C2 - Bonding, Structure and Properties of Matter

Question 1

What are positive and negative ions called?

Answer 1

Positive - Cation
Negative - Anion

Question 2

What is an ionic bond?

Answer 2

When a metal and non-metal react together, the metal atom loses electron to form a cation and the non-metal ion gains electrons to form an anion. These two ions are oppositely charged so they are strongly attracted to each other by electrostatic forces of attraction. This is called an ionic bond.

Question 3

How do you show ionic bonds?

Answer 3

Dot and cross diagram.

Question 4

What structure do ionic compounds have?

Answer 4

Giant Lattice Structure- the ions form a closely packed regular lattice arrangement where there are strong electrostatic forces of attraction between oppositely charged ions in all directions in the lattice.

Question 5

Why do ionic compounds have certain properties?

Answer 5

• High MP/BP: There are many strong, electrostatic forces of attraction between the ions. It takes lots of energy to overcome these forces.
• Conduct electricity: When they’re solid, the ions are held in place, so they can’t move throughout the structure. However, when they are melted or dissolved in water, the ions are free to move throughout the structure or solution, so they’ll carry electrical charge.

Question 6

What is a covalent bond?

Answer 6

When non-metal atoms bond together, they share pairs of electrons. This is called a covalent bond.

Question 7

Why are covalent bonds strong?

Answer 7

The positive nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces of attraction.

Question 8

Evaluate the ways of displaying covalent bonds.

Answer 8

Dot and cross:
+ Show which atoms the electrons come from
- Don’t show the relative sizes of the atoms
- Don’t show how the atoms are arranged in space

Displayed formula:
+ Show how atoms are connected in large molecules
- Don’t show the 3D structure of the molecule
- Don’t show which atoms the electrons in the covalent bond have come from

3D Model:
+ Shows the sizes of the atoms
+ Shows the covalent bonds
+ Shows their arrangement in space next to each other
- Can get confusing when dealing with larger molecules
- Don’t show where the electrons in the covalent bonds have come from

Question 9

What is a simple molecular substance?

Answer 9

They are made up of molecules containing a few atoms bonded together by covalent bonds.

Question 10

What are the properties of simple molecular structures?

Answer 10

• Strong covalent bonds.
• Weak intermolecular forces.
• Low melting and boiling point because only the intermolecular forces need to be overcome, not the bonds.
• Gases and liquids at room temperature.
• Don’t conduct electricity because they aren’t charged, so there are no free electrons or ions.

Question 11

What is a polymer?

Answer 11

A long chain of repeating units.

Question 12

What are all atoms in a polymer joined by?

Answer 12

Strong covalent bonds.

Question 13

How do you find the molecular formula of a polymer?

Answer 13

Write down the molecular formula of the repeating unit inside the brackets and put an n outside.
Example: Polyethene - (C2H2)n

Question 14

Why are polymers solids at room temperature?

Answer 14

Unlike simple covalent molecules, the intermolecular forces between polymer molecules are large, so they require more energy to break them.

Question 15

What are the properties of giant covalent structures?

Answer 15

• Strong covalent bonds.
• High melting and boiling points as lots of energy is needed to break the strong covalent bonds between atoms.
• Don’t conduct electricity as there are no charged particles.

Question 16

What is an allotrope?

Answer 16

Different structural forms of the same element in the same physical state.

Question 17

What are the properties of diamond?

Answer 17

• Each carbon arm has four covalent bonds, so it is very hard.
• It has strong covalent binds which take lots of energy to break, so it has a very high melting point.
• There are no free electrons or ions, so it doesn’t conduct electricity.

Question 18

What are the properties of graphite?

Answer 18

• Each carbon atom is bonded to three other carbon atoms, creating hexagonal layers of carbon atoms.
• There are no covalent bonds between the layers, so they’re held together weakly. This means they’re free to move over each other, making graphite soft and slipper so it’s ideal as a lubricating material.
• Covalent binds require lots of energy to break, so graphite has a high melting point.
• Since one carbon atom is only bonded to three other atoms, there is one delocalised electron that can move throughout the structure. Therefore, graphite conducts electricity and thermal energy.

Question 19

What is graphene and what are it’s properties?

Answer 19

• It is one layer of graphite (carbon atoms joined together in hexagons).
• It is one atom thick, so it is 2D.
• It has lots of strong covalent bonds and is very light, so it can be added to composite materials to make them stronger without adding much weight.
• They also conduct electricity.

