt when heated because they have no cross-links between polymer chains
• thermosetting polymers have strong cross-links between polymer chains which do not melt when heated

Question 5

state the name of the process that causes iron to corrode

Answer 5

rusting

Question 6

a group of students are discussing the conditions required for an iron nail to rust, plan an investigation to test the predictions of the students (5)

Answer 6

• place one nail in each of three test tubes
• in test tube 1, add a spatula of drying agent and seal with a stopper
• in test tube 2, partially submerge the nail with water and then add the stopper
• in test tube 3, submerge the nail with water, add a layer of oil, and seal with the stopper
• leave for a week and then observe any changes

Question 7

give two reasons why saucepans are made of stainless steel rather than iron (2)

Answer 7

• stainless steel does not rust
• stainless steel is stronger or harder

Question 8

write a word equation for the rusting of iron to form hydrated iron oxide

Answer 8

iron + oxygen + water → hydrated iron oxide

Question 9

explain why covering iron with paint or grease prevents the iron from rusting (2)

Answer 9

• iron needs both oxygen and water to rust
• paint prevents oxygen getting to the iron

Question 10

explain how the zinc covering prevents the iron from rusting (2)

Answer 10

• zinc is more reactive than iron
• zinc reacts with oxygen and water instead of the iron
• iron is galvanised or reacted zinc has sacrificial protection

Question 11

draw the ethene monomer used to create both LDPE and HDPE, low density poly(ethene) and high density poly(ethene)

Answer 11

Question 12

state the name of the polymers that do not melt when heated

Answer 12

thermosetting polymers

Question 13

explain why the structure of these polymers allows them to remain rigid (2)

Answer 13

• polymers have strong cross-links between polymer chains
• cross-links do not break when heated

Question 14

the student is eating hot food, explain, with reference to structure, which one is more suitable for making disposable cutlery (3)

Answer 14

• polymer A is thermosoftening
• (when in contact with hot food) polymer A will melt and deform
• polymer B is thermosetting
• polymer B will remain rigid when hot
• polymer B is the better choice for the cutlery

Question 15

draw the monomer that is used to produce this polymer

Answer 15