Meeting 3

Date: 29th March 2017

Location: LT23

Time: 1.30pm

Duration: 3 hours

Team members who attended: All

Topics discussed (briefly):

Complete the online E-learning task together. 

Discuss the videos to be created.

Edit the blog.

Tasks to be done before the next meeting and who has been assigned/agreed on doing them:

Finish our video so that we can make final amendments.

Problems arising if any:

Plan of action: Everyone to do their part and meet up again next week.

Meeting 2

Date: 22nd March 2017

Location: LT23

Time: 3.00pm

Duration: 1 hour

Team members who attended: All

Topics discussed (briefly): Continue working and improving on our parts allocated for the blog

Tasks to be done before the next meeting and who has been assigned/agreed on doing them:

Finish up blog before next week’s meetup so we can discuss about the video.

Problems arising if any:

Plan of action: Everyone to do their part and meet up again next week.

Meeting 1

Date: 15th March 2017

Location: LT23

Time: 3.00pm

Duration: 1 hour

Team members who attended: All

Topics discussed (briefly): What is our topic exactly, allocate work to members

Tasks to be done before the next meeting and who has been assigned/agreed on doing them:

Everyone to start working on their individual parts for the blog

 

Problems arising if any:

Plan of action: Everyone to do their part and meet up again next week.

Implications to society

Oxygen is often heralded as one of the most important molecules known to man. It is involved in a wide array of reactions including combustion, rusting, and perhaps most importantly, respiration. Oxygen makes up about 21% of our atmosphere, and is usually abundant all around us in high enough concentrations to sustain human life, except above us. The reason for this is that the atmosphere thins with increasing altitude, and this is particularly relevant when it comes to the topic of commercial flights. While we usually pay no heed to the air we breathe in, there is in fact a lot of effort put into maintaining the air pressure of the cabins at an acceptable level (usually ~0.76atm). However, there are situations that could cause the air cabins to lose air pressure to the surroundings. In said situations, passengers have less than half a minute to react and utilise the deployed oxygen masks or risk passing out.

1. Oxygen masks are crucial for flight safety

Airplanes are pressurized to artificially keep the cabin at a lower altitude so that people can breathe without discomfort. However, without a pressurized cabin, the  air is too thin at high altitudes hence oxygen is too scarce for our body to function. The average person would pass out in about 15 to 20 seconds without the assistance  of an oxygen mask.

2. The development of this Chemical Oxygen Generator is safer for flight

Unlike diving tanks, where oxygen is compressed into a tank, oxygen is “stored” in a cocktail of chemicals located above each passenger seat.  In the event that there is a sudden loss of cabin pressure, oxygen masks will drop down from the panel above each passenger. The chemical mixture will only ignite to produce oxygen gas upon tugging of the mask. This method of production and delivery is more efficient and safer compared to compressed oxygen tanks.

 

3. The Chemical Oxygen Generator can be used in other environments


This production method can be modified to suit the environment where oxygen is needed. For example, submarines operated in a high pressure closed-circuit environment and hence, the chemical mixture has to be contain in a metal casing that is able to withstand high pressures.

 

References used:

The truth and myths about oxygen masks on airplanes

www.telegraph.co.uk/travel/travel-truths/truth-about-oxygen-masks-on-planes/amp/

AE 7

Unit 8- The World of Polymers and Plastics

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

Although it looks like a chemical reaction due to the large change in size, it is actually a physical reaction of dissolving. The acetone (the solvent) in the nail polish will cause the styrene (the solute) to dissolve. The large change in size is because styrofoam consists largely of air, thus, as the air escapes, only the small amounts of styrene dissolved in acetone are left. When the acetone evaporates, solid styrene is left.

This styrene could have air introduced into it again and become styrofoam afterwards.

Question 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.

LDPE is not strong enough to have a very high resistance to being cut.

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

Linear HDPE chains are arranged in a way that they are strong enough for this application. Using a thin layer of HDPE will enable it to be more flexible.

Question 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.

Plastic is a series of long chain polymers. When the piece of plastic is stretched, the molecules are aligned parallel to each other and facing in the direction of the pull. However, when the same pulling force is applied to a piece of paper, the paper tears rather than stretching as the cellulose molecules in paper are held far more rigidly in place, and are not free to become aligned. They are similar to the cross linked polymers and does not stretch.

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.

