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Application Exercise 5 (22 Feb)

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  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.

  1. 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: Session 4, Global Climate Change

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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.

Answers for Application Exercise Session 3: Energy from Combustion

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Qn 1. a) 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.