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

1
Q

Do simple molecules conduct electricity?

A

No

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2
Q

Why do simple molecules not conduct electricity?

A

because the molecules do not have an overall change

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3
Q

Why do ionic compounds have high melting and boiling points?

A

as there are strong electrostatic forces in all directions between oppositely charged ions. Large amounts of energy are needed to break many strong bonds

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4
Q

When can ionic compounds conduct electricity, why?

A

when melted or dissolved in water.

can conduct electricity because ions can move and carry a current

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5
Q

give an example of an ionic compound

A

sodium chloride

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6
Q

Why do giant covalent structures- macromolecules, have high boiling and melting points?

A

As all atoms are linked to other atoms by strong covalent bonds.

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7
Q

How many covalent bonds does carbon form in diamond?

A

4

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8
Q

How many covalent bonds does carbon form in graphite?

A

3

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9
Q

Why are there layers in graphite?

A

As each carbon atom bonds to 3 other carbon atoms

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10
Q

Why is graphite soft and slippery?

A

each carbon bonds with 3 other carbon atoms which forms layers. Layers are free to slide over each other as there are no covalent bonds between the layers so therefore weak intermolecular forces between layers.

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11
Q

Why can graphite conduct electricity?

A

One electron from each carbon atom in graphite is delocalised. These delocalised electrons allow graphite to conduct heat and electricity

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12
Q

Describe the structure of fullerenes

A

hexagonal rings of carbon atoms

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13
Q

What can fullerenes be used for?

A

drug delivery into the body. in lubricants, as catalysts, and in nanotubes for reinforcing materials eg in tennis rackets

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14
Q

What does conduction depend on?

A

the ability of electrons to move throughout the metal

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15
Q

Why do metals conduct heat and electricity?

A

because of the delocalised electrons in their structures

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16
Q

Why can metals be bent and shaped?

A

atoms arranged in regular layers. These layers are able to slide over each other.

17
Q

Why are alloys harder than pure metals?

A

Alloys are made from 2 or more different metals. The different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other.

18
Q

Give an example of a shape memory alloy

A

Nitinol used in dental braces

19
Q

What do shape memory alloys do?

A

return to their original shape after being deformed

20
Q

What do the properties of polymers depend on?

A

what they are made from and the conditions under which they are made

21
Q

What conditions are needed to make low density polythene?

A

high temperature and pressure

22
Q

What conditions are needed to make high density polythene?

A

Lower temperature and pressure

catalyst

23
Q

Describe the structure and properties of thermosoftening polymers

A

individual, tangles polymer chains. Weak intermolecular forces between chains so easy to separate, melt and recycle

24
Q

Describe the structure and properties of thermosetting polymers

A

polymer chains with cross links (covalent bonds) between them so strong intermolecular forces between bonds. Means that they do not melt when heated- high melting point so can not be recycled

25
Q

What structures does nanoscience refer to?

A

structure that are 1-100 nanometers in size and contain a few hundred atoms.

26
Q

4 key points about nanoparticles

A
  • 1-100 nanometers in size
  • contain a few hundred atoms
  • nanoparticles show different properties to the same materials in bulk
  • have a high surface area to volume ratio
27
Q

What can nanoparticles be used to make?

A

new computers, catalysts, stronger and lighter construction materials, new cosmetics

28
Q

Why do substances that consist of simple molecules have relatively low melting and boiling points?

A

There are weak intermolecular forces between the molecules. It is these intermolecular forces that are easily overcome, not the strong covalent bonds when a substance melts or boils.

29
Q

Why is silica used to make brinks for high temperature furnaces?

A

It has a high melting point (it is a macromolecule)

because each silicon atom is covalently bonded to 4 oxygen atoms

These covalent bonds are very strong so a lot of energy is needed to break them

it is unreactive , hard and a poor conductor of heat as there are no free electrons

30
Q

Explain why nanoparticles pass through the skin and travel around the body more easily than normal-sized particles

A

as they are smaller- only a few atoms in size

so they can easily pass through the skin

31
Q

Explain why thermosoftening polymers would not be suitable for packaging very hot food

A

They have a low melting point so would melt

This is because there are no crosslinks between chains

so there are weak intermolecular forces

32
Q

Why is silicon dioxide a suitable material for lining furnaces?

A

It has a high melting point (as it is a macromolecule)

because a lot of energy is needed to break bonds

This is because the bonds are covalent and so are very strong

33
Q

Explain why copper is a good conductor of electricity

A

Copper has delocalised electrons which can move through the structure and carry a charge

34
Q

Explain why carbon dioxide has a very low boiling point

A

Carbon dioxide is simple molecular

There are weak intermolecular forces between the molecules

so only a small amount of energy is needed to separate the molecules

35
Q

Explain why graphite is softer than diamond

A

because there are layers in graphite that can slide

this is because there are only weak intermolecular forces between layers

however in diamond, each carbon atom is covalently bonded to 4 others

so no carbon atoms are able to move

36
Q

Explain hy graphite conducts electricity but diamond does not

A

because graphite has delocalised electrons which can carry a current and move throughout the structure

however, diamond has not delocalised electrons

37
Q

Suggest why carbon nanotubes are used as lubricants

A

nanotubes can slide over each other

because no covalent bonds between the nanotubes