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

It should be non cytotoxic, stable for a long time of extended use, has low reactivity with body fluids and acceptable elasticity.

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.

Contact lenses are made from hydrogel, it absorbs water so as to transmit oxygen into eyes.

The contact lens is a device that covers part of the cornea, for such a device, it would be desirable if the material used allows oxygen to pass so that extended wearing will not harm the cornea while being able to absorb water ensures hydration of the covered portion of the cornea to a certain degree, increasing the comfort while wearing the lenses.

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 contact lenses were made of a type of plastic called poly methyl methacrylate (PMMA).

Since oxygen cannot pass through a PMMA contact lens, the only way for this vital element to reach the cornea was for tears to wash underneath the lens with each blink. In order for this blink-induced, tear-pumping action to occur, PMMA lenses had to be made relatively small in size. Also, there had to be a significant gap between the edge of the lens and the surface of the cornea.

These design characteristics made many people very aware of PMMA lenses on their eyes or caused discomfort that made wearing the lenses impossible. In some cases, these features also caused problems with PMMA lenses popping off the eye, especially during sports.

Most GP (soft) lenses incorporate silicone, which makes them more flexible than PMMA, thus the permeability-related design constraints that plague the hard lenses are largely overcome, allowing the soft lenses to actually be designed with comfort in mind.

Source: http://www.allaboutvision.com/contacts/rgps.htm 

AE 6

Unit 6- Neutralising the Threat of Acid Rain

Question 1

Mammoth Cave 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.

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

Coal contains varying amounts of sulfur, hence coal-fired plants will release SO2 gas as burning of sulfur in oxygen produces SO2 gas which is poisonous.

S(s) + O2(g) -> SO2(g)

Once in the air, the SO2 can react with oxygen molecules to form sulfur trioxide.

2 SO2(g) + O2(g) -> 2 SO3(g)

SO3 then reacts with water to form sulfuric acid.

SO3(g) + H2O(l) -> H2SO4(aq)

Poor visibility, which is haze, results from tiny droplets of liquid or solid particles suspended in air. Many molecules of sulfuric acid form tiny droplets. These droplets form aerosols that do not absorb sunlight but reflect it thus reducing visibility.

b.The NPCA reported “the average rainfall in the 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.

pH 4

Question 2

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.

Requires less energy compared to using a clothes dryer, hence reduces the need for power plants to produce electricity by burning coal.

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

Reduces gasoline used, cuts down on NOx emissions and thus reduces acidity of rain.

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

Consume less electricity and reduces the burning of coal by power plants.

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

Reduces heat loss, thus less electricity needed to heat up the hot water, and less need for power plants to burn coal.

e. Buy locally grown produce and locally produced food

Reduces NOx emissions from vehicles (e.g. planes, ship) that bring in imported food, thus reducing acidity of rain.

Question 3

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

Acids:

  1. Nitric acid HNO3
  2. Sulfuric acid H2SO4
  3. Hydrochloric acid HCl
  4. Carbonic acid H2CO3
  5. Hydrofluoric acid HF

Bases:

  1. Sodium hydroxide NaOH
  2. Ammonium hydroxide NH4OH
  3. Barium hydroxide Ba(OH)2
  4. Calcium hydroxide Ca(OH)2
  5. Lithium hydroxide LiOH

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

Acids:

  1. Turn blue litmus paper red
  2. React with reactive metals to produce hydrogen gas
  3. Sour taste

Bases:

  1. Turn red litmus paper blue
  2. Slippery feel when dissolved in water
  3. Bitter taste

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 the Singapore’s borders?

URLs:

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

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

http://www.grida.no/

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

Acid rain could cause Singapore’s remaining native species to become extinct at Singapore’s Bukit Timah Nature Reserve (Straits Times  ‘Native species may be wiped out by acid rain’ Sept 14 2009). However, NParks replied that the acidity of the streams may not be caused by acid rain as the streams could be naturally acidic, thus a conclusion cannot be made until more studies are done. 

Acid deposition could originate inside Singapore’s borders as there are many local emitters of sulfur dioxide such as motor vehicles, refineries, power stations, shipping and other industries, according to NEA. Sulfur dioxide and NOx emission contribute to acid rain.

Source: http://wildsingaporenews.blogspot.sg/2009/09/native-species-in-singapore-may-be.html#.WMo92Pl97ic

http://www.straitstimes.com/singapore/pushing-for-higher-air-quality