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emma- lamda > Structure & Properties > Flashcards

Structure & Properties Flashcards

1
Q

Why do ionic solids have high melting points?

A

They have giant structures with strong electrostatic forces that hold the ions together and a lot of energy is needed to overcome the forces

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2
Q

What can the ions do when an ionic compound has been melted?

A

The ions are free to move

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3
Q

When can ionic compounds conduct electricity?

A

When molten or when dissolves in water and the water molecules split up the lattice

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4
Q

Why can ionic substances conduct electricity when molten or dissolved in a water?

A

They are free to move and carry a charge

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5
Q

Why can’t ionic compounds conduct electricity when solid?

A

The ions can only vibrate about fixed positions they cannot move around

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6
Q

What do the covalent bonds act between?

A

The covalent bonds act only between the atoms within the molecule

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7
Q

Why do simple molecules have relatively low melting points and boiling points?

A

The intermolecular forces between the locales are weak

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8
Q

What sort of boiling and melting points dos impel molecules have?

A

Low MP and BP

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9
Q

Why do cannot simple molecules carry an electrical charge?

A

They have no overall charge so cannot carry a charge

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10
Q

What state of matter do the simplest molecules with the weakest forces such as H2 and Cl2 exist in at room temperature?

A

Gas at room temperature

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11
Q

Which state of matter will larger molecules with stronger attractions exist as at room temperature?

A

Liquids or solids with low melting points

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12
Q

Why are substances with large molecules more likely to be liquids and solids at room temperature?

A

The intermolecular forces are stronger for larger molecules so they will require more energy to overcome so the point when these forces are over some (melting point) will be higher

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13
Q

Why do giant covalent structures/macromolecules have very high melting points?

A

It requires huge amounts of energy to break down the lattice and so these substances have very high melting points

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14
Q

How many atoms of carbon are covalently bonded to each other in diamond?

A

Every carbon atom is covalently bonded to four other carbon atoms

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15
Q

What properties does diamond have?

A

It is very hard and is transparent

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16
Q

Which compound has a similar structure to diamond?

A

Silicon dioxide (silica)

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17
Q

What is diamonds structure like?

A

Regular three dimensional giant structure

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18
Q

How many carbon atoms are covalently bonded in graphite?

A

The atoms are covalently bonded to 3 other carbon atoms

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19
Q

Why can graphite layers slide over each other?

A

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

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20
Q

Give 2 similarities and 2 differences between diamond and graphite

A

Similarities: forms of carbon
Giant covalent structures
Have covalent bonds
Differences: carbon atoms in diamond are bonded to four other carbon atoms only to 3 other atoms in graphite
Diamond is 3D, graphite is 2D
Diamond is hard, graphite is slippery and soft
Diamond is transparent, graphite opaque
Graphite is a good conductor of heat/electricity diamond is a poor conductor
Graphite has delocalised electrons, diamond does not
Graphite has intermolecular forces, diamond does not

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21
Q

In graphite what do the carbon atoms form?

A

A flat sheet of hexagons

22
Q

Why ça granite conduct heat and electricity?

A

It has delocalised electrons wishing are free to more and carry a charge or transfer heat through out the graphite

23
Q

Why can graphite layers slide over each other easily?

A

They have weak intermolecular forces between the layers

24
Q

What are fullerenes?

A

Large molecules formed from hexagonal rings of carbon atoms

25
Q

What are scientists trying to use fullerenes for?

A

Drug delivery into the body, lubricants, catalysts and reinforcing materials

26
Q

Give 2 similarities and one difference between graphite and fullerenes

A

Similarities:
Forms of carbon
Hexagonal rings
Differences:
Graphite is a giant structure, fullerenes are molecules
Graphite is 2d, fullerenes are 3D
Graphite forms large particles, many fullerenes are nano sized

27
Q

What are the BPs like for carbon and graphite?

A

High as they are giant covalent structures with very strong covalent bonds

28
Q

How are metal atoms arranged?

A

In layers

29
Q

Why are metals used for making wires and sheet materials?

A

The layers of atoms can slide over each other. They can move into a new position without breaking apart so the metal can bend or be stretched into a new shape

30
Q

What are alloys?

A

Mixtures of metals or metals mixed with other elements

31
Q

Why are alloys harder than pure metals?

A

The different sized atoms in the mixture distort the layers in the metal structure and make it more difficult for the layers to slide over each other

32
Q

What are shape memory alloys?

A

They can be bent or deformed into a different shape when they are heated they return to their original shape

33
Q

How can shape memory alloys be used?

A

As dental braces or the arms of glasses

34
Q

Give 2 reasons why alloys are more useful than pure metals

A

They are harder than pure metals

They can be made to have specific properties or uses

35
Q

Why are metals good conductors good conductors of electricity?

A

The metals delocalised electrons can move through out the giant metallic lattice and can transfer energy quickly and carry a charge

36
Q

What do the properties of the polymer depend on?

A

The monomers used to make it and the conditions used to carry out the reaction

37
Q

HD polyethylene has a ………. Temperature and is ………. That LD polythene

A

Higher

Stronger

38
Q

Why do LD and HD polythene have different properties?

A

Made using different reaction conditions, they have different structures, differently shaped molecules

39
Q

What are thermos offending polymers?

A

When it is heated it becomes hot and when it cools it becomes hard

40
Q

What are the polymer chains in a thermos offending polymer like?

A

The individual polymer chains are tangled together

41
Q

What are thermosetting polymers?

A

They do not melt or soften when we heat them

42
Q

What are the polymer chains like in thermosetting polymers?

A

There is strong covalent bonds between their polymer chains

43
Q

What holds the ions together in ionic compounds?

A

They have giant structures in which many strong electrostatic forces hold the ions together

44
Q

What are the forces between the polymer chains like in thermosoftening polymers?

A

The forces are weak

45
Q

What happens when we heat thermosoftening polymers?

A

The weak intermolecular forces are broken and the polymer becomes soft when the polymer cools the intermolecular forces bring the polymer molecules back together so the polymer hardens again

46
Q

What are nanoparticles?

A

Particles 1-100nm smaller than normal particles

47
Q

What is nanotechnology being used in?

A

Making catalysts
Cosmetics
Construction materials

48
Q

What could happen if we increasingly use nanoparticles?

A

There will be greater risk of them getting into the air and into our bodies which could have unpredictable consequences for our health and the environment

49
Q

Due to the fact the are incredibly small what else do nanoparticles have?

A

Very large surface area

50
Q

What is special about nanoparticles?

A

They behave differently to ordinary materials and have new properties

emma- lamda (5 decks)

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