Bonding, structure and the properties of matter - questions 16- rest of questions

Why do larger molecules have higher melting points than smaller molecules?

The intermolecular forces are larger in large molecules.

Why do most covalent structures nit conduct electricity?

They do not have delocalised ions or electrons.

What is a carbon allotrope?

The different physical forms that carbon can exist in.

Give 3 examples of carbon allotropes.

Diamond, graphite, fullerenes.

Describe the structure and bonding in graphite

Each carbon atom is bonded to 3 others, in hexagonal rings, arranged in layers, has delocalised electrons, weak forces of attraction between layers.

Why is graphite soft?

Weak forces of attraction between the layers so they can slide over each other.

Why can graphite conduct electricity?

Delocalised electrons can move through the structure.

What is graphene?

A single layer of graphite.

What is a fullerene?

Hollow cage of carbon atoms arranged as a sphere or tube.

What was the first fullerene discovered?

Buckminsterfullerine (C60) that has a spherical shape

Give 3 properties of fullerines

Lubricants, drug delivery, high tech electronics

What is a nano tube?

Hollow cylinder of carbon atoms.

Describe the structure and bonding in diamond

Each carbon atom forms 4 covalent bonds with other carbon atoms in a giant covalent structure.

Give 3 properties of diamond

Very hard, very high melting point, doesn’t conduct electricity.

Describe the structure of a pure metal

Layers of positive metal ions surrounded by delocalised electrons

Describe the bonding in a pure metal

Strong electrostatic forces of attraction entered metal ions and delocalised electrons

Name 4 properties of pure metals.

Malleable, high melting and boiling points, good conductor of electricity, good conductors of thermal energy.

Explain why metals have high melting/boiling points.

Lots of energy is needed to overcome strong electrostatic attraction between positive metal ions and delocalised electrons.

Why are metals good conductors of electricity?

Delocalised electrons are free to move through the metal to carry the charge

Why are metals good conductors of thermal energy?

Delocalised electrons are free to move through the metal and transfer the thermal energy

What is an alloy?

Mixture of a metal with atoms of another element

Explain why alloys are harder than pure metals

Different sized atoms disturb the layers, preventing them from sliding over each other

What is the diameter range of coarse particles?

Between 2500nm and 10,000 nm

Coarse particles are also referred to as first or PM_10, what does this mean?

Particulate matter up to 10 micrometers in diameter

What is the diameter range of fine particles?

Between 100nm and 2500nm

Fine particles are also known as PM_2.5 what does this mean?

Particulate matter up to 2.5 micrometers in diameter

What is the diameter range of nano particles?

Between 1nm and 100nm

Approximately, how many atoms are in a nano particle?

A few hundred atoms

Describe the surface area : volume ratio of nano particles

Have a very high SA:V

How is the surface area to volume ratio calculated?

Surface area to volume ratio = surface area/volume

How are nano particles different to their material in bulk?

They have different properties, e.g. gold nano particles have much lower melting point than the bulk material

Why are nano particles used as catalysts?

Have high SA:V ratio, meaning more surface is in contact with the reactants. This means tiny quantities are needed

Describe how nano particles are used in nano medicine

Tiny particles (e.g. fullerenes) are absorbed more easily by the body than most particles. This means they could deliver drugs right into the cells where they’re needed most.

Describe the use of nano particles in electronics

Some nano particles conduct electricity, so they can be used in electronics. E.g. they can be used to make really tiny memory chips that hold vast amount of data

Describe the use of nano particles in deodorant

Silver nano particles are added to some deodorants as they have antibacterial properties

Describe the use of nano particles in sun cream

Nano particles are being used in sun creams as they have been shown to be better than the materials in traditional sun creams at protecting the skin from UV rays. They also give better skin coverage.

State 2 disadvantages of using nano particles

The wash nano particles affect the body aren’t fully understood, unknown long term impacts on health. Nano particles may cause environmental damage.