Application Exercise 3

Qn1) The burning of charcoal briquettes is an exothermic process. This because I went camping once and lit a fire surrounded by some rocks and sand. But some dry grass caught fire and it amplified quickly before it could be extinguished. Thus, it does not need additional energy to amplify and a lot of heat is released in the process.

   b) The evaporation of water from your skin in an endothermic process. This because once I forgot a bucket of water outside in the sun, and after a while the amount of water decreased. The water molecules gains energy from the environment and can therefore evaporate.
   c) The melting of ice is an endothermic reaction as well. This because if you place ice cubes in a glass of water they will melt. The melting speed depends on how warm the surrounded water is. This because the ice cubes gain energy from the surrounding which make them melt.

Qn2) Exothermic reactions are chemical reactions with releases energy. In order for this, the total energy of the reactants must be higher than that of the final products, in other words, the energy absorbed for breaking of bonds in the reactants must be less than the energy produced for the forming of bonds for the products. As such, the bond strength of the reactants needs to be lower than that of the products. For a good explosion to happen, a high enthalpy is needed for the release of large amount of energy.  Hence, the greater the difference between the bond strength of the reactants and products, the better the explosion.

Qn3) Temperature is the measurement of a heat source whereas heat is the energy found in that source. Heat can be transferred from a source to another source whereas temperature cannot be transferred. For example, when boiling water, the heat energy causes the water to boil; i.e. steaming and bubbling water under heat, whereas the temperature shows that the water is boiling at 100°C.

Qn 4. a) Gasoline with an octane rating of 98 has a high resistance to cause engine knock. Engine knock occurs when the fuel mixture ignites too early. High octane Gasoline burns slower and at a higher efficiency, thus it is more resistant to knock.

         b) Oxygenates are added to motor vehicle fuels to make them burn more cleanly, thereby reducing toxic tailpipe pollution, particularly carbon monoxide. Oxygenates are favored not only for their vehicle emission benefits but also their blending properties in motor gasoline. Thus, with the gasoline at a high octane rating, it is probable that it contains oxygenates.

 

Application Exercise 4

1. Majority of the energy leaving the earth’s surface does not go directly out to space.  The emitted energy is absorbed by clouds and by the gases in the atmosphere again.  Some of it gets redistributed by convection. Energy is also absorbed by the greenhouse gases such as methane, nitrous oxide, ozone, carbon dioxide and water vapor.  These gases constantly emit the sun’s energy back into the atmosphere and keep the earth a habitable temperature. The energy that doesn’t make its way out is responsible for global warming, which results in Earth not cooling rapidly.
   
2. The statement suggests that the occurrence of winter is an indication of reduced impact of global warming. This statement is incorrect. There may be certain regions of the Earth at certain period of time experiencing winter, however, this does not mean that the Earth is getting colder or the average temperature of Earth is getting lower.  The occurrence of winter is just a change in season and has nothing to do with reduced impact of global warming.  It is noted that global warming is the increase of Earth’s average surface temperature due to effect of greenhouse gases. Greenhouse gases are the primary cause of global warming. The occurrence of winter does not change the fact that there is still high concentration of greenhouse gases in Earth. To reduce the impact of global warming, we should instead reduce the emission of greenhouse gases. This can be done by planting more trees and reduced combustion of fossil fuel.
3. Microwave radiation induces rotational energy in its surrounding molecules. If a radar send out a large amount of radiation of this wavelength the molecules in the air, water and other surrounding objects would gain so much energy that they would start to emit heat. This heat could increase the temperature in a lake with a few degrees, making it hard for certain species to survive in this new environment. The surrounding air would also increase in temperature which may not be very suitable with the very popular topic global warming.
4. In the short run, air quality is the most problematic. This is because the negative impacts of air quality is felt directly. Poor air quality severely affects the quality of life as the it causes direct respiratory problems, allergies and negatively affect the state of living. On the other hand, the impacts of ozone depletion and global warming is not felt directly hence, in the short run, air quality is the most serious problem.

In the long run, global warming is the most important issue. While air quality affects the quality of life, it does not threaten life itself. Global warming in contrast, affect the life around the earth. The resulting altered climate, rising sea levels, melting of polar ice caps etc sabotages the livelihood of animals. Arguably, if this continues, the livelihood of human beings may be threatened as well. This is observed where low lying islands are being submerged by the sea due to rising sea levels. While ozone depletion may result in threatening of humans livelihood, it is not as severe. This is because it is easier to reduce substances that harms ozone then to reduce greenhouse gases. For example, the effort to reduce CFCs in the atmosphere has seen great success while many countries still struggle to control their emissions, due to conflicting economic interests.

