Polymers and Giant Covalent Structures (117)

Question 1

What are Polymers?

Answer 1

they are lots of small units, they are linked together to form a LONG MOLECULE that has repeating sections.

natural polymers include silk, hair, proteins and DNA, while synthetic (man-made) polymers include polyethylne, polypropylene and polyester

Question 2

How are all the atoms in a polymer joined together?

Answer 2

they are joined together by strong covalent bonds.

Question 3

How can you draw out a whole long polymer molecule (which can contain thousands or even millions of atoms)?

Answer 3

you can draw the shortest repeating section. This is called ‘the repeating unit’

(see diagram on page 117 of book)

Question 4

How do you find the molecular formlar of a polymer?

Answer 4

write down the molecular formula of the repeating unit in brackets, and put an ‘n’ outside. (see diagram on page 117 of book)

Question 5

What is the molecular formular of Polyethene?

Answer 5

the formular of the polymer is (C2H4)n (see diagram on page 117)

Question 6

The intermolecular forces between polymer molecules are larger or smaller than between simple covalent molecules, and why?

Answer 6

the intermolecular forces between polymer molecules are LARGER so more energy is needed to break them.

Question 7

What substance are polymers at room temperature?

Answer 7

solid at room temperature

due to the intermolecular forces between molecules are larger, so they need more energy to break them. this means most polymers are solid at room temperature.

Question 8

The intermolecular forces for polymer are still weaker than ionic or convalent bonds, why is this?

Answer 8

they generally have lower boiling points than ionic or giant molecular compounds

Question 9

What are ‘intermolecular forces’?

Answer 9

it is used to describe the forces of attraction BETWEEN atoms, molecules and ions when they are placed close to each other.

Question 10

In Giant Convalent Structures, how are all the atoms bonded to each other?

Answer 10

they are bonded by strong convalent bonds

Question 11

Do Giant Covalent Structures have high or low melting and boiling points, and why?

Answer 11

they have very high melting and boiling points as lots of energy is needed to break the covalent bonds between the atoms.

Question 12

Do Giant covalent Structures contain charged particles and electricity?

Answer 12

No they don’t contain charged particles, so they don’t conduct electricity. - not even when molten

(molten means especially of materials with a high melting point, such as metal and glass, liquefied by heat)

(apart from a few weird exceptions such as graphite)

Question 13

What Giant covalent structures for diamond and graphite and Silcon Dioxide made from?

Answer 13

diamond and graphite are made from carbon atoms only, and silicone dioxide (silca)

Question 14

explain what Diamond giant convalent structure forms?

Answer 14

Each carbon atom forms FOUR covalent bonds, in a very rigid giant covalent structure

see diagram on page 117

Question 15

Explain what giant covalent structure Graphite forms?

Answer 15

Each carbon atom forms THREE covalent bonds, to create layers of Hexagons. Each carbon atom also has ONE delocalised (free) electron

see diagram on page 117

Question 16

Explain the giant covalent structure SILICON DIOXIDE forms?

Answer 16

sometimes called SILCA, this is what sand is made of. Each grain of sand is one giant structure of silicone and oxygen

see diagram on page 117

Question 17

to melt or boil a simple molecular substance or a polymer, what will break to melt or boil the giant convalent substance?

Answer 17

only the weakish intermolecular forces need to be broken to melt the giant covalent substance, you have to break very strong covalent bonds

Question 18

The repeating unit of poly(chloroethene) shown below, what’s the molecular formular of poly(chloroethene)?

Cl      H
 |        |  -  C  -    C-
 |         |
H       H

Answer 18

(C2H3Cl)n

Question 19

Predict, with reasoning, weather diamond or poly(ethene) has a higher melting point (3 points)

Answer 19

To melt diamond you have to break the covalent bonds between atoms which are very strong (1 mark)

but to melt poly(ethene) you only have to break the weaker intermolecular forces which needs less energy (1 mark)

So diamond has a higher melting point (1 mark)

Question 20

What is a diamond formation?

Answer 20

diamond formation occurs when carbon deposits deep wihin the earth are subject to high temperature and pressure, they bond together to start growing crystals

Question 21

what is polyethene?

Answer 21

Polyethlene or polythene is the most commonly produced plastic. It is a polymer, primarily used for packaging.