C2.2 Structure, Properties and Uses of Substances

Question 1

Ionic compounds have a regular arrangement of ions called…

Answer 1

A giant ionic lattice

Question 2

Why do ionic compounds have high melting and boiling points?

Answer 2

Because they have strong electrostatic attractions between ions - which require a large amount of energy to be overcome

Question 3

What happens when ionic compounds melt?

Answer 3

There are ions are free to move, and will carry electric charge

Question 4

What happens when ionic compounds dissolve in water?

Answer 4

Ionic compounds dissolve easily in water, the ions separate and are free to move so they carry electric charge

Question 5

What are simple molecules?

Answer 5

Substances with covalent bonds, and molecules made up of only a few atoms e.g. Hydrogen and Oxygen (which travel in pairs)

Question 6

What are the properties of simple molecules?

Answer 6

They have low melting and boiling points, they are mostly gas or liquid at room temp, and they don’t conduct electricity

Question 7

Why do simple molecules have low melting and boiling points?

Answer 7

The intermolecular forces between the molecules are extremely weak and can be easily overcome.

Question 8

What are the differences between giant covalent structures and giant ionic structures (lattices)?

Answer 8

They are similar, but giant covalent structures have no charged ions, all atoms are bonded to each other by strong covalent bonds and they do not conduct electricity

Question 9

Do giant covalent structures have high or low melting/boiling points?

Answer 9

High, because they have strong covalent bonds between energy which require a lot of energy to be overcome

Question 10

What are examples of giant covalent structures?

Answer 10

Diamond, graphite and silicon dioxide

Question 11

What is the structure of a diamond?

Answer 11

Each carbon atom forms 4 covalent bonds in a very rigid giant covalent structure - diamond is the hardest natural substance and is used for drill tips

Question 12

How is graphite structured?

Answer 12

Each carbon atom only form 3 out of a possible 4 covalent bonds, this creates layers of carbon atoms

Question 13

What does the layers in graphite mean it can do?

Answer 13

The layers are free to slide over each other because there are no covalent bonds between them - the layers can be rubbed off on paper (pencil). Graphite is soft and slippery

Question 14

How are the layers in graphite held together?

Answer 14

Weak intermolecular forces hold the layers together, but these forces are easily overcome

Question 15

Is graphite a good conductor?

Answer 15

Because the carbon atoms have only formed 3 out of 4 possible covalent bonds, there are delocalised electrons which can move freely throughout the layers - making graphite a good conductor of heat and electricity

Question 16

How are metals structured?

Answer 16

Metal atoms are held together in a regular structure

Question 17

Why can metals be bent and shaped?

Answer 17

The atoms form layers that are able to slide over each

Question 18

Why are metals good conductors of heat and electricity?

Answer 18

Because they have delocalised electrons that are free to move through the whole structure - these electrons carry the current and heat energy through the structure

Question 19

What are alloys?

Answer 19

Two or more metals mixed together

Question 20

Why are alloy harder than pure metals?

Answer 20

Because they contain different sized atoms (as elements have different sized atoms) which makes it harder for the atoms to slide over each other

Question 21

What are nanoparticles?

Answer 21

Tiny particles 1-100 nanometres across

Question 22

What properties do something silver nanoparticles have compared to the bulk chemical?

Answer 22

Silver nanoparticles kill bacteria and are used in surgical masks, normal silver particles are much bigger and can’t kill particles

Question 23

What new uses of nanoparticles are being developed?

Answer 23

Nanoparticles have a huge surface area so they could be used as catalysts, nanotubes can be used to make stronger, lighter building materials, new cosmetics like sun tan cream and deodorant - they do their job and don’t leave white marks on the skin, lubricant and nanotubes could be used in electrical circuits for computer chips

Question 24

What are fullerenes?

Answer 24

A type of nanoparticle

Question 25

How are fullerenes structured?

Answer 25

Molecules of carbon arranged in hexagonal rings, are shaped like hollow balls or closed tubes

Question 26

What are uses of fullerenes?

Answer 26

Lubricants, catalysts, medicine - they’re easily absorbed by the skin so could help deliver drugs to a specific location and fullerenes can be joined to make nanotubes

Question 27

Properties of nanotubes?

Answer 27

The covalent bonds make carbon nanotubes very strong, they can be used to reinforce materials like graphite in tennis rackets

Question 28

What is a polymer?

Answer 28

Very large molecules formed of many small molecules (monomers)

Question 29

How are polymers bonded?

Answer 29

Strong covalent bonds hold the atoms together in long chains

Question 30

Name two different types of polymers

Answer 30

Thermosoftening and thermosetting polymers

Question 31

What are thermosoftening polymers made of?

Answer 31

Individual tangled chains of polymers like spaghetti

Question 32

How are thermosetting polymers structured?

Answer 32

They have cross-links between polymer chains

Question 33

What are the properties of thermosetting polymers?

Answer 33

Due to the cross-links, they don’t melt when heated, when it reaches a certain temperature it just burns

Question 34

What determines the properties of a polymer?

Answer 34

The intermolecular forces between the polymer chains

Question 35

Why are thermosetting polymers strong, hard and rigid?

Answer 35

The cross-links between the polymer chains are very strong - holding the chains firmly together in a solid structure

Question 36

How are the chains held together in thermosoftening polymers?

Answer 36

They have weak intermolecular forces between chains, and are free to slide over each other. These forces are very weak and are easy to overcome so the plastic is easy to melt.

Question 37

What happens when thermosoftening polymers cool after melting?

Answer 37

The polymer hardens into a new shape, you can melt these polymers and remould them as many times as you like making it easy to recycle

Question 38

How are different types of polythene made?

Answer 38

By using different conditions when being made

Question 39

How is low density polythene made?

Answer 39

By heating ethane to about 200°C under high pressure

Question 40

What are the properties of low density polythene?

Answer 40

It is flexible and used for bags and bottles

Question 41

How is high density polythene made?

Answer 41

Made at low temperatures, low pressure and is with a catalyst

Question 42

Properties of high density polythene

Answer 42

Rigid and used for water tanks and drainpipes

Question 43

What are smart materials?

Answer 43

Substances that behave differently depending on the condition

Question 44

What are shape memory alloys?

Answer 44

A type of smart material - it’s shape can be changed, but they will return to their original shape when heated