Application Exercise 5 (22 Feb)

1. While hiking, you can purify your water via boiling. The basic rule is to make sure you bring the water to a rolling boil for 1 minute at lower altitudes and 3 minutes at altitudes above 2000 meters. Boiling will eliminate bacteria, protozoa, and even viruses. The downside is you’ll use up your cooking fuel and will need to wait for the water to cool down. Another method is to use Chemical Purification via tablets. These tablets dissolve in your water to purify it while weighing almost nothing and are small enough to keep in any pouch for convenience. Traditionally hikers used iodine tablets, but iodine wasn’t able to eliminate Cryptosporidium and also left the water yellow and tasting funky. Today hikers prefer Chlorine Dioxide Tablets, which purify water with a highly active form of oxygen as they dissolve. The downside is needing to wait 30 minutes for the tablets to effectively neutralize Giardia and up to 4 hours when Cryptosporidium is a concern. Lastly, a filtration solution and device can be used. These filter out bacteria and protozoa via microscopic pores in the filter media usually 0.2 microns or smaller, but do not eliminate viruses. Overall, the cheapest would be boiling but it is time consuming and not as efficient as the more costly tablets or filtration system.

The method that is most similar to the methods used in purification of municipal water is filtration where large amounts of water can go through membrane filtration. The filtration of municipal water is far more complicated though, with many steps and types of membranes used to filter out different kinds of impurities like sediments, ions or dissolved substances. These stages may vary depending on what the water is going to be used for (e.g drinking/ lab usage) Comparing to this, the filtration during hiking would be considered very basic and on-the-go.

2. Desalination techniques are not used more widely because its plants and processes are expensive. Also, the process of desalination requires a lot of energy. The same amount of energy can be invested into producing other more important things. Other than that, the brine removed from the desalination process may pollute the surrounding environment and kill the wildlife and vegetation found there.

3. The likely major source of the lead in the drinking water is from the water pipes that may have contained some lead components.

No. Improper handling of aqueous chemical waste may cause the leaks to the drinking water but most labs don’t dump toxic compounds such as lead into the sinks but into a waste treatment system. Measures such as reminders for students to make sure no unwanted chemicals will leave the lab and contaminate the water has been used.
4. Water-soluble vitamin includes vitamins B and C. They are considered as polar compounds because they have predominance of polar groups (hydroxyl groups) than non-polar groups (hydrocarbon regions). In addition, according to general rule of thumb, “like dissolves like”. In other words, polar molecule will combine with other polar molecule to form solution. Therefore, water-soluble vitamin is considered as polar molecule, as it can dissolve in water, which is a polar molecule with non-zero net polarity. Fat-soluble vitamin includes vitamin A, D, E and K. They are considered as non-polar compounds because they have predominance of non-polar groups (hydrocarbon regions) than polar groups (hydroxyl groups). Following the same rule of “like  dissolves like”, non-polar molecule will combine with other non-polar molecule to form solution. Therefore, fat-soluble vitamin is considered as non-polar molecule, as it can dissolve in fat or lipid, which are non-polar molecules having large regions of non-polar hydrocarbon.

Application Exercise 6

1.  a) Air pollution from coal-fired power plants includes sulfur dioxide, nitrogen oxides, particulate matter, and heavy metals, leading to smog, acid rain, toxins in the environment. The main causes of poor visibility are SOx, NO x and hydrocarbons. Cities that have substantial amounts of power plants would roll out a huge amount of these gases, and in large volumes, will form smog. Smog causes the air to be more opaque and thus low visibility. A good example of this phenomenon is in China where this is a norm, even though authorities have attempted to quell the problem.

b) Since the natural pH of rain is 5.5, the rainfall of the park would have a pH of 4.5. [H+] = 10-5.5 x 10 = 10-4.5  

 

2a) Instead of using an electrical dryer, hanging of clothes out help save electricity. In turn, less electricity has to be generated from power plants and thus, releasing less SO2 into the environment

b) Cycling, biking and public transport help reduce the number of vehicles on the road. With less vehicles, less NO2 are produced from the engines and thus, reducing acid formation from nitric acid

c) Machines such as dishwasher and washing machine uses large amount of electrical power to work each time. Thus, it is very inefficient if they are used with small loads, wasting electricity. More electricity would have to be generated from the power plants and thus, releasing more SO2 into the environment, increasing the formation of acid rain from sulphuric acid.

d) Hot water heaters uses up a large amount of electrical power. Adding insulation to the pipes and the heater would ensure that there is less heat loss to the surroundings, keeping water warm for a longer period of time. As such, less electrical energy is needed to heat up water. This in turn reduces the amount of electricity generated from power plants, thus reducing SO2 released into the environment.

e) Buying locally produced food would discourage the importing of food from abroad. With reduced importing of food, less overseas travel is needed. As a result, less carbon dioxide will be emitted into the surrounding. Hence, acid rain formation from carbonic acid will be reduced.

3a) Examples of acids: Sulfuric acid, H2SO4, Hydrochloric acid, HCl, Nitric acid, HNO3, Phosphoric acid, H3PO4, and Hydrofluoric acid, HF.

