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Chemistry 21st century > Material Choices > Flashcards

Material Choices Flashcards

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1
Q

What makes a material suitable for a job?

A

The properties that it has

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2
Q

Name some properties that might be important for the job a material is being used for.

A

Melting point, tensile strength, compressive strength, stiffness, hardness, density

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3
Q

What is the melting point of a material?

A

The temperature at which it turns into a liquid.

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4
Q

What is tensile strength?

A

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

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5
Q

What is compressive strength?

A

The force needed to crush a material

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6
Q

What is stiffness?

A

The force needed to bend a material

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7
Q

What is hardness?

A

How well a material stands up to wear

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8
Q

What is density?

A

The mass of a given volume of the material, so it is a measure of how heavy the material is.

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9
Q

How can you influence the properties of a given material?

A

Changing the size and shape can have an impact, eg glass can be spun into glass fibres.

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10
Q

How are ropes made?

A

By winding fibres together, the more fibres the stronger the rope.

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11
Q

What does crude oil consist of?

A

It is a mixture of thousands of hydrocarbons, with chains up to 100 carbon atoms long.

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12
Q

What are hydrocarbons mainly used for?

A

Fuel

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13
Q

How does the number of each type of atom change during a chemical reaction.

A

It doesn’t.

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14
Q

Is the composition of crude oil constant?

A

No.

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15
Q

How are the various fractions of crude oil separated?

A

Fractional distillation.

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16
Q

What is the relationship between boiling point, and length of carbon chain, in hydrocarbons?

A

The longer the carbon chain the more energy is required to break out of the liquid, so the boiling point is higher.

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17
Q

How would you make a polymer?

A

You join many smaller molecules called monomers

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18
Q

How many carbons in a polymer?

A

From hundreds to millions.

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19
Q

What is the process for making a polymer?

A

Polymerisation.

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20
Q

Name a monomer and the polymer made from it.

A

Ethene make polyethene.

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21
Q

Molecules are weakly attracted to each other, this force increases as they come closer. If molecules “fit” nicely, would this increase or decrease the melting point?

A

Increase.

22
Q

What is the effect of branching polymer chains on the melting point?

A

The branches hold the molecules apart, reducing the attraction force between the molecules, so the melting point will go down.

23
Q

What is the effect of branched polymer chains on the strength/flexibility of the material?

A

The branches hold the molecules apart, reducing the attraction force between the molecules, so the material will be soft, flexible, weak.

24
Q

What is the effect of long chains in polymers, without any side branches?

A

The molecules are closely aligned, so the attraction force between them is strong. The polymer is therefore strong and hard.

25
Q

What is a crystalline polymer?

A

One that has lots of areas in which there is a regular pattern to the way the molecules line up.

26
Q

What are the properties of crystalline polymers?

A

They are very strong, but can be brittle.

27
Q

What is the effect of lengthening the polymer chain?

A

The material becomes stronger, and the melting point rises as the molecules are larger and more attracted to each other.

28
Q

What is a plasticiser?

A

A small molecule used to keep polymer chains apart, weakening the attractive forces between the molecules.

29
Q

What is the effect of a plasticiser?

A

The material is made more flexible.

30
Q

Name an example of a polymer that can have a plasticiser added.

A

PVC is used for window frames, but can also have a plasticised added to make it suitable for raincoats.

31
Q

What is a thermoplastic?

A

A plastic that can be melted and moulded. Often used to make toys.

32
Q

What is a thermosetting plastic?

A

A plastic that does not melt when heated, due to the cross-links between the molecules.

33
Q

How could you increase the crystallinity of a polymer?

A

Remove branches, make the structure as flat as possible so that the chains can line up.

34
Q

What is the effect of drawing a heated polymer through a tiny hole?

A

The molecular chains will line up, increasing cristallinity and increasing tensile strength.

35
Q

Give an example of a polymer that is produced by drawing through a tiny hole?

A

Kevlar, used for bullet proof vests.

36
Q

What is a nanoparticle?

A

A particle that contains up to a thousand atoms.

37
Q

Name a natural nanoparticles?

A

Salt in seaspray

38
Q

Name a nanoparticle created by accident?

A

Carbon particulates when fuels burn

39
Q

What is nanotechnology?

A

The use and control of very small structures.

40
Q

What is a buckyball?

A

A sphere made from 60 carbon atoms, this is a very strong structure.

41
Q

Why is nanotechnology used with catalysts?

A

The surface area increases as the particles become smaller, and increasing surface area gives more sites for reactions to take place.

42
Q

What is a carbon nanotube?

A

A tube made out of carbon atoms.

43
Q

How long can a nanotube be?

A

The diameter is measure in nanometers, and the length can be millimetres, so they can be millions of times longer than they are wide

44
Q

Why can nanoparticles show different properties to larger particles of the same material?

A

They have a very large surface area.

45
Q

Name some everyday uses of nanoparticles.

A

Silver to kill bacteria, put into plastic food containers, socks, bandages. Titanium oxide is used in sunscreens, the small particles are invisible but still stop sunburn. People therefore don’t have to look ghostly white at the beach.

46
Q

How do you make a composite using nanoparticles?

A

They are mixed with other substances to eg make rubber harder wearing.

47
Q

What are the risks of nanotechnology?

A

New technology, so not totally known. eg silver nanoparticles could be washed out of clothes and coninue killing bacteria, first at the sewage works where they are needed to clean the water, then in the environment. Also used in cosmetics, nanoparticles can cross the skin so effect on human health unknown.

48
Q

Why do some people think there is no risk with nanoparticles?

A

They occur naturally, eg soot and volcanic dust. Hmm.. maybe volcanic lava is also not risky? :D

49
Q

Why do other people think that there are risks with the new technology of nanotechnology?

A

There has not been time to test; there are new nanoparticles so the safety of the natural ones may not be relevant.

50
Q

Why do some people want nanotechnology stopped?

A

They want proof that the new technology will not create health and environmental risks.

51
Q

What is a risk?

A

The chance of an event happening, and the consequences if it did.

Chemistry 21st century (10 decks)

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