AE 9 (5 Apr ’17)


a) C5H9N3


c) N-H (can form hydrogen bonds with water)


a) C16H21N3

b) The similarities are: a two-carbon chain with a nitrogen at the end and a three-atom sequence of N-C-N, the spatial placement of these pieces, and the flat 5-ring of histamine can also be considered similar to the flat 6-ring of the antihistamine.

3. Drugs that produce a physiological response in the body: b, d

Drugs that inhibit the growth of substances that cause infections: a, c, e, f


a) Since becoming widely available, problems have been found in certain dietary supplements. The causes of this include how herbs are sometimes contaminated with germs, pesticides, or heavy metals that are toxic, or are accidentally contaminated by the growth of another plant within the herb’s population which could lead to cases of mistaken identity in similar looking plants. Other causes include how the labels on these supplements do not add up to what is actually in them; supplements might contain more or fewer ingredients as listen on the label, or the amount might be different from that stated on the label. Furthermore, some herbal suppliers (those who grow, harvest, or sell the crops) may mix or even substitute their crops with less expensive or more readily available plants for profit purposes. Given the global market, all of these problems can make it harder for a company to be sure that what they thought they were buying to make supplements is actually the herb they wanted.

b) All Chinese Proprietary Medicines (CPM) i.e. products in the finished dosage forms (e.g. tablet, capsule, liquid) are regulated by the Health Sciences Authority (HSA) and must comply with a set of safety and quality criteria before they are allowed to be sold in Singapore. In addition, CPM dealers (importers, wholesale dealers and manufacturers) are also required to be licensed by HSA.

AE 7 (22 Mar ’17)

1. As acetone dissolves the polymer, the gas of the foaming agent can therefore escape. This leads to the collapse of the polymer on itself, making it more dense due to the removal of the gas.


a. It does not have the strength required to be used.

b. HDPE molecules need to be lined up in a way that produces the amount of strength required. Sufficient flexibility can be obtained by using a thinner linear HDPE.

3. No, it does not happen to the piece of paper. When pulling force is applied to a piece of paper, the paper tears. This is due to cellulose molecules in paper being held more rigidly in place as compared to in plastic. Therefore, in comparison, when a piece of plastic is stretched, its molecules are free to align themselves parallel to each other and in the direction of the pull. However, once the plastic has been pulled to alteration, the structure is no longer reversible.


a. 1) Stable, 2) non-toxic, 3) lack of reactivity in body fluids, and 4) does not dissolve in body fluids.

b. There are different types of contact lenses which each use different types of polymers. One of the earliest polymers used for lenses is Polymethyl methacrylate (PMMA). It was used for its rigid gas permeable (RGP) property to make lenses.
Nowadays, silicone-acrylate materials are used (more commonly known by its trade name, Kolfocon). These RGP polymers contain fluorine, thus altering the structures slightly to form fluoro-silicone-acrylate polymers and fluoro-silicones.
As for soft lenses, Polymacon is usually used. Polymacon is a polymer of 2-hydroxyethyl methacrylate (HEMA). Other such methacrylates include hioxifilcon and methafilcon.

The properties that are desirable from these materials include their being non-toxic, inexpensive, comfortable to wear and their permeability to oxygen. Furthermore, their ability to be flexibly shaped to the shape of one’s eye as well as to be cleaned easily is desirable.

c. As mentioned above, hard contact lenses are typically made of PMMA, an RGP plastic. The soft contact lenses in comparison are made of silicone, which is flexible and allows oxygen to reach the eye. Because of these properties, the soft lenses tend to be more comfortable.

AE 6 (15 Mar ’17)


a) Coal-fired plants release sulfur dioxide, which forms sulphate droplets which reflect away sunlight, thus reducing visibility.

b) Normal rain has a pH range of 5-6. This means that if the rainfall is 10x more acidic, the pH range will fall in between 4-5.


a) Less energy is required for hanging laundry in contrast to the amount required for operating a clothes dryer. If an electric dryer is in use, cutting down on energy use will mean that the power required will be decreased. Power companies will therefore have to burn less coal to produce electricity.

b) These options reduce the amount of energy sources used. They cut down on NO emissions, therefore lowering their contribution to rain acidity.

c) Similar to part a); less energy use in the form of electricity is required, thus reducing coal burning.

d) Saves energy by not allowing heat to dissipate into the surroundings, therefore decreasing the need for increased heating. Not insulating pipes will also heat up the air, increasing in the production of NO.

e) Importing food from overseas wastes cost of transportation that run on power such as coal and gasoline. Reducing imports/exports will thus lead to less use of coal and gasoline.

3. a)

Acids Bases
HCl (hydrochloric acid) LiOH (lithium hydroxide)
HNO3 (nitric acid) NaOH (sodium hydroxide)
H2SO4 (sulfuric acid) KOH (potassium hydroxide)
HBr (hydrobromic acid) Ca(OH)2 (calcium hydroxide)
HI (hydroiodic acid) Ba(OH)2 (barium hydroxide)

b) Acid tastes sour, turns blue litmus paper red, and releases carbon dioxide from carbonates. Bases taste bitter, turns red litmus paper blue, and have a slippery feel in water.

