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Q1) How can your purify water when 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.

Answer:

One method of distillation is boiling the water (using solid fuel or starting a fire from wood) and collecting the condensed steam on a sheet. Another method involves the use of a small water purification device that can be purchased from stores. Both methods involve the use of equipment, especially in the second method. The first method may be easier to use as more of the items can be found from the surroundings (e.g. wood) but it is slower than the second method. The second method involves the use of special equipment that perhaps only experienced hikers would carry, although it may be faster to obtain purified water than the first method. None of these methods are similar to the ones used to purify municipal water supplies as the purification process at the treatment plants involve the adding of various chemicals in various stages and involves equipment ans substances which the average person would not have access to.

 

Q2) Explain why desalination techniques, despite proven effectiveness, are not used more widely to produce potable drinking water.

Answer:

Desalination techniques come at a relatively high cost and thus will not be used on as large a scale as cheaper methods as long as these cheap methods are available and able to meet demand for potable water. Also, the quantity of potable water produced from desalination is little. For example, Tampa Bay Water’s facility is the largest seawater desalination plant in North America but it can only produce 25 mgd of water at full capacity, which only satisfies about 10% of the region’s needs.

 

Q3) 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 the NEA.

A) What is the the likely major source of the lead in the drinking water?

Answer:

Likely sources include: the pipes (if plumbing is not done properly), soldering, and corrosion of the pipes in which the pipes are old and cracked.

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

Answer:

Yes, if improper disposal of chemicals is being carried out, with these chemicals being dumped into a place where it is able to leak into the drinking water.

 

Q4) Some vitamins are water-soluble, whereas others are fat-soluble. Would you expect either or both to be polar compounds? Explain.

Answer:

We would expect the water-soluble vitamins to be polar and the fat-soluble vitamins to be non-polar. This is because like dissolves like, and since water is a polar substance it can dissolve the water -soluble vitamins which are also polar. Since fat is a non-polar substance it should dissolve the fat-soluble vitamins which are also non-polar.

 

References:

  1. Water supply. (n.d.). Retrieved February 22, 2017, from http://www.tampabaywater.org/tampa-bay-seawater-desalination-plant.aspx

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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:

Even though the amount of energy emitted from the Earth’s surface is more than double the amount received from the Sun, the Earth does not cool rapidly because the Earth’s surface absorbs a large amount of energy from the atmosphere.

 

Q2) Decide and explain where the statement is correct or incorrect.

Answer:

The statement is incorrect for a number of reasons. First, the two people are assuming that just because their winter is colder than usual, global warming, which is a global phenomenon, must not be as severe as previously thought. They have confused weather, which refers to day-to-day changes, with climate, which refers to long-term patterns. In this case, the people assume the weather they are experiencing at the moment can be generalised to describe global climate patterns. Second, they do not realise that the heavy snowfall they are experiencing could in fact be a result of climate change brought about by global warming, as climate change results in more extreme weather.

 

Q3) One of the first radar devices developed during World War 2 used microwave radiation of a specific wave range that triggers the rotation of water molecules. Why was the design not successful?

Answer:

It was because the absorption of microwave radiation by H2O in the atmosphere interferes with the detection of intended objects.

 

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)?

Answers:

Short run: Though the burning of fossil fuels contributes to global warming and decreased air quality, air quality has a direct impact on our everyday lives and can affect human health over a much shorter time frame than processes such as global warming. It is thus more of a concern in the short run.

Long run: Though ozone depletion and global warming are caused by human activities, there are already many regulations targeted at reducing the amount of chlorine, which depletes ozone, in the air. However humans as a whole are still burning fossil fuels which generate CO2 which contributes to global warming. The effects of global warming, which includes climate change, are also visible through climate patterns which can only be observed over longer periods of time.

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Q1) From personal experience, state whether these processes are endothermic or exothermic. Give a reason for each: A) a charcoal briquette burns, B) water evaporates from your skin, C) ice melts.

Answers:

A) It is exothermic. Burning is combustion which is an exothermic reaction.

B) It is endothermic. In order to change from liquid to gaseous state, water takes in heat from the surroundings in order to evaporate.

C) It is endothermic. In order to change from the solid state to the liquid state, ice needs to take in heat from the surroundings.

 

Q2) Chemical explosions are very exothermic reactions. Describe the relative bond strengths in the reactants and products that would make for a good explosion.

Answers:

The bond energies in the reactants should be higher than the bond energies in the products. This results in an exothermic reaction as heat is released during the reaction.

For example: CH4 + 2O2 -> CO2 + 2H2O

Bond breaking:

4 (C-H) + 2 (O=O)

4(416) + 2(498) = 2660

Bond forming:

2 (C=O*) + 2 (2 H-O bonds)

2(803) + 4(467 )= 3474

3474 – 2660 = -814

 

Q3) How might you explain the difference between temperature and heat to a friend? Use some practical, everyday examples.

Answers:

Heat is form of energy which flows from a hotter body to a colder body. This can be seen when you hold a hot cup of coffee and your hand becomes warm. This is due to heat flowing from the hotter body (the cup) to a colder body (your hand). Temperature determines the direction of heat flow. In this case, since the cup has a higher temperature than your hand, the heat will flow from the hot cup to your hand.

 

Q4) A premium gasoline available at most stations has an octane rating of 98. What does this tell us about A) the knocking characteristics of this gasoline and B) whether the fuel contains oxygenates?

Answers:

A) The fuel has a knocking characteristic of 98% isooctane and 2% heptane

B) The fuel does not contain oxygenates as the octane rating of the fuel (98) is too low for the fuel to contain oxygenates.