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Chemistry: C2 > C2.2 How structure influences the properties and uses of substances > Flashcards

C2.2 How structure influences the properties and uses of substances Flashcards

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1
Q

What are substances that consist of simple molecules?

A

Gases, liquids or solids that have relatively low melting and boiling points

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2
Q

What forces do substances that consist of simple molecules have between the molecules?

A

Weak intermolecular forces

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3
Q

Which forces are overcome in a simple molecular substance?

A

The intermolecular forces, not the covalent bonds

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4
Q

Why do substances that consist of simple molecules not conduct electricity?

A

They do not have an overall electric charge

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5
Q

What are some examples of substances that consist of simple molecules?

A

Chlorine, oxygen and water

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6
Q

What structures do Ionic compounds have?

A

Regular structures, Giant Ionic Lattices

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7
Q

What do Giant ionic lattices have?

A

Strong electrostatic forces in all directions between oppositely charged ions

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8
Q

Why do ionic compounds have high melting and boiling points?

A

Because large amounts of energy are needed to break the many strong bonds

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9
Q

When do ionic compounds conduct electricity and why?

A

When melted or dissolved in water because the ions are free to move and carry the current

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10
Q

What can atoms that share electrons also form aside form simple molecular substances?

A

Giant covalent structures / macromolecules

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11
Q

What are some example of giant covalent structures (lattices)?

A

Diamond, silicon dioxide and graphite

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12
Q

How are atoms linked in giant covalent structures?

A

By strong covalent bonds

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13
Q

What do the strong covalent bonds in giant covalent structures result in them having?

A

Very high melting and boiling points

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14
Q

In diamond, how many covalent bonds does each carbon atom form?

A

Four, so diamond is very hard

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15
Q

In graphite, how many covalent bonds does each carbon atom form?

A

Three, forming layers

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16
Q

Why is graphite soft and slippery?

A

There are no covalent bonds between the layers so they are free to slide over each other

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17
Q

Why can the layers of graphite be rubbed off so easily?

A

There are weak intermolecular forces between the layers

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18
Q

Why is graphite a good conductor of heat and electricity?

A

Because each carbon atom has a delocalised electron which can move freely through the structure carrying the current, allowing graphite to conduct heat and electricity

19
Q

What else can carbon atoms form?

A

Fullerenes with different numbers of carbon atoms

20
Q

What is the structure of fullerenes?

A

Hexagonal rings of carbon atoms

21
Q

What can fullerenes be used for?

A

Drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials e.g. in tennis rackets

22
Q

Why do metals conduct heat and electricity?

A

Because of their delocalised electrons which are free to move around the whole structure

23
Q

Why can metals be bent and shaped?

A

The layers in metals are free to slide over each other

24
Q

What are alloys?

A

They are made up of two or more different metals

25
Q

Why are alloys harder than pure metals?

A

The different sized atoms of the metals distort the layers in the structure making it more difficult for them to slide over each other

26
Q

What can shape memory alloys do?

A

Return to their original shape after being deformed

27
Q

What is an example of a shape memory alloy?

A

Nitinol used in dental braces

28
Q

How does nitinol work in dental braces?

A

Nitinol can change shape when cooled but when heated it returns back to its original shape. When used for dental braces it warms in the mouth then tries to return to its remembered shape and pulls the teeth with it

29
Q

What do the properties of polymers depend on?

A

What they are made from and under what conditions

30
Q

How are low density and high density poly(ethene) produced?

A

Using different catalysts and different reaction conditions

31
Q

What are the properties of low density poly(ethene)?

A

It is flexible

32
Q

How is low density poly(ethene) made?

A

By heating ethene to about 200 degrees under high pressure

33
Q

What are the properties of high density poly(ethene)?

A

It is rigid

34
Q

How is high density poly(ethene) made?

A

At lower temperatures and lower pressure with a catalyst

35
Q

What do thermosoftening polymers consist of?

A

Individual, tangles polymer chains

36
Q

What do thermosetting polymers consist of?

A

Polymer chains with cross links between them so that they do not melt when they are heated

37
Q

What holds thermosoftening polymers together?

A

Weak intermolecular forces so they are free to slide over each other. This makes them easy to melt and remould these plastics

38
Q

What holds thermosetting polymers together?

A

Strong intermolecular forces between the chains making them strong, hard and rigid

39
Q

What size are nanoparticles?

A

1-100 nanometres

40
Q

How many atoms do nanoparticles roughly contain?

A

100 atoms

41
Q

Why could nanoparticles help as catalysts?

A

They have a huge surface area compared to volume

42
Q

What can nanoparticles be used to make?

A

New stronger and lighter construction materials, new cosmetics such as sun tan lotions and deodorants, new catalysts, new medicine, new lubricant coatings, new computers, highly selective sensors

43
Q

What can fullerenes be joined together to form?

A

Nanotubes

Chemistry: C2 (7 decks)

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