Question

5 shown here are cartoons of two different polymers. based on these cartoons, which polymer would you expect to be denser? which one would have the higher melting point? [section 12.8]

Answer 1

Answer: The correct answer for a) Linear polymer with high density and high melting point and b) branched polymer with low density and low melting point

As the image is not attached , so I think it should be following image .

In the image , there are two types of polymers present . One polymer is long an unbranched , while other polymer is short and branched .

Polymers : These are giant molecules or repeating chains of small molecules formed by linking small molecules together by Carbon- Carbon covalent bonds .They are also called as " Macro molecules " . The process of formation of polymers is known as polymerization . The small molecules or the repeating units of a polymer are known as Monomers.

Polymers are produced naturally and can be synthesized artificially . Example of natural polymer are proteins , DNA etc and Artificial polymer are polyethylene , backelite etc.

Polymers are of various type based on their structure , linear , branched , cross linked . ( Describing following types of polymers based on image )

A) Linear polymers : These are long straight chain polymers like long string of Carbon -Carbon chain . These polymers when form , they fold back themselves like strands of fibre or mesh . They form very strong polymers .

They have well packed structures, due to which they have high intermolecular force of attraction . These high intermolecular force of attraction provide them high tensile strength and high density and hence they will have high melting point . It will be very difficult to break them .

Examples : Polyethene [-CH₂-CH₂-]n

Hence it can be said that a) box contains linear polymers and have high melting points and low densities.

B) Branched Polymers : These are linear polymers but have branches at regular intervals . These branches are known as side chains . The branches can be small or very long group . Branches polymers are also known as Dendrimers.

Due to branching , they cannot be closely packed . Branching prevents chain from getting close enough or to pack closely . Due to which they have low intermolecular forces . Hence they have low density and low tensile strength .So they have low melting points as well .

Examples : Glycogen , starch etc .

Since in image b) we can see the polymers have mall branches they can be assigned as " Branched polymers " and they will have low melting points and low densities.