1. Explain why Strontium 90 might be absorbed by your body, and why this would not be a good thing. Give an example of where this might have happened (we discussed several of these).
Strontium-90 is a radioactive isotope of strontium commonly found in nuclear fallout. It is chemically similar to the element calcium found in the body in bones, leading to it being absorbed as readily as calcium. While naturally stable forms of strontium can be absorbed by the body to no or even beneficial effects (research shows it being capable of increasing bone density and strength), strontium-90 can lead to bone cancer or leukemia. Historical testing of nuclear weapons by France in the 1960s released huge quantities of fallout into the atmosphere, leading to elevated rates of cancer among Polynesians living in the area of the tests.
2. Explain why Cesium might be released from a recent accident, and how it would impact your body, using the periodic table.
Caesium-134/137 was observed to be released into the air from the site of the Fukushima Daiichi Nuclear Power Plant in the aftermath of the 2011 Japan earthquake and tsunami. This led to soil contamination in the surrounding areas of farmland, which led to trace amounts of caesium-134/137 to be found in agricultural products across Japan. Caesium is chemically similar to potassium and rubidium because it is in the same column on the periodic table, and the body will absorb it as such. Once in, caesium will spread throughout the body and eventually cause death.
3. Why might soap disable a plants' ability to draw water up to its leaves?
Soap disrupts the ability of water molecules to cling to each other through cohesion, which is key to the phenomenon of capillary action, the method by which most plants use to draw water up to its leaves.
4. Explain how soap changes surface tension, and how this might be helpful in removing grease.
Similar to how it can impede capillary action, soap disrupts the hydrogen bonds between water molecules that allow water to maintain its surface tension. Soap contains micelles which are hydrophilic on the outside, and lipophilic on the inside. These cover grease and fat molecules, while the outer hydrophilic layer allows it to be dispersed and washed away by water.
5. Which pairs of nucleotides bond to each other in the DNA strand?
Adenine bonds with thymine, while cytosine bonds with guanine.
6. The inset on water mentioned several other physical qualities that could be important to life on this planet. Explain how specific heat and heat of vaporization enable life as we know it on our planet, and why Keck is looking for liquid water in the universe.
Water's high specific heat (second highest of any known substances, after ammonia) makes it highly resistant to changes in temperature and allows it to act as a global temperature buffer, for over 70% of the Earth's surface is covered by it. Water's high heat of vaporization allows it to effectively cool the planet by drawing off heat in the process of converting water molecules to a gas. Both of these processes help to moderate global climate within ranges suitable for life. Water is essential to life as we know it; the presence of liquid water on other planets may imply the existence of extraterrestrial life.
7. Locate the main "sinks" for the following: carbon, phosphorus, nitrogen, oxygen, sulfur
The largest carbon sinks are the oceans. The main sink for phosphorus is in water as deep ocean sediments. Nitrogen is primary located in the air at a 78% concentration. Oxygen is also located in the air, as most of the remaining 22%. Sulfur sinks in the Earth are mostly located underground as iron disulfide or calcium sulfate.
8. Lookup the following functional groups (wikipedia is useful here) and label each with it's charge: carbonate, nitrate, phosphate, sulphate, chloride, hydroxide, ammonium
Carbonate has a charge of -2. Nitrate has a charge of -1. Phosphate has a charge of -3. Sulphate has a charge of -2. Chloride has a charge of -1. Hydroxide has a charge of -1. Ammonium has a charge of +1.
9. Using your answers above, combine each functional group with one of these: hydrogen, calcium, chlorine, potassium, sodium
H2CO3: carbonic acid. HNO3: nitric acid. H3PO4: phosphoric acid. H2SO4: sulfuric acid. NaCl: sodium chloride. NaOH: sodium hydroxide. NH4Cl: ammonium chloride.
10. Which of your answers above are acids or bases?
Carbonic acid, nitric acid, phosphoric acid, and sulfuric acid are all acids. Sodium hydroxide is a base. Sodium chloride and ammonium chloride are salts.
11. You are now a third-world farmer (not the correct term, but the name of a simulation game) and need to ensure your crops have the proper major nutrients. What are these three nutrients, how do we refer to them in fertilizer, and what form do they often take in this fertilizer?
The three most common nutrients in fertilizer are nitrogen, phosphorus, and potassium. They appear in fertilizer as nitrogen, phosphorus pentoxide, and potassium oxide, represented by an NPK rating that describes the mix of these three compounds.
12. Water is "amphoteric". What does this mean, and include some form of structure in your answer.
Water is amphoteric; therefore it can react as an acid as well as a base. When water is mixed with an acid like hydrogen chloride, it acts a base and neutralizes it (H2O + HCl → H3O+ + Cl-). When it is mixed with a base like ammonia, it acts as an acid (H2O + NH3 → NH4+ + OH-).
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