Unit 7: The World of Polymers and Plastics

This week, we covered Polymers and Plastics.

Here are our answers to AE 7


Question 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 consist of Styrofoam, but now it is solid and much denser. Explain. Hint: Remember that Styrofoam is made with foaming agents.

Acetone dissolves the polymer, allowing the gas of the foaming agent to escape.The volume of the polymer decreases and the polymer is more dense because the gas has been removed.


Question 2

Consider Spectra, Allied-Signal Corporation’s HDPE fiver, 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.

  1. suggest a reason why branched LDPE cannot be used in this application
  2. Offer a molecular level reason for why linear HDPE is successful in this application.

LDPE cannot be used because it is weaker than HDPE. This is because LDPE has more branches in the chemical structure, leading to there being multiple points of weakness.

HDPE has molecules that are packed closely in a linear fashion, giving it strength. The thin sheets allow room for flexibility.


Question 3

When you try to stretch a piece of plastic, 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, it does not.

For plastic bags, the polymer chains interact with each other using Van der Waal’s force, which is weaker. The molecules become aligned parallel to each other and in the direction of the pull. 

Cellulose is composed of covalent bonds between glucose branches, causing it to be very strong.


Question 4

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.

  1. List four properties that would be desirable for polymers and used within the human body
  2. 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.
  3. What is the different in the material used in “hard “ and “soft” contact lenses? How do the differences in properties affect the ease of wearing contact lenses?

It is stable over time of intended use, non-toxic, low-cost, and lacks solubility in body fluids

Polymethyl methacrylate (PMMA). It is non-toxic, permeable to oxygen, easy to wear, inexpensive, able to conform to the shape of the eye, and easily cleaned if not disposable 

Hard lenses are made of PMMA. Soft lenses are made of silicon which. This leads to soft lenses being more comfortable.

Unit 6: Acid Rain

This week, we talked about acid rain in class.

Here are our answers of AE6.


Question 1

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

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

Coal-fired plants release sulphur dioxide, creating sulphate particles that are responsible for poor visibility in the Park.

Normal rain has PH range 5 – 6, so if rainfall in this park is 10x more acidic, OH must be 4-5.


Question 2

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

  • Hang your laundry to dry it.
  • Walk, bike, or take public transportation.
  • Avoid running dishwashers and washing machines with small loads.
  • Add additional insulation to hot water heaters and pipes.
  • Buy locally grown produce and locally produced food.

By hanging laundry to dry, the dryer is not used. Thus, no electricity is used. This leads to 0 fuel consumption at power plants and hence lower SOx production.

Since there is lower automobile use, there is lower fuel consumption and combustion, and hence, lower NOx production.

By running dishwashers and washing machines only when there are full loads, there is lower electricity usage, which translates to lower fuel consumption at power plants and hence lower SOx produced

Additional insulation prevents excessive heat loss from water heaters and pipe. Less energy used to keep water hot, and less electricity is used, leading to lower fuel consumption at power plants and lower SOx production.

By consuming more locally produced goods, we would consume fewer goods produced elsewhere. This reduces the need to transport products over long distances, thus reducing the usage of container ships, aeroplanes and trucks for transportation. This results in lower rates of fuel combustion by vehicles and thus lower NOx production.


Question 3

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

Acids:

Hydrochloric Acid (HCl) — Nitric Acid (HNO3) — Sulphuric Acid (H2SO4), — Hydrobromic Acid (HBr) — Phosphoric Acid (H3PO4).

Bases:

Lithium Hydroxide (LiOH) — Sodium Hydroxide (NaOH) — Potassium Hydroxide (KOH) — Rubidium Hydroxide ( RbOH) — Calcium Hydroxide (Ca(OH)2).

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

Both are corrosive.

Both produce effervescence when in contact with water.

Both change the colours on litmus paper. Acids turn litmus paper red while bases turn litmus paper blue.


Question 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 of Singapore’s borders?

The issues we face are: Haze and Acid Rain

The acidity of the water comes from sulphur dioxide and nitrogen oxides in the atmosphere – from industrial pollutants and lightning, for example, – that dissolve in rain water, which then falls into streams and other bodies of water.

Acid deposition originates from both inside and outside. However, the bulk of the acid deposition in Singapore originates from outside of Singapore’s borders.

There is strict regulation of pollution and carbon emission in Singapore. Ocean and wind currents bring pollution and acid deposition from other countries to Singapore. Most of the surrounding countries have fewer restrictions on their production industries, allowing for greater rates of acid deposition in Singapore.