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AE 7: Polymers

1) Styrofoam contains a lot of air pockets. When dissolved in acetone, the air pockets are released and only the resin is left. That is why it is “solid and much denser”, because the air pockets, which makes it less dense, are no longer there.

2a) LDPE is not strong enough and can be easily broken or cut

2b) Weak but extensive dispersion forces allow the molecules to slip past one another, allowing flexibility. The linear arrangement also allows for greater strength.

 

A plastic molecule.

3) Plastic molecules are aligned in the same direction when stretched. When the pulling continues, it is stretched beyond its ultimate tensile strength and the structure eventually breaks. Paper, however, is brittle. The rigid cellulose molecules in paper are not able move around and change direction when stretched, hence they get torn and not stretched.

4a) Inert, durable, flexible, non-toxic

4b) Hard contact lenses are made of PMMA or poly(methacrylate). Soft contact lenses are made of HEMA, poly(hydroxyethyl methacrylate). Contact lenses need to have high oxygen permeability, refractive properties and hydrophilic. (Reference)

4c) Hard contact lens are easier to wear and clearer, but it is more uncomfortable. It is usually prescribed to astigmatism cases and to correct bi-focal problems. Soft contact lenses are more comfortable and stays in place better. Oxygen is allowed to pass through the contact lens to the cornea due to the flexibility of the soft contact lens when combined with water. (Reference)

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Application Exercise 6

1a)  Coal-fired plants produce smog, which prevents visibility.

China is one of the countries in the world whose cities has been hit by smog almost everyday. Photo: The Verge

1b) Normal rainfall has a pH of 5-5.5 (see here), so a rainfall 10 times more acidic would mean that it has a pH of 4-4.5.

2a) You will use less electricity, therefore you create lesser demand for electricity, and therefore, power plants will generate lesser electricity. This will bring down the amount of SOx released into the atmosphere.

2b) The amount of nitrogen oxide produced by the automobiles will be reduced.

2c) Less electricity is being used, and the water would be cleaner and less polluted from chemicals arising from the detergents and other chemicals. Less resources also will be used to clean that “dirty water”.

2d) Reduce electricity to heat the water, by preventing heat loss.

2e) Reduces transportation. But this answer is not always true, as some plants that are required for subsistence may not be native. Therefore, greenhouses must be built, which requires massive amounts of energy creation.

3a) Acids: Sulfuric acid (H2SO4), fluorosulfuric acid (HSO3F), nitric acid (HNO3), phosphoric acid (H3PO4) and fluoroboric acid (HBF4).

Bases: Lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), rubiclium hydroxide (RbOH) and cesium hydroxide (CsOH).

3b) Acids: Sour in taste, reacts with metals, turns blue litmus red

Bases: Bitter in taste, slippery when dissolved in water, turn red litmus blue

4) According to the Department of Environmental and Climate Change in Canada, Canada has taken several steps since the early 1980s (it has detected acid rain in the 1960s) to reduce its acid rain problem. Among these are:

Acid rain has devastating effects on the environment, among which is the acidification of freshwater lakes, which makes lakes it impossible for marine life to live there

– Cap the production of SO2 at 2.3 million tonnes in the seven Canadian easternmost regions, to be met from 1994 and maintained from 1994 to 2000.

– Work with the US government to reduce the flows of acid pollution from the US into Canada

– Signed the US-Canada Air Quality Agreement of 1991, which led to the monitoring of emissions, reduction of sulphur and nitrogen oxide emissions

In Singapore, we generally do not have acid rain. However, haze (air pollution) is a major problem in Singapore. Haze is created by the mass burning of forests in Indonesia. This is usually done at the start of the farming season, when Farmers burn the land to make the soil more fertile for the next batch of crops. Haze disrupts daily activities, reduces visibility and aggravates health issues for those who are particularly susceptible to air pollution.

Haze in Singapore. Photo: The Asian Parent