Unit 4 Chapter 13: Macromolecules - polymers, proteins, and carbohydrates

Question 1

Polymer:

Answer 1

covalent molecular substance composed of many small molecules (monomers) joined together

Question 2

Monomer:

Answer 2

smaller molecule that reacts with another monomer (either of the same or different compound) to form a polymer

Question 3

Addition polymers:

Answer 3

must be unsaturated compounds (contain a double bond)

Question 4

Low Density Polyethene (LDPE) properties (out of 8)

Answer 4

• Produced with high temperatures and pressure
• Polymer forms too rapidly for molecules to be neat and symmetrical
• More branching –> molecules cannot pack as closely together –> weaker dispersion forces
• Low density
• Relatively soft
• Low melting point
• Non-crystalline
• Opaque, non-conductor

Question 5

High Density Polyethene (HDPE) properties (out of 7)

Answer 5

• Formed under low pressures using transition metal catalysts (Ziegler-Natta catalysts)
• Fewer branches –> more tightly packed –> stronger dispersion forces
• High density
• Hard
• Relatively high melting point
• Crystalline sections

Question 6

Longer chain length =

Answer 6

higher melting point

Question 7

Isotactic:

Answer 7

all side groups are on one side of the polymer chain

Question 8

Atactic:

Answer 8

side groups are randomly distributed on either side of the polymer chain

Question 9

Syndiotactic/Syntactic:

Answer 9

side groups are on regularly alternating sides

Question 10

Common addition polymers:

Answer 10

Teflon, acrylic, polystyrene, Perspex

Question 11

Condensation polymers:

Answer 11

formed when molecules with two functional groups meet and react together, eliminating a small molecule (usually water)

Question 12

Common condensation polymers:

Answer 12

nylon, polyester, starch

Question 13

Common characteristics of most polymers (out of 5):

Answer 13

• High resistance to chemicals
• Thermal and electrical insulators (non-conductors)
• High strength-to-weight ratio
• Can be moulded into variety of shapes
• Mostly derived from petroleum

Question 14

Thermoplastic polymer:

Answer 14

softens when heated (can be reshaped and more easily recycled) as they have no strong bonds between polymer chains

Question 15

Thermosetting polymer:

Answer 15

chars when heated due to strong covalent bonds between polymer chains (cross-links) which mean they do not melt and are difficult to reshape and recycle

Question 16

Cross-links:

Answer 16

strong covalent bonds between polymer molecules, which overall limit movement, are rigid, hard, and heat-resistant

Question 17

Elastomers:

Answer 17

have a few cross-links which allows the polymer chains to slide past each other when stretched, but return to its original position once released

Question 18

Crystallinity:

Answer 18

percentage crystallinity is a measure of the relative amounts of crystalline (ordered) regions and amorphous (disordered) regions in the material

Question 19

Factors affecting physical properties of polymers (out of 6):

Answer 19

• Polarity of side groups in the polymer chain
• Use of more than one monomer (copolymers)
• Polymer chain length
• Extent of branching (e.g., LDPE and HDPE)
• Arrangement of side groups in chain
• Inclusion of additives (e.g., plasticisers)

Question 20

Copolymer:

Answer 20

polymer made from more than one different monomer

Question 21

Plasticisers:

Answer 21

organic molecules used to soften plastic by forcing the molecules slightly further apart and weakening the dispersion forces which makes them more flexible

Question 22

Advantages of polymers (out of 7):

Answer 22

• Available in large variety
• Biologically inert/chemically-resistant
• Easy to mould
• Low density
• Good mechanical strength
• Properties can be modified
• Many can be recycled

Question 23

Disadvantages of polymers (out of 4):

Answer 23

• Many derived from petroleum
• Microorganisms cannot synthesise (breakdown) synthetic polymers
• Thermoplastic polymers have low thermal stability
• Thermosetting plastics are hard to recycle and may produce toxins when burnt