Q1) When Styrofoam packing peanuts are immersed in acetone (the primary component in some nail polish removers), they dissolve. If the acetone is allowed to evaporate, a solid remains. The solid still consists of Styrofoam, but now it is solid and much denser. Explain. Hint: Remember that Styrofoam is made with foaming agents.

Styrofoam is made initially with small spherical polystyrene beads made with foaming agents. Foaming agents are basically a material that facilitates the formation of foam. As such, the formation of styrofoam involves  polystyrene beads being heated with steam and left to cool down before heating it again within a mould. As such, styrofoam are made up of 98% air. Hence when it is dissolve in acetone, the air in the foam will get released, leaving behind the solid polystyrene which is more dense.

Q2) Consider Spectra, Allied-Signal Corporation’s HDPE fiber, used as liners for surgical gloves. Although the Spectra liner has a very high resistance to being cut, the polymer allows a surgeon to maintain a delicate sense of touch. The interesting thing is that Spectra is a linear HDPE, which is usually associated with being rigid and not very flexible. 

a. Suggest a reason why branched LDPE cannot be used in this application.

Branched HDPE may be too fragile and break under the high pressure exerted by surgical tools or the surgeon’s intricate hand manoeuvres. If the glove breaks, it can pose a great danger to the surgeon as the surgeon may be exposed to biohazardous material.

b. Offer a molecular level reason for why linear HDPE is successful in this application.

Linear polyethylene is normally produced using the monomer ethylene (C₂H₄), with molecular weights in the range of 200,000 to 500,000 or higher. While it is very flexible, it is still very tough. Its flexible nature makes it suitable for use as gloves for surgeons who need to make intricate hand movements very carefully, while its toughness protects the surgeon from contact with biohazardous material.

Q3) When you try to stretch a piece of plastic bag, the length of the piece of plastic being pulled increases dramatically and the thickness decreases. Does the same thing happen when you pull on a piece of paper? Why or why not? Explain on a molecular level. 

Papers are made of long fibres of cellulose which has 2 main kinds of bonds, mainly strong intermolecular forces such as hydrogen bonding between microfibrils of cellulose and weak intermolecular forces such as van der wall forces.Cellulose are actually made up of many glucose monomers that let the chain stretch out, nice and straight. Since the cellulose is a long polymer chain consisting of many glucose molecules, it forms many strong hydrogen bonds .Thus, it is hard to separate the cellulose apart therefore it is not possible to pull on a piece of paper.
Plastics on the other hand, are made of polyethylene.(LDPE). Such polymers have long molecules that lie side by side.As such, these molecules can uncoil and slide past each other, making the material flexible since it does not have intermolecular hydrogen bonds, only weak inter molecular forces like van der wall forces which are easy to break apart.

Q4) A Teflon ear bone, fallopian tube, or heart valve? A Gore-Tex implant for the face or to repair a hernia? Some polymers are biocompatible and now used to replace or repair body parts.

a. List four properties that would be desirable for polymers used within the human body.

1) Non-Toxic
2) Low Cost
3) Inert to Body Fluids
4) Durable

b. Other polymers may be used outside your body, but in close contact with it. For example, no surgeon is needed for you to use your contact lenses – you insert, remove, clean and store them yourself. From which polymers are contact lenses made? What properties are desirable in these materials? Either a call to an optometrist or a search on the Web may provide some answers. 

The first contact lenses were made from a polymer called polyacrylamide. Rigid gas-permeable lenses then became available. These lenses are a combination of PMMA, silicones and fluoropolymers. It has to be lightweight, non-toxic, permeable to oxygen and flexible.

c. What is the difference in the material used in “hard” and “soft” contact lenses? How do the differences in properties affect the ease of wearing of contact lenses?

Hard contacts lenses are made from PMMA, a material that is inflexible and does not oxygen to pass through, soft contact lenses on the other hand are made of Silicone, this materials allows for oxygen to pass through and is flexible, making soft contacts more comforting to the eye.

Q1) Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in Ohio Valley. Noting this, the National Parks Conservation Association (NPCA) reported that this national park had the poorest visibility of any in the country. 

a. What is the connection between coal-fired plants and poor visibility?

In Coal-fired plants, combustion occurs resulting in sulfur dioxide being produced. Sulfur dioxide contains sulfur particles that would hence result in poor visibility.

b. The NPCA reported “the average rainfall in Mammoth Cave National Park is 10 times more acidic than natural.” From this information and that in your text, estimate the pH of rainfall in the park.
The average pH of rain is approximately in the range of 6-7. Since the pH of the rain in Mammoth Cave National Park is 10 times more acidic and the decrease in every pH 1 results in an increase in concentration of hydronium ions by ten times. The pH of the rainfall of the park is approximately 5-6.

Q2) Here are examples of what an individual might do to reduce acid rain. For each, explain the connection to producing acid rain. 

a. Hang your laundry to dry it.

By hanging out your laundry to dry instead of using a dryer, we can save electricity and energy which may contribute to acid raIn. This is because any fossil fuel consumption, which we use for things like energy generation, heating, and transportation can lead to acid deposition which will lead to acid rain.

b. Walk, bike, or take public transportation to work.

