Application Exercise 7

  1. Styrofoam contains mostly air hence when it is released by dissolving it in acetone, it looks like the huge quantity of solid is dissolved into a smaller quantity of liquid and is more dense.

2a. LDPE is soft, stretchy and flexible. It will not be resistant to cuts.

2b. It is successful in this application as a thin layer of HDPE was used. This allows the gloves to be less rigid and more flexible. At the same time, HDPE is also orderly arranged, hence maintaining the strength and resistance to being cut.

3. This does not happen in paper. When the plastic is stretched, the 3D structure is altered whereby the molecules become aligned and move in the direction of the pull. This is because there are weak dispersion forces between the HDPE molecules and are easier to break.
On the contrary, paper tears when it is pulled. This is due to the cellulose molecules having stronger intermolecular forces of attraction between the molecules hence it is difficult for molecule to slip pass one another.

3a. It should be safe, biocompatible, cost effective and long lasting.

3b. Polymers such as polymethyl methacrylate (PMMA) are used. More commonly now is the use of Silicone-acrylate materials under trade names such as Kolfocon. Lenses that are comfortable, safe, inexpensive and permeable to oxygen are a few desirable properties.

3c. The difference is that in hard contact lenses, PMMA is used. It is a rigid non permeable plastic. In soft contact lenses, silicone is used. Silicone is more flexible and comfortable to the user during long hours of wear. Silicone also allows oxygen to reach the eye hence it is healthier and safer compared to PMMA.

Application Exercise 6

1a. Sulfate particles formed from sulfur dioxide which is produced by the coal fired plants. This results in the poor visibility.

1b. Normal rain is about pH5.3, since it is 10 times more acidic than natural, the rainfall in the park will have a pH of 4.3.

2a. By hanging it to dry, a dryer does not have to be used. This saves more electricity which is generated by burning of fossil fuels (in the US). With less burning of fossil fuels, less pollutants are produced and present in the atmosphere hence reducing acid rain.

2b. By taking public transport, less cars are used. This reduces emission of NOx and thus reduces the formation of acid rain.

2c. This is to save electricity as the machines will be used less frequently.  Electricity is generated by the burning of fossil fuels. With less burning of fossil fuels, less pollutants are produced and present in the atmosphere hence reducing acid rain.

2d. By insulating the pipes and heaters, we reduced the heat loss to environment. This decreases the amount of energy required to maintain the heat hence saving electricity by using fossil fuels. Burning of fossil fuels contribute to the formation of acid rain.

2e. By buying local food, our carbon footprint is reduced. This results in lesser pollutants formed and hence reduction of acid rain.

3a. Hydrochloric acid, HCl ; nitric acid, HNO3 ; sulfuric acid, H2SO4; carbonate acid, H2CO3 ; Phosphoric acid, H3PO4

sodium hydroxide, NaOH ; lithium hydroxide, LiOH ; magnesium hydroxide, Mg(OH)2; potassium hydroxide, KOH ; ammonia, NH3

3b. Acids are sour while bases are bitter. Acid turns blue litmus red while base turns red litmus blue. Both reacts with metals.

4. Some issues found in Singapore are the formation of acid rain and production of haze. Some examples are the corrosion of the National Museum of Singapore. Native species in Singapore including frogs, crabs and fishes may be wiped out by the acid rain. The haze is caused by the burning of biomass in neighbouring countries hence the acid deposition originates mostly from outside Singapore’s borders. Some acid deposition also originates from inside Singapore’s borders as pollutants are produced by automobiles and factories.

 

Application Exercise 5

  1. Ways to purify water while hiking:
    a. Heating the collected water and collecting the condensed watero04-water_stillBoiling helps to remove microorganisms by killing them however it cannot remove any chemical contamination of the water. Boiling cause environmental pollution as it can release carbon monoxide and soot to the environment.

    b. Purify water using iodine.
    downloadLike boiling, iodine helps to remove microorganisms but cannot remove any chemical contamination. It takes a shorter time compared to boiling however tablets are more costly. Additionally, it is not advisable to take this in the long run as there are adverse health effects for pregnant women and people with thyroid conditions.

    c. Filtering water with a filtering device.

    Filtration can remove many microorganisms that cannot be removed by iodine or boiling. It also takes the fastest amount of time. However it is more costly thank heating or using iodine.

  2. Desalination techniques such as reverse osmosis and distillation are expensive even though they are effective.
  3. a) Sources include corrosion of lead pipes, solder drinking fountains and water tanks.b) It does not contribute to the elevated lead levels as the drinking and research waste pipes should be separated hence the by products do not go into the water source.
  4. Water soluble vitamins are polar whereas fat soluble vitamins are non polar. To dissolve in water, the molecules have to be polar to favour hydrogen bonding with water molecules. Whereas, for fat soluble vitamins, they have to be non polar to form hydrophobic interactions with the fat molecules to dissolve in them.

Application Exercise 4

  1. The atmosphere retains the heat so it still trapped in our surroundings. Molecules such as CO2 and H2O trap heat in our atmosphere.pollution-bad_fbd596fd1a506e77
  2. Global warming has to do with the temperature change not climate change. Having cooler seasons like winter does not mean that the region is getting cooler.  Climate describes the typical and average weather a region will have over a period of time. Most of the time, climate is used for statistics about earth’s temperature and whether it’s getting warmer or colder.
  3. It heated up the air around the machine, causes diseases in the operators of the radar and the absorption of the microwave through water would interfere in detecting other objects.
  4.  It will not be dependent on the geography. Most people are concerned about the air quality in the short run. The ozone depletion is too distant for people to be as concerned.global-warming

Application Exercise 3 8th Feb

1a. The reaction is exothermic as heat is given off when the charcoal burns.

1b. The reaction is endothermic as water absorbs heat from the skin allowing it to evaporate and thus cooling the skin.

1c. The reaction is endothermic as ice absorbs the necessary heat which allows it to melt.

2. For a good explosion to occur, the bond energies of the products have to be larger than those of the reactants. This will lead to a negative energy change. The larger the energy change, the more exothermic the reaction will be.

3. Temperature indicates the direction of the heat flow whereas energy is a form of energy. Heat flows from an object at high temperature to one with lower temperature. An example would be a cup of hot water. Spilling a cup of hot water on yourself would hurt much more than spilling a drop of hot water on yourself even if both the cup and the drop of water are of the same temperature.

4a. The gasoline has the same characteristic as amixture made up of 98% of isooctane and 2% of n-heptane.  As a ‘premium’ gasoline, it has a higher octane rating than other blends sold at gasoline stations and is more resistant than these lower octane rating blends.

4b. Rating does not provide any information with regard to whether the fuel contains oxygenates.