AE9: Molecules & Drugs


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1. In allergy sufferer, histamine causes runny noses, red eyes, and other symptoms.

a. Give the chemical formula for this compound.

b. Circle the amine functional groups in histamine.

c. Which part (or parts) of the molecule make the compound water-soluble?

a. C5H9N2
c. N atoms have negative dipole moments which can form hydrogen bonds with H+ of H20 molecules


2. Antihistamines are widely used drugs for treating symptoms of allergies caused by reactions to histamine compounds. This class of drug competes with histamine, occupying receptor sites on cells normally occupied by histamine.

a. Give the chemical formula for this compound.

b. What similarities do you see between this structure and that of histamine (shown in the previous question 1) that would allow the antihistamine to compete with histamine?

a. C16H21N3
b. Two-carbon chain with an N at the end and a three atom sequence N-C-N.


3. Consider this statement. ‘Drugs can be broadly classed into two groups: those that produce a physiological response in the body and those that inhibit the growth of substances that cause infections.” Into which class does each of these drugs fall?


Physiological response





Inhibit growth of substances

-(Keflex) antibiotic





4. Herbal or alternative medicines are not regulated in the same way as prescription or OTC medicines. In particular, the issues of concern are identification and quantification of the active ingredient, quality control in manufacture, and side effects when the herbal remedy is used in conjunction with another alternative or prescription medicine.

a. What do you think is the evidence from herbal supplement manufacturers that address these issues?

b. Do you know anything about Singapore’s legislation on the topic?

a. Products like herbs are sometimes tainted with germs, pesticides, or toxic heavy metals. Other supplements do not contain what’s listed on the label. This is because some herbal manufacturers mix or substitute products with cheaper alternatives. As such, the purity of these medicines become obscured as testing becomes less reliable.
b. We know that there is currently not much strict enforcement of legislation but regardless dealers have the responsibility to ensure that their health supplements do abide with safety and quality standards.

AE 7: The World of Polymers and Plastics


1. When Styrofoam packing peanuts are immersed in acetone, 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.

Answer: Styrofoam is composed of 98% air. When polystyrene dissolves in acetone, the air in the foam is released, thus compacting the Styrofoam into a solid which is much 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.

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


a. Branched LDPE are softer and more flexible but have lower tensile strength, thus, during a surgery, it may break easily exposing surgeons to viruses or bacteria present.

b. The polymer chains in HDPE, on the other hand, are more linear. They pack closer together, resulting in greater intermolecular forces and a more “crystalline” structure. HDPE has greater tensile strength than LDPE.

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.

Answer: No it does not happen to paper. For plastic bags, the molecules are packed together with high degree of branching, thus creating a less strong intermolecular forces which results in lower tensile strength and increased ductility. This happens in the opposite manner for paper whereby paper has a low ductility characteristic.

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.

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.

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?


a. The properties are (1) stable over time of intended use, (2) non-toxic, (3) inert and (4) light. Other factors to consider are low cost, lack of solubility in body fluids, and the ease of implantation.

b. Polymethyl methacrylate (PMMA), one of the earliest polymers used for rigid gas permeable lenses. Silicone-acrylate materials now are more commonly used under trade names such as Kolfocon. Desirable properties include being nontoxic, permeable to oxygen, comfortable to wear, and inexpensive. Also desirable is the ability to conform to the shape of the eye and to be easily cleaned.

c. Hard contact lenses are typically made of PMMA, a rigid non-gas permeable plastic. The soft contact lenses that replaced them 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: Neutralising the Threat of Acid Rain


1. Mammoth Cave National Park in Kentucky is in close proximity to the coal-fired electric utility plants in 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.
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.


a) Coal-fire plants produce sulphur dioxide creating sulfate particles which is responsible for the poor visibility.

b) Normal rain pH is about 5-6 pH. If the average rainfall in Mammoth Cave National Park is 10 times more acidic, this means that the pH of the rainfall is 4-5 pH.

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.
b) Walk, bike, or take public transportation to work.
c) Avoid running dishwashers and washing machines with small loads.
d) Add additional insulation on hot water heaters and pipes.
e) Buy locally grown produce and locally produced food.


a) Water evaporates from the clothes which in turn produces water vapour. H2O combines with SOx and NOx in the air to produce H2SO4 and HNO3 (Acid rain).

b) Public transportation produces NOx from the exhaust which dissolves with H2O in the air to form HNO3 which in turn contribute to the possibility of acid rain.

c) The amount of electricity needed to run dishwashers and washing machines does not change with the amount of load. As such, more fuel is required to run the machines and in turn produces compounds which contribute to the formation of acid rain.

d) With additional insulation on hot water heaters and pipes, this increases the efficiency of the heat systems as there will be lesser heat loss to the surroundings. As such, lesser fuel is required to compensate for the negligible heat loss.

e) Buying local food, this amounts to lesser import by plane or ships. This results in less fuel burnt to run the planes and ships and thus, reducing the chance of acid rain formation.

