C3: Structure and Bonding

Question 1

What are the properties of solids?

Answer 1

They are hard to compress
- packed in a regular pattern with almost no space between particles
Fixed shape - cannot flow
Vibrate in place

Question 2

What are the properties of liquids?

Answer 2

Hard to compress
-particles are close together with little space
Take the shape of the container, can flow
Slide along each other
Particles vibrate faster

Question 3

What are properties of gas particles?

Answer 3

Easy to compress
- particles are far apart
Spread out to fill the space of the container
Move quickly and randomly

Question 4

Why is it harder to change the state of some materials?

Answer 4

Some have stronger intermolecular forces of attraction, thus more energy is required to break them, thus the higher the melting point

Question 5

What are the limitations of the simple particle model?

Answer 5

The model assumes all particles are solid spheres (particles have different shapes and are not solids)
Forces between particles are not shown (incorrect)

Question 5

What is ionic bonding?

Answer 5

The bonding taking place between a metal and a non-metal. It takes place for both to achieve a full outer shell

Question 6

What is a dot and cross diagram?

Answer 6

A diagram representing ionic bonding - only needs to show outer energy levels. Usually, metals are modelled with crosses as their electrons and non-metals are modelled with dots to distinguish the electrons.
To model ions add square brackets around the ions and the sign on the outside

Question 7

What are the properties of ionic compounds?

Answer 7

They form giant ionic lattices (every + ion is surrounded by a - ion)
Cannot conduct electricity when solid, but can when liquid

Question 8

What are the properties of giant ionic lattices?

Answer 8

Very strong electrostatic forces (ionic bonds) of attraction - high m.p. and b.p., lots of heat to break

Question 9

Why can’t ionic structures conduct electricity when solid?

Answer 9

Their ions are locked in place by the electrostatic forces of attraction. They conduct when liquid because then, the ions can move and carry a charge

Question 10

What is covalent bonding?

Answer 10

Takes place between two non-metals. They share pairs of electrons to form full outer shells

Question 11

How is covalent bonding modelled as energy level diagram?

Answer 11

The atoms are modelled as circles with their electrons modelled as dots and crosses respectively (only outer shells required). Their bond is shown as an overlap, with their shared electrons inside the overlapping space

Question 12

Why do small covalent molecules have low m.p. and b.p.?

Answer 12

Although the atoms are held together by strong covalent bonds, the intermolecular forces between the molecules are very weak, thus require low energy to break

Question 13

What happens to m.p .and b.p. of covalent structures as their size increases?

Answer 13

They increase, this is because there are now more intermolecular forces, which need more energy to break.

Question 14

Why don’t small covalent molecules conduct electricity?

Answer 14

Covalently bonded molecules have no charge, thus cannot carry a current

Question 15

What is the structure of giant covalent molecules?

Answer 15

Many covalently bonded molecules joined together in a giant covalent lattice

Question 16

What are the properties of giant covalent molecules?

Answer 16

Always solids at room temp.

Question 17

Why are giant covalent molecules solids at room temp.?

Answer 17

They have millions of strong covalent bonds, taking more energy to break them

Question 18

What is the structure of diamond?

Answer 18

Each carbon atom forms 4 covalent bonds with other carbon atoms - a single diamond contains a huge amount of these covalent bonds, resulting in a very high melting point

Question 19

Why can’t diamond conduct electricity?

Answer 19

It contains no free electrons to carry electrical charge

Question 20

What is the structure of silicon dioxide (silica or sand)?

Answer 20

Oxygen atom covalently bonded to a silicon atom - it has a huge number of these

Question 21

What are the properties of silicon dioxide?

Answer 21

High melting and boiling points

Question 22

What are the properties of graphite?

Answer 22

High m.p. and b.p.
Soft and slippery
Excellent conductor of electricity and heat

Question 23

What is the structure of graphite?

Answer 23

Carbon atoms with 3 covalent bonds each. They form many hexagonal rings (as there’s a lot of them, graphite has a high m.p. and b.p.). These are arranged in layers which are not covalently bonded, thus they can slide, making graphite slippery. Instead, they are held together by the single electron of each carbon atom which is not in a covalent bond

Question 24

Why is graphite a good conductor of heat and electricity?

Answer 24

Delocalised electrons can move, meaning they can conduct heat and electricity

Question 25

What is graphene?

Answer 25

A single layer of graphite, one atom thick

Question 26

What are the properties of graphene?

Answer 26

Excellent conductor of electricity (has delocalised electrons)
Extremely strong

Question 27

Where is graphene used?

Answer 27

Electronics, medicine, transport

Question 28

What are fullerenes?

Answer 28

Molecules of carbon atoms with hollow shapes, they usually have hexagonal rings of carbon atoms

Question 29

What’s the name of the fullerene that was in the first question of last year’s mock paper and what is its shape?

Answer 29

Buckminsterfullerene - sphere

Question 30

What are the uses of fullerenes?

Answer 30

Pharmaceutical delivery
Lubricants
Catalysts

Question 31

What are the uses of carbon nanotubes?

Answer 31

High tensile strength - stretched w/o breaking
Excellent conductors of heat and electricity

Question 32

What is the structure of metals?

Answer 32

A giant structure arranged in layers, electron on their outer shells are delocalised

Question 33

What is metallic bonding?

Answer 33

The bonding between two metals, they have a ‘sea of delocalised electrons’. As they have now lost their outer electron, a positive metal ion is formed. Thus, there is now a strong electrostatic attraction (metallic bond) between the delocalised electrons and the positive metal ions

Question 34

What are the properties of metals?

Answer 34

High m.p./ b.p.
Conduct heat and electricity
Can be bent and shaped

Question 35

Why do metals have high m.p. and b.p.?

Answer 35

They have strong metallic bonds, taking a lot of energy to break

Question 36

Why are metals good conductors?

Answer 36

They have delocalised electrons which can carry charge and move around (passing the energy more quickly)

Question 37

Why can metals be bent and shaped?

Answer 37

The layers of atoms in metals are able to slide over each other

Question 38

How can metals be hardened?

Answer 38

Make an alloy

Question 39

What is an alloy?

Answer 39

A mixture of metals
- different sizes of atoms distorts the layered structure of the metals, making it more difficult for them to slide over each other - making them harder than pure metals

Question 40

What is the value of a nanometre?

Answer 40

1 nm = 1/1,000,000,000 m
1nm = 1/1,000,000 mm
1nm = 1/1000 mum

Question 41

What is the size of nanoparticles?

Answer 41

1 - 100 nm diameter
- contain only a few hundred atoms

Question 42

What happens when you decrease the particle size?

Answer 42

The SA:V ratio increases by the same amount

Question 43

What is the SA:V ratio of nanoparticles?

Answer 43

Huge, a much smaller quantity of nanoparticles is needed compared to a normal sized particles

Question 44

What are the uses of nanoparticles?

Answer 44

Sunscreens
Cosmetics
Deodorants
Electronics
Catalysts
Medicines

Question 45

What are the risks of nanoparticles?

Answer 45

They can be absorbed into the body and enter cells
- causing breathing problems
- washing clothing with silver nanoparticles can harm aquatic life