Q1. 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. 

Purify water by boiling, Use water purification tablet, Use small amount of household bleach.

Boiling kills many microorganisms that may make you sick, but requires time and will not remove chemical contamination. Boiling also requires time, fuel, and may release soot and CO to the environment.

Water purification tablet such as iodine tablet is easy and effective in twenty minutes, but it should not be used long-term. In addition, pregnant women and people with thyroid conditions should avoid purification with iodine. While iodine renders water bacteriologically safe, it doesn’t remove chemical contaminants. Many people dislike the taste of iodine-treated water.

Using a small amount of household bleach will kill some but not all microorganisms. Many people dislike the resulting taste.

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

The two most common desalination techniques are distillation and reverse osmosis. Both of these require large amount of energy to remove salts from seawater, and thus inherently are expensive. If a less expensive option is available, then the less expensive option is used.

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 NEA.

a. What is the likely major source of the lead in the drinking water?

The likely source of lead is from solder in the pipe joints or from lead pipes themselves.

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

Research activities should not contribute to lead in the drinking water, assuming that any lead compounds are disposed of using prescribed methods. Although many undergraduate chemistry experiments used to use lead, most now have been redesigned to avoid it and other toxic metal ions completely.

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

Fat-soluble is non-polar and water-soluble is polar compound. Fat-soluble contains long chain of non-polar hydrocarbons while water soluble compound contains polar chains.

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: Earth does not cool rapidly because the atmosphere retains most of the emitted heat energy, even though the amount of energy emitted is more than double the amount of heat received. 

Q2. Decide and explain whether the statement is correct or incorrect. 

Answer: The statement is incorrect. The winter experienced in the cartoon should raise their concern about global warming because the amount of snow is not normal as there is too much snow. This shows erratic climate change which should be a concern as a result of global warming.

Q3. 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?

Answer: Absorption of microwave radiation by water molecules 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)?

Answer: In the short run, air quality poses the most serious problem because it causes immediate harmful effects on human’s respiratory system.

In the long run, global warming poses the most serious problem because it leads to climate change and stratospheric ozone depletion which are irreversible, affecting the entire human population as well as ecosystem instead of a particular region.

Q1. From personal experience, state whether these processes are endothermic or exothermic. Give a reason for each.

a. A charcoal briquette burns.

Exothermic. Heat is being released when the charcoal briquette burns.

b. Water evaporates from your skin.

Endothermic. Water absorbs heat for evaporation.

c. Ice melts.

 Endothermic. Ice absorbs heat to melt.

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

The bond energies of the products have to be larger than the bond energies of the reactants to result in an exothermic reaction, which would then make for a good explosion.

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

Heat is a form of energy and it flows from a warmer body to a colder body. Temperature is a measurement that indicates the direction of heat flow. For example, when a cup of hot water is poured into a cup of cold water, the heat will flow from the hot water to the cold water and the resulting temperature is a mixture of both.

Q4. A premium gasoline available at most stations has an octane rating of 98. What does that tell you about:

a. knocking characteristics of this gasoline?

Gasoline with an octane rating of 98 has the same knocking characteristics as a mixture composed of 98% isooctane and 2% n-heptane and is more resistant to knocking than other blends sold at stations.

b. whether the fuel contains oxygenates?

No, it does not tell us whether the fuel contains oxygenates.