Macromolecules

Question 1

What is the structure of polymers?

Answer 1

• the monomers in a polymer are joined together by covalent bonds between atoms
• however weak intermolecular forces (Van der Waal’s or hydrogen bonding) exist between the polymer molecules

Question 2

What are the properties of polymers?

Answer 2

-polymers are all different but they show a few general properties

• all poor conductors of heat and electricity
• unreactive
• exhibit high tensile strength, elasticity and ability to form fibers

Question 3

Why is the un reactivity of polymers both useful and problematic?

Answer 3

Their un reactivity makes polymers durable and able to safely contain and protect many substances.

However it also means that they persist in the environment for a long time

Question 4

What are the factors affecting properties of polymers?

Answer 4

1) reaction conditions
2) monomers
3) additives

Question 5

How do reaction conditions affect properties of polymers?

Answer 5

Temperature, pressure and catalysts affect the length and branching of the polymer chain

Question 6

How does the monomers affect the properties of the polymers?

Answer 6

The type of monomer affects the force between polymer chains

Question 7

How do additives affect properties of polymers?

Answer 7

Additives can “lubricate” polymer chains, join them together with cross-links or preserve them from decay

Question 8

What is addition polymerisation?

Answer 8

Addition polymerisation is the process by which one molecule (monomer) is directly added to another without any loss of any portion of the monomer to form very large molecules (polymer)

Question 9

Monomer VS polymer

Answer 9

Monomer: smallest unit from which the polymer is made

Polymer: long chain molecule with high molecular mass

Question 10

What is condensation polymerisation?

Answer 10

It is the process involving the combination of molecules with the elimination of small molecules such as water, hydrogen halide or ammonia between each pair of molecules

Question 11

How does hydrolysis take place in terylene and nylon?

Answer 11

Terylene contains an ester link that can be broken down by water molecules by breaking the C-O bond

Nylon contains an amide link that can be broken down by water molecules by breaking the C-N bond

Question 12

What are proteins?

Answer 12

Proteins are made up of a diverse group of large and complex polymer molecules, made up of long chains of amino acids

Question 13

Structure of amino acids

Answer 13

Amino acids contain both amine (NH2) and carboxyl (COOH) functional groups

The R group attached to the same carbon atom may vary. There are 20 amino acids used to make proteins and the simplest is glycine, where R=H

Question 14

How is Terylene converted back to monomers?

Answer 14

Terylene can be hydrolysed by reaction with dilute acid or alkalis. Polyesters are attacked readily by alkalis but much more slowly by dilute acid and insignificant with water

Question 15

How is nylon 6,6 converted back to monomers?

Answer 15

• can be hydrolysed by reaction with dilute acids or alkalis
• polyamides are readily attacked by strong acids but are more resistant to alkalis and insignificant with water

Question 16

What does hydrolysis of polyesters result in?

Answer 16

Hydrolysis either produces the monomers making up the polymer (acid hydrolysis)
or

carboxylate salt + alcohol if base hydrolysis is used

Question 17

What does hydrolysis of polyamides result in?

Answer 17

Acid hydrolysis: ammonium compound + Carboxylic acid

Base hydrolysis: carboxylate salt + amino acid

Question 18

How are proteins converted back to monomers?

Answer 18

1) reflux with hydrochloric acid (6 mol/dm3) During hydrolysis, the water molecule adds across the peptide bond, forming a mixture of the two amino acids
2) alkali solution (eg aqueous NaOH) above 100 degrees Celsius

Question 19

What are some uses of polyethene?

Answer 19

Typical plastic used to make plastic bags and cling film etc

Question 20

What are some typical uses of man-made fibers like nylon and Terylene?

Answer 20

They can be used in clothing, fishing lines, parachutes and sleeping bags etc

Question 21

What are some properties of plastics which make them widely used in place of natural materials?

Answer 21

• cheaper
• easily mounded into different shapes
• light, tough and water proof
• durable (resistant to decay, rusting and chemical reaction)

Question 22

What are some pollution problems faced by plastics?

Answer 22

1) they are non-biodegradable (cannot be broken down by microorganisms such as bacteria in the soil)
2) when plastics are burnt they give off poisonous gases

Question 23

What are macromolecules?

Answer 23

Macromolecules are very large molecules made up of many small units. Different macromolecules have different units and/or different linkages

Question 24

What are the conditions needed for addition polymerisation?

Answer 24

High temp and pressure, catalyst. Alkene to polyalkene