This reduces transport related energy and fuel consumption and thus it can help reduce any emissions into the atmosphere which may contribute to acid rain. Since vehicles are powered by fossil fuels, these contribute to sulfur dioxide and nitrogen oxide which will cause acid deposition.

c. Avoid running dishwashers and washing machines with small loads.

Similar to (a), instead of running dishwashers and washing machines with small loads, hand washing these dishes or clothes will save electricity and energy and therefore reducing fuel consumption that will lead to acid deposition.

d. Add additional insulation on hot water heaters and pipes.

Adding insulation will ensure that heat will not escape so easily and thus this will reduce the energy used unnecessarily. Again, this will ensure lesser fuel is being used and it will mitigate the impact on acid deposition.

e. Buy locally grown produce and locally produced food.

Shopping locally will help reduce any transport related fuel consumption and emissions being released into the atmosphere. Since the fossil fuels used are huge contributors to the sulfur dioxide and nitrogen oxides that cause acid deposition, shopping locally can help reduce the impact of these on acid rain.

Q3) 

a. Give names and chemical formulas for five acids and five bases. 

b. Name three observable properties generally associated with acids and bases.

Q4) The concerns of acid rain vary across the globe. Many countries in North America and Europe have websites dealing with acid rain. Either search to locate one (“Canada, acid rain”) or use these links to websites in Canada, the UK, or Europe. What are the issues in Singapore? Does the acid deposition originate outside or inside the Singapore’s borders?

URLs: 

http://www.ec.gc.ca/

http://www.ukawmn.ucl.ac.ul/

http://www.grida.no/

http://www.nea.com.sg/

Many websites throughout the world set different standards in response to acid rain. In Europe, In Europe, the G.R.I.D Arendal provides articles related to acid rain and workshops done to counter it such as the Abidjan Convention Sustainable Seas pilot workshop.

Singapore takes the issue of acid rain seriously. The issues that Singapore faced would be the annual haze that happens due to the change in wind direction which can result in acid rain. Haze that originate from Indonesia will get redirected to Singapore. At the NEA website, they would provide hourly updates on the PSI levels and PM2.5 of different regions in Singapore. The public could access such data at the NEA website and get notified when the PSI and PM2.5 levels goes beyond the safe region.

Acid deposition originate both outside and inside the Singapore borders. As mentioned earlier, Haze from neighbouring countries like Indonesia contribute to the acid deposition which are outside the Singapore borders. Acid deposition can also originate within Singapore too.  One of Singapore’s main source of income comes from its chemistry industry which can also contribute to acid deposition in Singapore, especially if waste are disposed indiscriminately. Also, vehicles in Singapore produce NOx, which also contribute to acid deposition inside Singapore borders.

Canada

1. Canada created a federal-provincial team to devise a common solution ― the 1985 Eastern Canada Acid Rain Program. It established:

• A limit of 2.3 million tonnes of Sulphur Dioxide (SO2) in 7 provinces closest to its East, to be met by 1994 and maintained until 2000.
• 7 federal-provincial sulphur dioxide reduction targets for each province east of the Manitoba-Saskatchewan border to meet this regional cap (the first round of reductions were intended to roughly halve the sulphur dioxide emissions (SO2) in Eastern Canada from 1980 levels).
• A science and monitoring program.
• The basis for the federal government to seek reductions of flows of acid pollutants from the United States.

2. Canada signed the 1979 United Nations Economic Commission for Europe Convention on Long-Range Transboundary Air Pollution (UNECE LRTAP) with other European countries and the United States.
3. Environment Canada released its latest acid rain science assessment in 2004, which determined:

• A clear need for targeted additional sulphur dioxide reductions to protect more vulnerable areas, and aid the recovery of acid-damaged regions.
• A need to respond to the damage done to forests since they are now known to be vulnerable.
• A need to broaden the focus of activity to address a potential acidification problem in Western and Northern regions.

UK

In the 1980s, the UK was described by Scandinavian countries as “the dirty old man of Europe” due to high emissions of sulphur dioxide from industrial sources causing transboundary acid rain. Emissions of sulphur dioxide and oxides of nitrogen have since been reduced, although the UK remains a considerable emitter of acidic pollution compared to other European countries.

The 1998 Gothenburg Protocol requires the UK to reduce sulphur emissions by 85% and nitrogen emissions by 49% by year 2010 (from 1980 levels). To meet these requirements, emissions of sulphur dioxide in UK are being reduced, through the use of cleaner technology within the power generation industry, and the use of cleaner fuels and car engines in the transport sector.

While the acid rain problem in the UK has partially improved due to Margaret Thatcher’s government implementing aggressive measures to reduce sulphur emissions, nitrogen-related pollution still persists till today, which means both air and water quality are still being compromised.

Sources:

http://www.ec.gc.ca

http://www.enviropedia.org.uk/Acid_Rain/UK_Acid_Rain.php

http://www.telegraph.co.uk/news/earth/earthnews/9342276/Acid-rain-all-but-eliminated-over-Britain.html