Examples of bases: Potassium Hydroxide, KOH, Silver Hydroxide, AgOH, Sodium Hydroxide, NaOH, Ammonium Hydroxide, NH4OH, and Boron Hydroxide B(OH)3.

b) Something that can define an acid is that it easily loses a proton in aqueous solutions. Depending on how easy it is deprotonated depends on the strength of the acid. In contrast a base loses a OH–-group in aqueous solutions. 

An acid usually tastes sour, has a sticky texture and has a pH below pH7 (neutral pH). A base tastes bitter, has a slippery texture and has a pH greater than pH7.

4) Singapore has not had a problem of acid rain. The only probability of her experiencing acid rain is due to dry deposition of chemical particles from the yearly haze that originates from Indonesia. This is because Singapore’s factories do not produce as much harmful acids into the atmosphere as compared to other large countries such as Canada and Europe.                      (References: “Environment And Climate Change Canada – Air – Activities To Reduce Acid Rain”. Ec.gc.ca. N.p., 2017. Web. 17 Mar. 2017)

Application Exercise 7

1) The Styrofoam packing polymer is composed of foaming agents. When the acetone dissolves the polymer, the gas from the foaming agent evaporates. Now that the gas has evaporated, the polymer collapses on itself and becomes denser since all the gas has escaped.

2(a) Branched LDPE cannot be used in this application because it is not resistant to cuts. Since surgeons have to perform various cuts on a human body, the gloves that they wear must be cut-resistant.

(b) HDPE is more orderly packed as compared to LDPE. Hence, it would be more difficult to break the orderly bonds as compared to disorderly bonds.

3) When the piece of plastic is stretched, the strip narrows and “necks down.” The molecules become aligned parallel to each other and in the direction of the pull. This alteration of the three-dimensional structure is not reversible, and if the pulling continues, the plastic breaks.When the same pulling force is applied to a piece of paper, the paper tears rather than stretching to any significant extent. The cellulose molecules in paper are held far more rigidly in place, and are not free to become aligned.

4(a) Polymers used within the human body should have the following properties

High chemical stability. The polymer is inert and resistant to chemical reaction with lipids, proteins, fluids and other debris present in the body

Adequate thermal stability. The polymer is resistant to deformation or dissolution at high temperature, must way above the body temperature (37oC)

Adequate mechanical properties (sufficient hardness/ strength). The polymer should not break easily and be tolerant to impact imposed on or by the body.

Non-toxic. The polymer should not contain any chemical composition that can dissolve and cause acute or chronic health problems ultimately

4(b) Contact lenses are made from three type of materials. The hard lenses made from PMMA. The GP contact lenses made from fluorosilicone acrylate. The soft lenses made from gel-like plastic. Polymers for contact lense that has close contact with the body should have the following properties

High chemical stability. The contact lense is inert and resistant to chemical reaction with materials, such as lipids, proteins, fluids (present in the eyes) or debris (when exposed to environment).

Adequate mechanical properties (sufficient hardness/ strength). The polymer should not break easily and be tolerant to impact imposed on or by the body. However, it should be soft enough to not cause any cuts or injuries on the cornea.

Good Wettability. Contact lenses allow thick coverage of tear film and smooth recovery of tear layer after eye closure and good visual acuity

Good oxygen transmissibility. Contact lenses allow oxygen to reach eye by diffusion and to ensure more breathable and healthy cornea.

4(c) The hard lenses made from PMMA (polymethyl methacrylate) and the soft lenses made from gel-like plastic. The hard lenses allow better vision clarity but is not as comfortable to wear and may fall out more frequently. The soft lenses is more comfortable and has less tendency to be displaced but it can affect the vision clarity and cause some eye irritation.

 

 

Application Exercise 9 

1a. Its chemical formula is C₅H₉N_3.

1b.  

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1c.  The amine functional groups make the compound water-soluble as they are able to form hydrogen bonds with the water molecules.

 

2a. The chemical formula for this compound is C₁₆H₂₁N₃.

2b. Antihistamine also has three amine functional groups, as seen in histamine. However, the amine groups in antihistamine are less reactive than those in histamine as they are more hindered. Hence, when the antihistamines occupy receptor sites on cells normally occupied by histamines, there would be no reaction between receptor sites and histamines.

 

3. Physiological Response: Estrogen, Amphetamine

Inhibitors: Aspirin, (Keflex) Antibiotic, Penicillin, Morphine

 

4a. I think that supplement manufacturers requires complete data on the herbs composition, standardization, stability, microbial and chemical contaminant testing methods and tolerance limits, safety and efficacy along with ingredient characterization. With these justifications, the manufacturers need to register each herbal medicines or products with the authority and to receive approval document subsequently to prove it is safe and effective for consumption.

4b. Yes, I know some information about Singapore’s legislation. According to Singapore legislation, it is the manufacturers or retailer responsibility to ensure traditional medicinal materials do not contain any controlled substances. Moreover, the heavy metal contents of the traditional medicinal materials do not exceed the certain limits. The labels and packaging materials of the traditional medicinal materials do not stipulate any of the 19 diseases/ conditions such as blindness, cancer, cataract, drug addiction, deafness and diabetes.