C2 - Material Choices

Question 1

How big is a nanometre?

Answer 1

1.0^-9 of a metre or 1.0-6 mm

Question 2

How is a crystalline polymer different?

Answer 2

Its chains are closely packaged together.

Question 3

Why must you keep all factors except one variable factor constant in an experiment?

Answer 3

• To keep it a fair test.
• Another factor could influence the result.
• The factor will not be the only one that can affect the outcome/no longer able to compare results.

Question 4

Discuss the risks of using plasticisers, and why people may view these risks differently.

Answer 4

Risks

• Harm young children, who may use materials which contain plasticisers in toys.
• Our bodies do not decompose them/they accumulate in tissue.
• Plasticisers could leach out of PVC and into food, the environment or human tissue.
• Plasticisers known to cause harm to rats.

Views

• Evidence linking them with cancer. Some argue that they have been used for over half a century and no known cases of harm are known.
• Insufficient evidence/no causal mechanism.
• Biased views from plastic manufacturers/public pressure groups.
• Plasticiser concentrations in humans/environment are very low/below EU limits.
• Some people may perceive the risk higher than it actually is.
• Some people may think the benefit outweighs the risk, but others think the opposite.
• Data on harmful effects is inconclusive.
• Data from animals may not indicate what is true for humans.
• Using plasticisers has benefits with examples.
• Most people do not know enough to be worried.
• Manufacturers/scientists have vested interests.

Question 5

Why do we use rock salt to treat icy roads?

Answer 5

It melts the ice by lowering the melting point.

Question 6

Why do we not use rock salt in the food industry?

Answer 6

It may contain impurities.

Question 7

Describe how salt is obtained by solution mining.

Answer 7

Water is pumped underground and into the salt deposit.

Salt dissolves in the water, forming a concentrated salt solution.

Then, this is pumped up to the surface ready for use.

Question 8

Discuss the environmental issues that can occur as a result of solution mining.

Answer 8

There are gaps underground where the salt was removed. Also, subsidence can occur, causing buildings to sink/sink holes to appear.

Question 9

Give a natural example of where nanoscale particles are used.

Answer 9

In sea spray.

Question 10

Give an accidental example of where nanoscale particles are used.

Answer 10

During the combustion of fuels, particulate carbon can be released.

Question 11

What is it called when nanoscale particles are made deliberately by scientists?

Answer 11

Nanotechnology.

Question 12

Define melting point.

Answer 12

The temperature at which a solid turns into a liquid.

Question 13

Define tensile strength.

Answer 13

The force needed to break a material when it is being stretched.

Question 14

Define compressive strength.

Answer 14

The force needed to crush a material when it is being squeezed.

Question 15

Define stiffness.

Answer 15

The force needed to bend a material.

Question 16

Define hardness.

Answer 16

How well a material stands up to wear. Can be compared by scartching two materials together.

Question 17

Define density.

Answer 17

The mass of a given volume of material. Compares how heavy something is for its size.

Question 18

Give reasons why synthetic materials have replaced natural materials.

Answer 18

• Some natural materials are in short supply.
• They can be designed to give particular properties.
• They are often cheaper and can be made in the quantity needed.

Question 19

What are most hydrocarbons used for?

Answer 19

Fuels (90%).

Question 20

Compare LDPE and HDPE.

Answer 20

LDPE has long chains with branches.

HDPE has long chains but no branches. It is more crystalline, but can be brittle.

Question 21

Thermoplastics can/can not be heated and moulded into shape.

Answer 21

Thermoplastics can be heated and moulded into shape.

Thermosetting plastics can not. They contain cross-links.

Question 22

How are crystalline structures manufactured?

Answer 22

By removing branches on the main polymer chain and making the chains as flat as possible.

Then, the polymers are drawn through a tiny hole when heated, to make the chains line up and set close together, forming a higher tensile strength fibre.

Question 23

Discuss the benefits and risks of using nanoparticles.

Answer 23

Benefits

• They can kill bacteria (Silver nanoparticles).
• Nanoparticles occur naturally, and pose no danger.

Risks

• Silver nanoparticles can be washed out of clothes and into the environment, killing useful bacteria (e.g: In sewers) or microorganisms in the environment.
• Nanoparticles are small enough to pass through skin into blood, and into body organs. The possible medical effects of this are not yet known.
• Little research has been carried out onto the harmful effects of nanoparticles.
• A fear is that nanoparticles in the air might be breathed in and cause lung or brain damage.
• New nanoparticles with new properties have been manufactured.
• No one knows if nanoparticles used in solids can escape into the air.
• Some people want proof.

Question 24

What are the units of density?

Answer 24

g/cm³ or kg/m³.