Unit 2: 2 - Structure and Properties

Question 0

Can ionic compounds conduct electricity in solid state?

Answer 0

No, only in liquid form.

Question 1

Why do ionic solids have high melting points?

Answer 1

They have very strong electrostatic forces of attraction in ionic bonds so this holds them together.

Question 2

Why can ionic compounds which are molten or in a solution conduct electricity?

Answer 2

As the ions can move around, they can carry electrical charge.

Question 3

What are intermolecular forces?

Answer 3

Intermolecular forces are very weak forces of attraction between molecules. These forces are overcome when a molecular substance melts or boils.

Question 4

What is the general rule for the size of intermolecular forces?

Answer 4

The bigger the molecule, the bigger the forces. Small molecules like H2 have the weakest intermolecular substances so are gas at room temperature. The bigger molecules like C6H14 have stronger forces of attraction so may be liquid at room temperature.

Question 5

What is another name for giant covalent structures?

Answer 5

Macromolecules

Question 6

What is a major property of a giant covalent structure and why?

Answer 6

High melting/boiling point. As every atom is joined to multiple other atoms (e.g. In diamond) it is very hard to separate all these forces therefore it takes a lot of energy.

Question 7

Why is diamond so hard?

Answer 7

Every carbon atom is covalently bonded to 4 others in a 3D structure, making it hard and transparent.

Question 8

Why does graphite conduct electricity (and heat)?

Answer 8

When carbon atoms covalently bond with each other an electron is delocalised. This can carry electrical energy.

Question 9

Why is graphite slippery and grey?

Answer 9

Carbon atoms in graphite are joined to 3 others in a 2D structure, forming layers which slide over each other.

Question 10

What are fullerenes made of?

Answer 10

Carbon

Question 11

How are fullerenes arranged?

Answer 11

They are large molecules made with hexagonal rings of carbon atoms. The rings join together to make cage-like shapes, some of which are nano-sized.

Question 12

Name 3 uses of fullerenes

Answer 12

Drug delivery into the body, lubricants and catalysts (also reinforcing materials).

Question 13

Why are pure metals malleable?

Answer 13

The atoms can easily slide over each other without breaking allowing them to form a new shape.

Question 14

What uses do malleable metals have?

Answer 14

Wires, rods, sheets, tin foil etc.

Question 15

What is an alloy?

Answer 15

An alloy is a mixture of metals or a metal mixed with other elements.

Question 16

Why can alloys be more useful than pure metals?

Answer 16

Alloys distort the layers so therefore can make them harder (e.g. Steel is harder than iron). Also, they can be harder to corrode, and shape memory alloys will revert to their original shape after being heated, and therefore are useful in things like dental braces.

Question 17

Why are metals good conductors?

Answer 17

Metal lattices have lots of delocalised electrons which carry electric charge.

Question 18

What is a thermosoftening polymer?

Answer 18

A polymer that melts or softens easily when heated.

Question 19

What is a thermosetting polymer?

Answer 19

A polymer which does not melt or soften when heated.

Question 20

Why does high density and low density poly(ethene) have different properties?

Answer 20

High density and low density poly(ethene) were made under different conditions and with different catalysts, so therefore HD has a higher melting point and is stronger than LD.

Question 21

Give an example of a thermosoftening polymer

Answer 21

Poly(ethene)

Question 22

Give the molecular structures of thermosoftening polymers

Answer 22

In thermosoftening polymers, the polymer chains are tangled together, so when heated they fall apart from each other and are easily moved, as the intermolecular forces are weak.

Question 23

Give the molecular structures of thermosetting polymers

Answer 23

When formed, thermosetting polymers form cross-like links with each other and form covalent bonds, which are hard to break.

Question 24

What is a monomer?

Answer 24

A monomer is a single part of a polymer, which can join together to create a polymer.

Question 25

What is a polymer?

Answer 25

A polymer is an extremely long chain of monomers. It is given with the name poly before the monomer that is is made of. E.g. Poly(ethene) is made of ethene.

Question 26

How do we write the formula of a polymer?

Answer 26

H H
    |   |
-[-C-C-]-
     |   |    n
    H H

Question 27

How long is a nanometre?

Answer 27

1 billionth of a metre (10^-9m)

Question 28

What are the risks associated with using new technology like nano particles?

Answer 28

There could be risks to the environment and our health if they were used too much.

Question 29

Give 3 uses for nano-particles

Answer 29

Highly selective sensors, efficient catalysts, new coatings, new cosmetics and to give construction materials special properties.