Wednesday, May 18, 2011

Exam Review Question #6

List the three main types of intermolecular forces and describe how each are formed Which intermolecular forces are the strongest and why?

1) Hydrogen bonds- strongest

-these bonds are polar molecules that form when a bond is made between H and F,N, or O -the large electronegativity difference in these bonds creates stronger dipoles

2) Dipole interactions- between polar molecules

-positive pole on one molecule is attracted to the negative pole of another -similar to ionic bonds but much weaker

3) London Dispersion forces- between non-polar molecules (weakest of all forces)

-step 1: Two molecules get close to each other

-step 2: The electrons in one molecule momentarily shift to form a dipole

-step 3: The momentary dipole in one molecule induces a dipole in another and they form an interaction

Thursday, April 7, 2011

Nuclear Chemistry: The Chernobyl Disaster

On April 26, 1986 at a nuclear power plant outside of Pripyat, Ukraine, several detonations occurred inside of the nuclear reactor, causing the 12,000 ton cover of the reactor to shoot up into the air. Radioactive vapor spewed into the air, blasting uranium and graphite hundreds of meters around the plant. Then a huge stream of fire and radioactive particles shot 1,000 meters into the sky (1). Many have claimed that this catastrophe was the result of human error and flaws in the design of the reactor including the use of graphite in construction and the lack of a containment structure around the reactor. This human error was most likely occurred when the operators of the plant began to perform unauthorized experiments in which they intentionally bypassed the reactors safety systems in an attempt to learn more about the plants operation. This caused one of the four reactors to quickly overheat and its water coolant radically increased in radioactivity, often referred to as "flashing" into steam. The hydrogen that formed from the steam reacted with the graphite in the moderator causing two major explosions and a fire, sending the core into a partial meltdown (2).

These nuclear reactors obviously aren't supposed to malfunction like this. Nuclear energy is very similar to other more conventional energy sources. Both use the heat generated from either burning the fuel in conventional methods or, in the case of nuclear energy, the heat generated from the fission of atoms in a chain reaction to create steam which spins a turbine to create electricity(3). In the nuclear reaction, fuel rods are made of uranium which when split creates a massive amount of energy. This makes nuclear energy advantageous because there isn't a need for a lot of fuel. For example, nuclear energy creation requires 28 tons of resources a year as opposed to a coal power station which would require 2,000 tons of coal per week. Producing nuclear energy, however, produces very dangerous and harmful waste, which if released into nature, like in the case of the Chernobyl incident, could result in serious harm (4).

After the explosion of the Chernobyl nuclear reactor, there was still a need to cover the source of the radiation which was rapidly being released into the atmosphere. Teams of helicopters had to fly over the source of the radiation and pour tons of sand and boric acid which neutralizes radiation. The workers sent on this mission were exposed to high amounts of radiation and many died because of it. Not only were the workers exposed to radiation, however, all of Pripyat was forced to evacuate to avoid the radioactive dust spewing from the reactor. 27 children reportedly died soon after evacuation due to severe radiation burns and other mutations. The radiation affected a widespread area, not only affecting the citizens of Pripyat. This radioactive dust in the air spread across Europe and was brought down by the rain, surprising other European countries who had not received word of the incident.

Although it has been 25 years, the destroyed reactor still remains encased in cement due to the massive amounts of radioactive material still trapped underneath. The area around the incident has still been heavily affected as well, with very few resettlement attempts made in the surrounding areas. The government of Belarus is beginning to make plans for resettlement but these contaminated areas pose a great threat to the inhabitants of the area (5).

In the midst of the Japan nuclear crisis, many are comparing the Fukushima and Chernobyl disasters. It is true that in Japan, radiation levels are approaching those seen during the Chernobyl incident. The main difference between these two incidents is that at Chernobyl a huge fire released large amounts of many radioactive materials, including fuel particles, in smoke. At Fukushimaonly the volatile elements, such as iodine and caesium, are bubbling off the damaged fuel. This crisis in Japan has the potential to be dangerous if the amount of radiation released begins to increase overtime. If so, some worry that the west coast of the United States is at danger(6).

Works Cited

Pictures Cited in Order They Appeared


Friday, November 12, 2010

Chemistry Exam Review Question

27)How many significant figures do each of the following have?
a)50.01cm- 4 significant figures
b).00120cm- 3 significant figures
c)82,400cm- 3 significant figures
d)33 students- This has unlimited significant figures because the number of students can be counted exactly and is not measured
e)100.001cm- 6 significant figures
f)the product of a times b- 50.01cm(.00120cm)= 0.0600cm^2-3 significant figures
g)the sum of a and c- 50.01cm + 82,400cm= 82,450cm- 4 significant figures

Thursday, October 7, 2010

J.J. Thomson's Cathode Ray Experiment

Before 1897, the atom was considered the smallest unit of matter and was indivisible. In 1897, however, the English scientist J.J. Thomson changed the ideas of matter drastically. With his cathode ray tube experiment, Thomson discovered the electron, particle more than 1,000 times smaller than the lightest known particle at the time, the hydrogen atom. Thomson proved that the atom was not indivisible and began study of matter at the sub-atomic level.

To learn more about Thomson's experiment, click on this link- J.J. Thomson's Cathode Ray Experiment

Monday, September 13, 2010

Finding the physical and chemical properties of a skittle

I chose a skittle as my household object because almost everyone, including me, likes skittles, and they are a very common thing to find in someone's pantry. I also chose a skittle because I learned that sugar burns, and I wondered how a skittle, which is almost completely made out of sugar, would burn.

Physical Properties
1. A skittle has a mass of about 1.134g
2. At room temperature, a skittle is a solid
3. The color of all of the skittles I used for my experiments was yellow
4. Has a smooth surface
5. A hard shell but easily crush able

Chemical Properties
1. A skittle does not react with water, however it does slowly dissolve.
2. When put in vinegar, the skittle did not react, and only dissolved slightly faster than the skittle that was put in the water.
3. A skittle does not catch fire, but it does burn. The skittle melts and bubbles when being burned.

4. When place in soda the skittle bubbles a lot, showing evidence of a chemical reaction. The skittle dissolves faster in the soda than in the water or vinegar, and a waxy lining forms at the top of the soda

5. When the skittle was heated on a pan, it began to melt, bubble, evaporate, change color, and burn all at once. Three of these things show that a chemical reaction has occurred. The final result of all of these processes is a black, shriveled skin.