properties of bonds

Question 1

What are polymers?

Answer 1

Polymers are very large molecules, made by joining monomers, with atoms linked by covalent bonds.

Question 2

What are thermosoftening polymers?

Answer 2

special type of polymers; they melt/soften when heated.

There are no bonds between polymer chains. Strong intermolecular forces that ensure that the structure is solid at room temperature can be overcome with heating - polymer melts.

Question 3

What are giant covalent

substances? Give examples

Answer 3

• Solids, atoms covalently bonded together in a giant lattice.
• High melting/boiling points – strong covalent bonds.
• Mostly don’t conduct electricity (no delocalised electrons)
• Diamond, graphite, silicon dioxide.

Question 4

Describe and explain the

properties of allotropes of carbon. (DIAMOND)

Answer 4

Diamond
– four, strong covalent bonds for each carbon atom
– very hard (Strong bonds)
– very high melting point (strong bonds)
– does not conduct electricity (no delocalised electrons)

Question 5

Describe and explain the

properties of allotropes of carbon. (GRAPHITE)

Answer 5

– three covalent bonds for each carbon atom
– layers of hexagonal rings
– high m.p + b.p
– layers free to slide bc of the weak intermolecular forces between layers;
– soft, can be used as a lubricant
– conduct heat and electricity due to one delocalised ion per each carbon atom
»> Graphene - a single layer of graphite.

Question 6

Describe and explain the

properties of allotropes of carbon. (FULLERENES)

Answer 6

– hollow shaped molecules
 – based on hexagonal rings but may have
5/7 carbon rings
 – C60 has spherical shape, simple
molecular structure (Buckminsterfullerene)

Question 7

Describe and explain the

properties of allotropes of carbon. (NANOTUBES)

Answer 7

– cylindrical fullerene with high length to
diameter ratio
- High tensile (can be stretched w/o breaking) strength (strong bonds)
- good conductors of heat + electricity (deloc. electrons)

Question 8

What is metallic bonding?

Answer 8

Forces of attraction between a sea of delocalised electrons and the positive metal ions.

Question 9

Describe properties of

metals

Answer 9

• High melting/boiling points (strong forces of attraction)
• Good conductors of heat and electricity (delocalised electrons)
• Malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)

Question 10

What are alloys? Why are
they harder than pure
metals?

Answer 10

Alloys:

• mixtures of metal with other elements, usually metals
• different sizes of atoms distorts the layers, so they can’t slide over each other, therefore alloys are harder than pure metals

Question 11

What are the limitations of

the simple model?

Answer 11

There are no forces between spheres and atoms, molecules and ions are solid
spheres – this is not true

Question 12

What does the amount of energy
needed to change state from solid
to liquid or liquid to gas depend
on?

Answer 12

• The strength of the forces between the particles in a substance
• type of bonding and the structure of the substance.

> > > The stronger the forces between the particles the higher the melting point and boiling point of the substance

Question 13

A pure substance will melt
or boil at…? What about the
mixture?

Answer 13

A fixed temperature.

A mixture will melt over a range of temperatures.

Question 14

What are the three states of

matter?

Answer 14

Solid, liquid and gas