Bonding, structure and the properties of matter 2

Question 1

Allotropes

Answer 1

Substances made from the same element in the same physical state but with different structures.

Question 2

Name the allotropes of carbon

Answer 2

-Diamond
-Graphite
-Graphene
-Fullerenes and nanotubes

Question 3

Graphene

Answer 3

-A single layer of graphite

-2D, hexagonal lattice

-Each carbon atom makes 3 bonds so delocalised electrons which can flow and carry charge.

-Properties which make it good in electronics and composites

Question 4

Diamond

Answer 4

-In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure.

-This regular 3D lattice formed is very strong, hard, has very high melting and boiling points, and does not conduct electricity.

Question 5

Graphite

Answer 5

-In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings

-There are no covalent bonds between the layers.

-One electron from each carbon atom is delocalised. (so graphite can conduct electricity and thermal energy)

Question 6

Graphene

Answer 6

Graphene is a single layer of graphite, which consists of carbon atoms arranged into flat hexagons.

Each carbon has one delocalised electron, so graphene can conduct electricity.

Question 7

Fullerenes

Answer 7

-Molecules of carbon atoms with hollow shapes.

-The structure of fullerenes is based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms.

Question 8

How can we use fullerenes in industry?

Answer 8

They can be used to ‘cage’ other molecules so can be used in the delivery of medicines around the body.

They have a high surface area to volume ration so make good industrial catalysts. (individual catalyst molecules could be attached to the fullerene)

Lubricants

Question 9

metallic bonding

Answer 9

In metallic bonding, electrons are delocalised from the lattice of metal ions.

These electrons can carry charge, and so metal acts as a conductor of electricity.

These electrons can also carry thermal energy, meaning metals are good conductors of heat.

Question 10

Alloy

Answer 10

A mixture of metals

Question 11

Do alloys or pure metals have a higher strength?

Answer 11

Alloys because the atoms/ions of the different elements are different sizes, which disrupts the regular layered structure and so means the layers can no longer slide over one another.

Question 12

Why are nanoparticles good catalysts in chemical reactions?

Answer 12

They have a very high surface area to volume ratio, meaning less material is needed compared to another substance.

Question 13

Silver nanoparticle uses

Answer 13

They have antibacterial properties so can be added to the polymer fibres used to make surgical masks and wound dressings to reduce the risk of infection.

They can also be added to deodorants,

Question 14

What properties of graphene make it good in electronics?

Answer 14

-Transparent
-Strong
-Can conduct electricity

Question 15

What properties of graphene make it good in composites?

Answer 15

-The network of covalent bonds make it very strong

-Yet it’s light

-So, it can be added to composite materials to improve their strength without adding much weight

Question 16

Why doesn’t diamond conduct electricity?

Answer 16

It has no free electrons or ions.

Question 17

Why does graphite have a high melting point?

Answer 17

The covalent bonds in the layers need a lot of energy to break.

Question 18

Why is graphite ideal as a lubricating material?

Answer 18

-There are no covalent bonds between the layers - they are only held together by weak intermolecular forces

-So, layers can slide over each other

-This makes graphite soft and slippery

Question 19

How is graphite similar to metals?

Answer 19

It has delocalised electrons.

Question 20

What was the first fullerene to be discovered?

Answer 20

-Buckminsterfullerene (C₆₀)

-Which has a spherical shape.

Question 21

What do we mean by saying fullerenes can ‘cage’ other molecules?

Answer 21

The fullerene structure forms around another atom or molecule, which is then trapped inside.

Question 22

What are carbon nanotubes?

Answer 22

-Cylindrical fullerenes with very high length to
diameter ratios.

-Their properties make them useful for
nanotechnology, electronics and materials

Question 23

Properties of carbon nanotubes

Answer 23

-can conduct electricity and thermal energy

-high tensile strength (don’t break when stretched)

Question 24

Nanotechnology

Answer 24

Technology that uses very small particles such as nanotubes.

Question 25

Nanotubes can be used to strengthen materials without…

Answer 25

..adding much weight.

e.g. in tennis racket frames.

Question 26

What does nanoscience refer to?

Answer 26

Structures that are 1–100 nm in size, containing only a few hundred atoms (nanoparticles)

Question 27

Which particles are nanoparticles smaller than?

Answer 27

Fine particles

Question 28

Which particles are fine particles smaller than?

Answer 28

Coarse particles

Question 29

What are fine particles? (PM₂.₅)

Answer 29

Particles which have diameters between 100 and 2500 nm.

(1 x 10-7 m and 2.5 x 10-6 m).

Question 30

What are coarse particles? (PM₁₀)

Answer 30

Particles which have diameters between 1 x 10-5 m and 2.5 x 10-6 m.

-Often referred to as dust.

Question 31

What happens to the surface area to volume ratio if the side of cube decreases by a factor of 10?

Answer 31

It increases by a factor of 10.

Question 32

Why may nanoparticles have properties different from those for the same materials in bulk?

Answer 32

-Because of their high surface area to
volume ratio.

-This may also mean that smaller quantities are needed to be effective than for materials with normal particle sizes.

Question 33

How many metres are in 1 nm?

Answer 33

0.000 000 001 m

Question 34

What is the diameter of a typical atom?

Answer 34

1 x 10⁻¹⁰ m

Question 35

Where do nanoparticles have applications?

Answer 35

-In medicine

-In electronics

-In cosmetics and sun creams

-As deodorants

-As catalysts

Question 36

How are nanoparticles used in cosmetics?

Answer 36

e.g. to improve moisturisers without making them really oily

Question 37

Some nanoparticles conduct electricity, so…

Answer 37

…can be used in tiny electrical circuits for computer chips.

Question 38

How could nanoparticles be used in medicine? (nanomedicine)

Answer 38

-Nanoparticles are absorbed more easily by the body than most particles because they are smaller

-This means they could deliver drugs right into cells where they’re needed

Question 39

New applications for nanoparticulate materials are…

Answer 39

…an important area of research.

Question 40

The effect of nanoparticles on the body isn’t…

Answer 40

…fully understood.

So, it’s important that any new products are tested thoroughly to minimise the risks.

Question 41

What are people worried about in terms of new products containing nanoparticles?

Answer 41

That they’ve been made available before the effects on human health have been tested properly.

We don’t know what the long-term impacts on human health will be.

For this reason, many ppl believe that products containing nanoparticles should be clearly labelled so they consumers can choose not to buy them.

Question 42

Nanoparticles in sun creams.

Answer 42

-Nanoparticles have been shown to be better than the materials in traditional sun creams at protecting skin from harmful UV rays

-They also give better skin coverage

-But it’s not yet clear whether the nanoparticles can get into your body, and, if they do, whether they might damage cells

-They might also damage the environment when washed away

Question 43

Name items that graphene is used in.

Answer 43

-solar panels
-batteries

Question 44

What are composite materials?

Answer 44

Materials that have things added to make them more useful.

Question 45

Which has a higher melting point: Graphite or methane? Explain why.

Answer 45

Graphite

Graphite is a giant covalent structure that has a higher melting point than methane (small covalent molecule).

This is because melting it requires you to break covalent bonds, rather than weak intermolecular forces