Structures and bonding

Question 1

Name the properties of simple covalent molecules

Answer 1

• Low melting and boiling points
• Usually gases at room temperature
  (except water)
• Don’t conduct electricity

Question 2

Explain the properties of simple covalent bonds

Answer 2

• Low melting and boiling points as they are held together by weak intermolecular forces which require little energy to break
• Don’t conduct electricity as their molecules have no overall charge

Question 3

Why can’t simple covalent molecules conduct electricity?

Answer 3

• Don’t conduct electricity as their molecules have no overall charge

Question 4

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

Answer 4

• They’re held together by weak intermolecular forces which require little energy to break

Question 5

Name the properties of giant covalent structures

Answer 5

• Solid at room temperature

- High melting and boiling points

Question 6

Name 4 giant covalent structures

Answer 6

Diamond, Silicon Dioxide, Graphite and Graphene

Question 7

Describe and explain the properties of Diamond

Answer 7

• Formed from carbon bonded to itself 4x
• High melting and boiling points as they have a large
  number of strong covalent bonds that are hard to break
• Can’t conduct electricity as there are no free electrons
  to carry charge

Question 8

Why do giant covalent structures have high melting and boiling points while simple covalent molecules don’t?

Answer 8

As the size of the molecule increases, the intermolecular forces get stronger.

Question 9

Describe and explain the properties of Silicon Dioxide

Answer 9

• Silicon bonded to oxygen
• High melting and boiling point due to large number
  of strong covalent bonds

Question 10

Describe and explain the properties of graphite

Answer 10

• Carbon bonded to itself 3 times
• High melting and boiling point due to a large number
  of strong covalent bonds
• Soft and slippery as there are no covalent bonds
  between its layers/lattices
• Good conductors of heat and electricity as they have
  delocalised electrons.

Question 11

Explain why graphite can conduct electricity and heat

Answer 11

In every graphite molecule, there is one electron not covalently bonded, these are released from the atom, and are called delocalised electrons. These electrons can move, so graphite can conduct heat and electricity

Question 12

How many times is carbon bonded to itself in graphite and diamond?

Answer 12

Graphite - 3x

Diamond - 4x

Question 13

What is graphene?

Answer 13

A single layer of graphite

Question 14

What is a use of graphite?

Answer 14

A lubricant

Question 15

Describe the structure of graphite

Answer 15

Layers of carbon atoms in hexagonal rings

Question 16

Describe and explain the properties of graphene

Answer 16

• One atom thick (a single layer of graphite)
• Good conductor as it contains delocalised electrons
• Very strong

Question 17

What are fullerenes?

Answer 17

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

Question 18

What are some uses of fullerenes?

Answer 18

• Pharmaceutical deliveries (into the body)
• Lubricants
• Catalysts

Question 19

What are carbon nanotubes?

Answer 19

Fullerenes shaped into long cylinders with a high length to diameter ratio

• Used in electronics, nanotechnology and materials

Question 20

Describe the properties of carbon nanotubes

Answer 20

• High tensile strength (can be stretched without
  breaking)
• Good conductors of heat and electricity

Question 21

Give one use of carbon nanotubes

Answer 21

To reinforce materials e.g. Tennis rackets

Question 22

What are nanoparticles?

Answer 22

Particles with a diameter between 1-100nm that only contain a few hundred atoms

Question 23

What is the relative size of a coarse particle (PM10)

Answer 23

Diameter between 1x10⁻⁵m and 2.5x10⁻⁶m

-They contain many thousands of atoms

Question 24

What is the relative size of a fine particle?

Answer 24

Diameter between 100 and 2500nm

1x10⁻⁷m and 2.5x10⁻⁶m
Contain several thousand atoms

Question 25

Describe the relationship between particle size and surface area : volume ratio

Answer 25

As the particle size decreases by 10x, the surface are to volume ratio increases by 10x

Question 26

Why are nanoparticles useful in chemical reactions?

Answer 26

They have a high surface area : volume ratio meaning that a smaller quantity is required than if a larger particle were to be used

Question 27

What are some uses of nanoparticles?

Answer 27

• Medicines
• Sun creams
• Cosmetics
• Deodorants
• Electronics
• Catalysts

Question 28

What is a risk of using nanoparticles in products like sun creams?

Answer 28

It is possible that nanoparticles can be absorbed into the body and enter body cells. The potential long term effects of this are unknown.

Question 29

Describe the structure and bonding in Sodium Chloride (4)

Answer 29

• It’s a giant ionic structure/lattice
• Containing ions
• Na+ and Cl-
• Held together by the electrostatic force

Question 30

Why might sock manufacturers use silver nanoparticles in their socks?

Answer 30

To remove odour/kill bacteria or microorganisms

Question 31

Why might some people be worried wearing clothes made with nanoparticles?

Answer 31

nanoparticles / ions might penetrate skin and get into bloodstream, where they could accumulate in organs, possibly causing health issues.

Question 32

What are the 5 uses of nanoparticles?

Answer 32

• Sunscreens
• Cosmetics
• Deodorants
• Electronics
• Catalysts

Question 33

Why are nanoparticles more effective than normal sized particles?

Answer 33

They have a high surface area:volume ratio, and therefore less is required to produce the same/a similar effect.

Question 34

Describe the structure of a metal and why it can conduct electricity when solid (3)

Answer 34

• They contain many positive ions surrounded by a sea of
  electrons, which can move throughout the structure and
  carry charge

Question 35

Why are ball and stick diagrams not true representations of ionic compounds?

Answer 35

The ions should be touching and shouldn’t have gaps between them

Question 36

Why is it called the periodic table?

Answer 36

Similar properties occur at regular intervals