3. a). Give names and chemical formulas for five acids and five bases.
     b). Name three observable properties generally associated with acids and bases.



Hydrochloric Acid (HCl) Ammonia (NH3)
Sulphuric Acid (H2SO4) Sodium Hydroxide (NaOH)
Nitric Acid (HNO3) Magnesium Hydroxide (Mg(OH)2)
Phosphorus Acid (H2PO4) Ammonium Hydroxide (NH4OH)
Sulphurous Acid (H2SO3)

Calcium Hydroxide (Ca(OH)2)

1. Acids turn blue litmus paper red.
2. Bases turn red litmus paper blue.
3. When acid reacts with an active metal, effervescence is observed and gas evolved will extinguish a lighted splint with a ‘pop’ sound.
4. Bases feel slippery and soapy.

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?


In the course of pursuit for industrialization to reach a level of development, many Asian nations emphasized on economic development, coupled with the high rate of population growth stemming from an already large population base, guarantees that SO2 and NOx emissions will increase significantly. This is because technology is emerging at a rapid rate, cutting the need for manpower and in turn, increasing the usage of machines.

As atmospheric contaminant are able to be transported over a long distance before it is being deposited, atmospheric pollution and acidification in Asia is a cause of concern to the Singapore Environment.

AE 5: Water for Life

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1. How can you purify when you are hiking? Name two or three possibilities. Compare these methods in terms of cost and effectiveness. Are any of these methods similar to those used to purify municipal water supplies? Explain.

The possibilities are chlorine tablets, heating and filter paper. These are inter-related to each other and could purify water during hiking. The methods mentioned are cheap but time inefficient as it takes a very long time to purify a certain amount of water using the methods above. 

The methods are similar to a certain extent as those used to purify municipal water supplies also use filtration and chlorination.

2. Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce portable drinking water.

Desalination has been proven to be an effective , workable and trustworthy method for producing portable drinking water. However, there are disadvantages to this method.

Firstly, it comes at an opportunity cost of land space. This could impinge upon the natural habitats of wildlife and thereby disrupt the ecosystem. Farming and agricultural practices would be affected as these are subsistence require large land area in order to be produced. 

Secondly, it is very cost ineffective. Besides the equipment itself being expensive to assemble, a large amount of energy has to be input into the system across a long period of time. Yet, the yield of the portable drinking water from desalination is very low and thereby cannot offset the capital invested in these plants and hence it is not monetarily worthwhile in the long run.

Lastly, desalination entails environmental repercussions. Chemicals such as Hydrogen peroxide and chlorine are added as part of the treatment process, only to be disposed of thoughtlessly afterwards into water bodies, causing an accumulation of harmful substances that could very well enter our food chain in time.

3. Water quality in a chemical engineering building on campus was continuously monitored because testing indicated water from drinking fountains in the building had dissolved lead levels above those established by NEA. 

a. What is the likely major source of the lead in the drinking water? 

The most likely major source of the lead in the drinking water is probably from the corrosion from the pipelines. 

b. Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain. 

No. This is because the pipes connecting and chemistry lab and those connecting to the drinking water source are not interconnected. Especially when it is a chemical engineering plant where there is a proper disposal of chemicals from any research or experiment.

4. Some vitamins are water-soluble, whereas others are fat-soluble. Would you expect either or both to be polar compounds? Explain. 

Water-soluble vitamins are polar whereas fat-soluble vitamins are non-polar.

Water-soluble vitamins are highly polar due to the presence of many hydroxyl (OH-) groups which can form hydrogen bonds with water.

Fat-soluble vitamins are non-polar due to the absence of polar groups and the long hydrocarbon chain (C-H) makes it insoluble in water as it is unable to form hydrogen bonds.

AE 4: Global Climate Change

Q1. Understanding Earth’s energy balance is essential to understanding the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square meter (W/m²), but the energy leaving Earth’s surface averages 390 W/m². Why isn’t Earth cooling rapidly?
Answer: The Earth isn’t cooling rapidly even though the amount of energy leaving the Earth’s surface is twice the amount of energy striking the Earth’s surface because of the greenhouses gases in the atmosphere trapping the heat. The reason for the huge difference is also due to anthropogenic sources of carbon emission such as fossil fuel usage/slash & burn and industrial processes, therefore, adding to the increase of energy leaving the Earth’s surface.

