1) Styrofoam is almost 95% air (the foaming agent), and when dissolved in a solvent such as acetone, the reaction releases all the air that has been compressed in the styrofoam. What remains is only the styrene which makes it more solid and denser compared to its original form.

2a) Branched LDPE does not have a crystalline structure. It has a weaker intermolecular forces of attraction so the material is not as strong. Hence, it cannot have high resistance to being cut like HDPE.
2b) HDPE is linear giving a crystalline structure so that the attraction between molecules is stronger and has the necessary strength. At the same time, by using a thin layer as liners can reduce the rigidity so that it is more flexible yet the strength can be maintained which is important for surgical gloves.

3) When the piece of plastic is stretched, the strip narrows and neck down. The molecules become align parallel to each other and in the direction of the pull. This alteration of the three dimensional structure is not reversible, and if pulling continues, the plastic breaks.

When the same pulling force is applied to a piece of paper, the paper tear rather than stretching. The cellulose molecules in paper are hold far more rigid in place and are not free to aligned.

4a) They must not react with our bodily fluids, must be non-toxic to our bodies, have to be stable over time for the intended use and they would have to be easily implanted.
They would have to be non-toxic to the human body.

4b) Contact lenses are made up of either acrylamide, fluorosilicone acrylate or methyl methacrylate. Contact lenses that are made up of acrylamide are called soft lenses whilst contacts made from fluorosilicone acrylate or methyl methacrylate are called Rigid Gas Permeable (RGP) or Gas Permeable (GP) lenses. Soft lenses are desirable as the polyacrylamide lattice is polar hence highly hydrophilic. This is beneficial to those who frequently suffer with dry eyes that would make wearing contact lenses very uncomfortable. Flurosilicone acrylate was chosen as it has a high oxygen permeability and methyl methacrylate was chosen due to its ability to enhance optical quality and stability.

4c) The main difference is that soft contact lenses are made of silicone as compared to hard contact lenses which are made of PMMA, a non-gas permeable plastic. What this means is that the new property of the soft contact lenses allow oxygen to reach the human eye as compared to the hard contact lenses. the result is that soft contact lenses feel more comfortable for the human eye.