Question 20

What is a fullerene?

Answer 20

Molecules of carbon shaped like closed tubes or hollow spheres.

Question 21

What can fullerenes be used for?

Answer 21

• They can deliver a drug into the body as they can trap molecules inside of them.
• They are great industrial catalysts because of their large surface area.
• They are good lubricants.
• They can form nanotubes.

Question 22

Describe metallic bonding.

Answer 22

1) Metals have a giant structure.
2) The delocalised electrons in the outer shell of a metal atom have strong electrostatic forces of attraction with the positive metal ions.
3) These forces hold the atoms together in a regular structure and are known as metallic bonding. Metallic bonding is very strong.

Question 23

What are the properties of metals?

Answer 23

• They have a high melting point and are generally a solid at room temperature because the electrostatic forces between the metals and the delocalised sea of electrons are very strong, so they need lots of energy to be broken.
• They are good conductors of electricity and heat because the delocalised electrons can carry electric charge and thermal energy through the whole structure.
• They are malleable because layers of atoms in a metal can slide over each other.

Question 24

What is an alloy?

Answer 24

A mixture of two or more metals or a metal and another element.

Question 25

Why are alloys harder than pure metals?

Answer 25

Different elements have different sized atoms, so when another element is mixed with a pure metal, the new metal atoms will distort the layers of metal atoms, making it more difficult for them to slide over each other.

Question 26

What does the strength of the forces of attractions between particles depend on?

Answer 26

1) The material such as the structure and type of bonds holding the particles together.
2) Temperature.
3) Pressure.

Question 27

Describe the states of matter.

Answer 27

Solids:
- Strong force of attraction between particles.
- Have a fixed position.
- Have a regular lattice arrangement.
- Do not flow.
- Vibrate about their positions. The hotter the solid becomes, the more they vibrate causing solids to expand slightly when heated.

Liquids:
- Weak force or attraction between particles.
- Randomly arranged.
- Particles are free to move past each other, but they tend to stick closely together.
- Have a definite volume, but don’t have a definite shape.
- Flow to fill the shape of the container.
- Move in a random motion. The hotter the liquid, the faster they move, so liquids expand slightly when heated.

Gases:
- Very weak forces of attraction between particles.
- Particles are free to move and at far apart.
- Particles travel in straight lines.
- Don’t have a fixed shape or volume.
- Fill the container.
- Move in a random motion. The hotter the gas gets, the faster they move. Gases either expand when heated, or their pressure increases.

Question 28

What does aqueous mean?

Answer 28

Dissolved in water.

Question 29

What are all the changes in state called?

Answer 29

• Melting: Solid to liquid.
• Boiling/evaporating: Liquid to gas.
• Condensing: Gas to liquid.
• Freezing: Liquid to gas.
• Sublimation: Solid to gas.
• Deposition: Gas to solid.

Question 30

Order the types of particles by size.

Answer 30

1) Coarse particles (between 2.5 X 10^-6m and 1 X 10^-5m).
2) Fine particles (between 1 X 10^-7m and 2.5 X 10^-6m).
3) Nanoparticles (between 1 X 10^-9m and 1 X 10^-7m).

Question 31

How much is one nanometre in metres?

Answer 31

1 X 10^-9 metres.

Question 32

Why would you need less of a material if it’s made up of nanoparticles?

Answer 32

It has a high surface area to volume ratio, so you’ll need less of the material for it to work as an effective catalyst instead of using regular particles in bulk.

Question 33

What are the uses of nanoparticles?

Answer 33

1) They have a high surface area to volume ratio, so they can help make new catalysts.
2) Nanomedicine. They are absorbed more easily by the body than most particles, so they can deliver drugs right into the cells where they’re needed.
3) Some nanoparticles conduct electricity, so they can be used in electrical circuits for computer chips.
4) Silver nanoparticles have antibacterial properties, so they can be added to polymer fibres to make surgical masks and wound dressing as well added to deodorants.
5) Cosmetics. For example, they’re used to improve moisturises without making them oily.

Question 34

What is a negative of nanoparticles?

Answer 34

The effects on the human body aren’t fully understood as we don’t know the long term effects of them.

Question 35

Evaluate the use of nanoparticles in a product.

Answer 35

• They are used in sun creams.
+ Better at protecting skin from harmful UV rays.
+ Give better skin coverage.
- Unclear if they can get into your body or if they damage cells.
- Don’t know if they damage the environment when they are washed away.