Unit 9: Molecules and Drugs

This week, we learned about drugs.

We were also warned not to take drugs. Here are our answers for AE9.

Question 1

In allergy sufferers, histamine causes runny noses, red eyes, and other symptoms. Here is its structural formula

(insert diagram)

  • Give the chemical formula for this compound


  • Circle the amine functional groups in histamine




  • Which part(s) of the molecule make the compound water soluble?

Amine groups present in the molecule 

Question 2

Antihistamines are widely used drugs for treating symptoms of allergies caused by reactions to histamine compounds. This class of drugs competes with histamine, occupying receptor sites on cells normally occupied by histamines. Here is the structure for a particular antihistamine,

(insert diagram)

  • Give the chemical formula of this compound


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

Ethylamine and heterocyclic system,

Question 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 with class does each of these drugs fall?

  • Aspirin (physiological response)
  • (Keflex) Antibiotic (inhibit the growth of substances)
  • Amphetamine (physiological response)
  • Morphine (physiological response)
  • Estrogen (physiological response)
  • Penicillin (inhibit the growth of substances)

Question 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.

  • What do you think is the evidence for herbal supplement manufacturers that address these issues?

Herbal supplements are regulated by FDA (in the USA) but not as drugs or as foods. They fall under the category of dietary supplements. There is a comprehensive list of regulations on dietary supplements on the FDA website. This provides assurance that herbal supplements meet certain quality standards and that the FDA can intervene to remove dangerous products from the market.

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

In Singapore, herbal supplements are categorised as health supplements. Currently, health supplements can be imported and sold without a license from Health Science Authority (HSA). There are guidelines to be followed, but no legislation for herbal supplements.

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.


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


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.

Unit 5: Water for Life

This week, we talked about water in class.


Here are our answers for AE5.

Question 1

How can you purify your water 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.




Cost (cheapest to most expensive): boiling –> filtration –> chemicals

Effectiveness (most effective to least effective): chemicals = filtration –> boiling

Distillation and chlorination are done to purify municipal water supplies.

Question 2

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

There is high energy consumption during desalination to remove salt from seawater. This is very expensive and not cost-effective. There are cheaper alternatives such as finding sources of potable water (groundwater, lakes, etc.)

Question 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.

  • What is the likely major source of lead in the drinking water?
  • Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain.

The likely sources of lead are solder from lead pipe joints or lead pipes themselves.

No, the research activities carried out in the building do not account for the elevated lead levels found in the drinking water. Many experiments carried out in the building have been redesigned to exclude the use of lead and toxic chemicals. Also, the building is likely to have a waste disposal system that is separate from water sources.

Question 4

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

Polar compounds have bonds that are of high electronegativity difference. Non-polar compounds have bonds that are of lower electronegativity difference. Water-soluble vitamins are polar compounds while fat-soluble ones are non-polar. 

Polar compounds can form hydrogen bonds with water. Since water-soluble vitamins are polar compounds, they are able to dissolve in water.

Non-polar compounds cannot form hydrogen bonds with water. The weak interactions they form with water are not strong enough to break the intermolecular forces between fat-soluble compounds. Thus, they cannot dissolve in water.

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Unit 3: Global Climate Change


This week, we covered Unit 3: Global Climate Change. 140923233321-01-climate-change-impact-restricted-super-169

Here are our answers for AE 4.

Question 1

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/m^2. Why isn’t Earth cooling rapidly?

Although the energy leaving the Earth is greater than the energy absorbed by the Earth’s surface, the Earth does not cool rapidly as the atmosphere retains some of the energy emitted by the Earth’s surface.

Question 2img_4560Decide and explain whether the statement is correct or incorrect. Explain.

The statement is incorrect. The people in the cartoon are questioning why it is getting colder when everyone is concerned about global warming. They believe that the colder than usual winter is evidence to disprove global warming.  

However, global warming is actually an increasingly concerning phenomenon. Not only has it led to extreme temperatures, it has also led to rising sea levels, increasing occurrences of droughts and hurricanes. 

The main problem with this comic is that the people are confused between the terms “weather” and “climate”.

Weather is the day to day condition of the atmosphere. This includes temperature, rainfall and wind. Climate is the average weather conditions of a place, usually measured over one year.

Question 3

One of the first radar devices developed during World War II used microwave radiation of a specific wave range that triggers the rotation of water molecules. Why was the design not successful?

The radar device was designed to detect radiation reflected back onto the device. However, it did not work.

Microwave radiation has lower energy than infrared radiation. Water molecules can absorb microwave radiation and interfere with the detection of intended objects.

Question 4

Now that you have studies 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)?

The most serious problem in the short term is the air quality. It directly affects the air we breathe and can cause respiratory problems.

In the long term, we have to worry about global warming. Melting ice caps and rising sea levels can lead to the submergence of many low-lying coastal regions such as Singapore. Global warming is not an immediate concern as it takes time for ice caps to melt and temperatures to rise before the Earth becomes inhabitable.

Energy From Combustion

It’s week 5, and we got our group topic today: Energy From Combustion.

This week, we covered Unit 4: Energy from Combustion.


Here are our answers for AE 3.

Question 1

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

a. A charcoal briquette burns

It is exothermic because heat is released by the charcoal briquette. We are able to feel the heat from the fire.

b. Water evaporates from your skin

It is endothermic because heat is gained by the water.

c. Ice melts

It is endothermic because heat is gained by the water to be gas.

Question 2

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

The total bond strength of the product has to be stronger than that of the reactant such that more energy is released during the bond formation than is absorbed during the breaking of bond in reactants.

Question 3

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

Heat is a form of energy while temperature is a measure of heat. For example, when boiling water, heat is transferred to water to raise its temperature to its boiling point.

Also, heat is both a noun and a verb while temperature is only a noun.

Question 4

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

a) the knocking characteristics of this gasoline?

A gasoline’s octane rating is a measure of the gasoline’s resistance to causing knocking in a vehicle’s engine. The higher the rating, the more resistant it is to knocking in a vehicle’s engine and also the more branched the molecule.

An octane rating of 98 shows that there will be very little knocking.

b) whether the fuel contains oxegenates?

The octane rating tells us nothing about whether or not the fuel contains oxegenates.

250117’s Lesson

MBSIt is inevitable that there will be anthropogenic pollutions due to the high standards of living.

Knowing more about these pollutants may allow us to make informed choices on how to reduce them. 😊

My first post: Pollution


The most interesting question for today was the last question: Do pedestrian inhale less pollution as compared to passengers?

This question generated a variety of responses from people of different background, which was quite interesting.