1. 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 from random orientation addition polymers. When immersed in acetone, the polymers are rearranged into a crystalline structure with H to T arrangement so it is denser.

2. 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 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.

Not enough effective inter-molecular bonding due to less surface area, material not as strong and may be cut through.

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

HDPE is more spread out, has more surface area for london dispersion forces to attract each other polymer more strongly, and it is thus more resistant to being cut – Stronger inter-molecular forces.

3. 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.

No. Atoms in paper are unable to slide over one another and stretch when a force is applied, due to the type of inter-molecular forces – covalent bonding restriction. It cannot stretch and will break immediately after a great force is applied.

4. A Teflon ear bone, a Fallopian tube, or heart valve? A Gore-Tex implant for the face or to repair a hernia? Some polymers are bio-compatible and now used to replace or repair body parts.

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

2) Non-Toxic
4) Fast & Flexible

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 restore 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 properties of an ideal polymer for contact lenses include:
Water absorbing that has water current to transmit oxygen to eye through lens.
The difference in material depends on the type of polymer being used. The polymers are different because it contains nitrogen atoms in its structure unlike PMMA which does not contain nitrogen. Polyacrylamide is similar to the polymers used to make acrylic fibres for fabrics. When the polyacrylamide chains are cross-linked, the material absorbs water. Substances such as this are called hydrophilic.

The differences in properties can keep the lens soft and flexible. However, the high water content also makes the lens more fragile and reduces clarity of vision.

1.Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in the Ohio Valley. Noting this, this 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?
Burning of coal will result in forming smoke, dust and particulate matter that block out sunlight. Sulphur emission from burning coal form tiny droplets which form aerosols. Aerosols reflect sunlight instead of absorbing, this reduces 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.
SO dissolves in rainwater to form acid. Natural rain has pH of 5.3 so the SO₂ released from the burning of coal would make the rain more acidic with a  pH of 4.3 

 

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

a. Hang your laundry to dry it.
Bases from detergent evaporate, neutralize acid

b. Walk, bike, or take public transportation to work.
Less NOx emissions from cars/vehicles

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

Less hot, less places for N₂ and N0₂ to react to form NO

e. Buy locally grown produce and locally produced food.

Reduce the need to import food hence reducing the need for transportation so less pollutants are emitted.

 

3a. Give names and chemical formulas for five acids and five bases.

Acids

Hydrobromic acid (HBr)

Phosphoric acid (H₃PO₄)

Sodium hydroxide (NaOH)

Potassium hydroxide (KOH)

Magnesium hydroxide (Mg(OH)₂)

 

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

Acids: Conduct electricity in aqueous solution, taste sour, turn blue litmus paper red

Bases: Conduct electricity in aqueous solution, taste bitter, turn red litmus paper blue

 

4. 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?

Half of the acid deposition in eastern Canada came from American sources while the other half from its own country. Within Canada, there were domestic agreements starting with a declaration signed by the federal government and the seven provinces in establishing the Eastern Canada Acid Rain Program.  The goal was to limit deposition of sulphate precipitations to less than 20kg per hectare each year. Provinces agreed to cap SO₂ emissions at 2.3 million tonnes in order to achieve the 20kg limit. To address the other half  of deposition of sulphates, Canada and U.S signed a bilateral agreement called the Canada-US air quality agreement to solve the transboundary air pollution problem. Both countries had to work together to reduce SO₂ and NOx emissions. Since the 20 kg/ha/yr deposition target under the Eastern Canada Acid Rain Program could only protect moderately sensitive lakes, a new program was established – The Canada-Wide Acid Rain Strategy for Post-2000. All 26 federal, provincial and territorial Ministers of Energy and Environment had to commit to reducing  SO₂ emissions in order to protect lakes and forests and improve human health. They strive to achieve a deposition level of 8kg/ha/year.

It originates both inside and outside of Singapore. There is definitely acid deposition in Singapore due to our high amount of vehicles producing NOx and power stations, refineries, other industries such as oil fuel companies releasing SO₂ into the environment. However, acid deposition in Singapore is worsened when there is excessive burning of forests in Indonesia. The wind patterns can bring in the acid deposition resulting in haze within Singapore.

 

 

References:

http://wildsingaporenews.blogspot.sg/2009/09/native-species-in-singapore-may-be.html#.WMzDJCN941I

http://www.nea.gov.sg/anti-pollution-radiation-protection/air-pollution-control