4. One of the biggest issues in Singapore currently is the haze. The issue stems from Indonesia’s forest fires. Relatively high concentrations of SO4(2-), NO3(-), and NH4(+) was seen during periods of burning. This was attributed to long residence time of air masses, which led to progressive gas to particle conversion of biomass burning emission components. The acid deposition originates outside Singapore borders as the ions are produced from the Indonesian’s forest fires.

AE 5 (22 Feb ’17)

  1. Water can be purified by 1) boiling, 2) iodine, 3) sip or squeeze water filters, etc.
    1) is a traditional method of water purification as it kills germs/microorganisms but it requires time and may not effectively remove chemical contamination. Furthermore, boiling requires fuel and might therefore release soot and CO2 into the environment.
    2) is an easy and effective short-term method (but should not be used long-term!) Similar to boiling water, iodine does not remove chemical contamination despite killing microorganisms.
    3) this is an example of a filtering device; it does not use any chemicals int the process and at the same time can remove microorganisms not killed by boiling or iodine. These are however, the most expensive option.
  2. Distillation and reverse osmosis are the two most common desalination techniques. Both require energy to remove salts from seawater, hence expensive – this is why they are not used more widely to produce potable drinking water.
  3. a) a likely major source of lead in the drinking water is from the lead pipes in the building; corrosion – a dissolving or wearing away of metal caused by a chemical reaction between water and the plumbing
    b) While it is theoretically true that research/experiment materials (including chemicals and lead compounds) should not be flushed down the drain/sink, in reality chemicals and compounds such as lead might still be flushed down the sewage and into the drinking water – however, this should not account for a majority of the lead levels in the drinking water.
  4. Only water-soluble vitamins would be expected to be polar molecules. Although a fat-soluble vitamin will often have individual polar bonds or small regions of the molecule, this is out-weighed by nonpolar sections. Polar covalent bonds attracted to water through hydrogen bonding may allow the molecules to dissolve in water, while nonpolar covalent bonds favour interactions with the nonpolar chains in lipids.


AE 4 (15 Feb ’17)

  1. The earth does not cool rapidly due to the atmosphere retaining much of the emitted heat energy. This is despite the fact that the amount of energy emitted is more than double the amount received.
  2. We decided that the statement in the picture is incorrect and unjustified. We believe that it is meant to make fun of those who remain ignorant to global warming, as well as remain unaware of the differences between weather and climate. The existence of seasons (such as winter, that are cold) does not mean that the earth is getting cooler. Furthermore, the main difference between weather and climate is the measure of time; this refers to how climate describes weather over a long time whereas weather remains as a short-term explanation of the atmospheric condition during a short period of time.
  3. It was unsuccessful because the absorption of the microwave radiation by water in the atmosphere interfered with the detection of the objects.
  4. For our group, we chose air quality for the short-term consequence. This is because it directly affects us (eg. haze in Singapore – unable to go out without wearing masks/having to close the windows/etc.). As for the long-term consequence, we chose stratospheric ozone depletion. This is due to the fact that it is linked to global warming, in that ozone depletion limits the absorption of harmful ultraviolet rays. The ozone layer act as a filter to protect us from the harmful ultraviolet rays, therefore, the thinning layer of ozone in the long run will prove harmful to us.

AE 3 (8 Feb ’17)

  1. a)Exothermic. A charcoal briquette releases heat as it burns.
    b) Endothermic. Water absorbs the heat necessary for evaporation from your skin, and your skin feels cooler.
    c)Endothermic. Ice absorbs the necessary heat from the environment to melt.
  2. The bond strengths of the products should be stronger than the bond strengths of the reactants. If the bond strengths of the products are higher, it would release a lot of energy, making the reaction very exothermic and hence a good explosion
  3. Heat is a form of energy. In contrast, temperature is a measurement that indicates the direction heat will flow.
    Heat always flows from an object at high temperature to an object at lower temperature. This means that if hot water is added to cold water, heat will flow from the hot liquid to the cold liquid, and the final temperature of the mixture will be between the original temperatures of the two individual solutions. Heat depends on the temperature and on how much material is present.
  4. a. Gasoline with an octane rating of 92 has the same knocking characteristics as a mixture composed of 92% isooctane and 8% heptane. In essence, this is a blend that is resistant to knocking.
    b. The octane rating does not give you any additional information about whether or not the fuel contains oxygenates. Other labels around the pump should reveal this information.

Week 3

Today we learnt about the impacts of air pollution and the composition of the air pollution. We have also discussed whether pedestrian or passenger will be more exposed to air pollution.


My First Post

Today is the first lesson of CM8001 (Impact of Chemistry on Society). I have learnt about the impacts of air pollution and how certain reactions can lead to adverse effects on the environment.

Do pedestrians inhale less pollution than passengers?


CM8001 Lecture (Week 3)

Today we learnt more about the chemistry of the composition of air and pollution, which includes nitrogen oxides, sulphur oxides, VOCs and particulate matter.

We also learnt how to create a post in this blog.

This is why this post is written. kthxbye