Q2. Decide and explain where the statement is correct or incorrect. Explain.
Answer: The statement is incorrect. If there are extreme weather conditions, it means that global warming has worsened. Winter in certain parts of the globe doesn’t indicate that global warming is not detrimental to Earth and that other parts of the globe is not affected by global warming.

Q3. One of the first radar devices developed during World War II used microwave radiation of a specific cell age range that triggers the rotation of water molecules. Why was the design not successful?
Answer: The design was not successful because of the wrong use of radiation. The frequency of microwave is too low and hence, is not high enough to penetrate to the chemical bonds to trigger the rotation of water molecules.

Q4. Now that you have studied air quality (unit 1), stratospheric ozone depletion (unit 2), and global warming (unit 3), which do you believe poses the most serious problem for you in the short run (pick one and explain)? In the long run, (pick one and explain why)?
Answer: In the short run, global warming poses the most serious problem because of the emission of greenhouse gases and extreme temperature. This directly causes factors (e.g increase of sea level, temperature of Earth) that poses as more imminent danger to living things such as health issues or environmental problems. In the long run, ozone depletion causes the most serious problem. This is because of the hole created in the ozone layer that protects us from the ultraviolet rays of the sun and the other dangers (e.g injury to marine organisms and plants) that arises from the sun’s ultraviolet onto the Earth.

So many layers in the skies

Image result for different layers of ozone

Today I learned that there are actually so many different types of ozone layers and that each of them has their unique properties and functions. It took me by surprise to realize that the Ozone itself can be a pollutant if they are on ground level. I thought it had a sole purpose of protecting us.

AE 3: Energy from Combustion

1. From personal experience, state whether these processes are endothermic or exothermic. Give a reason for each.

A) A charcoal briquette burns.
Answer: Exothermic. Energy released when charcoal burns.

B) Water evaporates from your skin.
Answer: Endothermic. Water takes in heat energy and changes from liquid to gaseous state.

C) Ice melts.
Answer: Endothermic. Ice takes in energy and changes from solid to liquid state.

2. Chemical explosions are very exothermic reactions. Describe the relative bond strengths in the reactants and products that would make for a good explosion.


Energy released when breaking bonds > Energy taken in when forming bonds.

There has to be a huge difference of the bond strength of products and reactants, whereby bond strength of products > Bond strength of reactants.

3. How might you explain the difference between temperature and heat to a friend? Use some practical, everyday examples?

Answer: Heat will flow from higher to lower temperature while temperature indicates the direction. An example is when a dry towel placed on wet area, heat flows from towel to wet area, while temperature is the temperature of water.

4. A premium gasoline available at most stations has an octane rating of 98. What does that tell you about:

A) The knocking characteristics of this gasoline?
Answer: Octane rating is the measure of the ability of gasoline to burn smoothly without knockng. The knocking characteristics is 98% isooctane and 2% heptane.

B) Whether the fuel contains oxygenates
Answer: Higher octane ratings means that fuel contains more oxygenates.

Ozone Screen or Ozone Layer?

The term “ozone layer” is often referred by people as a covering of ozone surrounding Earth but the term does not have a functional meaning to it as people may not necessarily know it actually serves the purpose of protecting the earth from harmful radiation. But apart from the function, what is the mechanism behind it’s protective “screening” ability?

Ozone can absorb highly energetic and harmful UV-B and UV-C light and hence break into oxygen atom and oxygen molecule, effectively absorbing the harmful radiation. The oxygen atom reacts with oxygen molecule to form ozone again making it ready to absorb UV radiation again, hence the cycle repeats it self.


The Oh-zone Layer

The ozone layer is depleting faster that it is replacing. Actions need to be taken in order for a more environmentally friendly world to live in. Meanwhile, manufacturing of new products to reduce ozone depletion are in place hopefully for a better future.ways-to-bring-down-ozone-layer-depletion

Protecting the Ozone Layer

The ozone layer is a deep layer in the stratosphere that has large amounts of ozone in it. The layer shields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun.

Ozone is a special form of oxygen, made up of three oxygen atoms rather than the usual two oxygen atoms. It usually forms when some type of radiation or electrical discharge separates the two atoms in an oxygen molecule (O2), which can then individually recombine with other oxygen molecules to form ozone (O3).