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.

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.

Answer:

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.