1. When polymer is dissolved, gas will be liberated, allowing the polymer to engage in a more efficient and lower energy configuration, hence becoming denser.
2. a) The intermolecular forces between LDPE molecules are too weak to meet the requirements.
b) HDPE consists of linear polymers that are engaged in London forces between one another. When cutting the polymer, one essentially is breaking the covalent bonds within the polymer molecule instead of going against the much weaker London forces. Thus, it would have a high resistance against being cut.
3. Plastic is made up of LDPE, and when it is stretched, the molecules will “slide” past one another, so it narrows. They become aligned parallel to the direction of stretch, and the process is irreversible. As the pulling continues, the intermolecular forces finally give out and it breaks.
One the other hand, paper is made of cellulose, which is held together much more rigidly. So, when they are stretched, themolecules do not “slide” past one another, and they just tear.
4. a) Polymers to be used within the human body should fit certain requirements. Firstly, the materials used should be non-toxic to the human body. The polymers used could be placed within the body for extended periods of time, any toxic substances could have terminal consequences on the human body. Next, The polymers used should be stable over the time of intended use, unable to react with the substances around it. Next, the polymers should be cost efficient for easy access for the general public. Lastly, polymers used should not be soluble in the medium of intended use.
b) Desirable properties to be used in contact lens polymers should be non-toxic, easily permeable by oxygen, non irritanant materials and inexpensive in cost. The material used should also be easy to clean to facilitate individual usage.
Some examples of polymers used in modern soft contact lens is silicone hydrogel while hard contact lenses are made using harder polymers, but still thin enough to allow oxygen to reach the eye.
c) Hard contact lenses uses PMMA (Polymethyl methacrylate) a harder polymer than that used inside soft contact lenses. Soft contact lenses uses silicone material to make it more comfortable to wear. Soft lenses are typically more breathable and flexible, making it more comfortable, but it is also more fragile in nature, making it more useful for short term wear.