Wednesday, May 18, 2011

Final Exam Review

26) Most of the time, gases behave like ideal gases and the equation PV=nRT can be used for prediction. However, molecules that are polar(hydrogen especially) and/or are large and take up more space tend to deviate the most from the ideal behavior, making it no longer possible to use the above equation for prediction. The gases that do have volume that will resist compression and will form more dense states(i.e. solids and liquids) and gases that have intermolecular attractions that allow them to form liquid and solids are the ones that deviate. Another condition that makes gases act the least like ideal gases is high temperature and low pressure.

Heres a funny video that may help you remember the gas laws and concepts:

31) A)Which non-metals, apart from hydrogen, are most often involved in hydrogen bonding? Why these and not others? 

B) Ethanol and dimethyl ether have the same molecular formula C2H6O. Ethanol boils at 78.4°C whereas dimethyl ether boils at -23.7°C. Using their structures (pictured below), explain why the boiling point of the ether is so much lower than the boiling point of the ethanol.

ANSWER:
A) They are Oxygen, Nitrogen, and Flourine. The large difference in electro-negativity in these bonds create stronger dipoles. 
B) In Ethanol, there is a hydrogen bond between H and O. A hydrogen bond is much stronger than the other Van der Waals forces. When melting and boiling, one is acutally breaking the bonds. So, it is much harder to break the hydrogen bonds due to the stronger force and therefore, the boiling temperature must be higher. 

Monday, March 28, 2011

The Chernobyl Disaster

          In April of 1986, a terrible disaster occurred in the Chernobyl power plant in Ukraine. The accident destroyed the Chernobyl 4 reactor, which was a Soviet reactor known as a RBMK reactor, a ""reactor cooled by water and moderated by graphite". In order to understand this whole situation more clearly, one must first understand how a nuclear reactor functions. 
          The RBMK reactor is just like all other reactors in that it uses nuclear fission to split nuclei, creating energy. In order to do this, there must be a bombarding particle, for example a neutron, and a target particle, such as uranium. The bombarding particle splits the target particle's nucleus into two, almost equal parts, and the nuclear fission releases part of the energy of the nucleus. Some of this energy comes out in the form of radiation, but most of it is heat.
          Another important factor in this process is the moderator. When one tries to split the nuclei of many pieces of uranium, the neutrons move very fast, making it hard for the bombarding particle to even hit the uranium. The moderator is used in nuclear power stations to slow down the neutrons as they pass through it, making it easier to bombard many blocks of uranium at one time. Uranium is used in many nuclear power stations in the United States and Canada, but it was not used in the RBMK reactors at Chernobyl. The RBMK reactors use a pure form of solid graphite.
           A reactor is made up of three main parts: the reactor vessel, the core, and the control rods. Each has its own function, making up the nuclear reactor. The reactor vessel holds all of the reactor parts. The core is a huge container that is filled with the target material, and in the case of the RBMK reactors, graphite blocks. And, the control rods are long metal rods that contain that, in RBMK reactors, contain. Their function is to help control the reaction by absorbing free neutrons. There is a device right outside the nuclear reactor that inserts and withdraws the rods to slow down or speed up the reaction.
          During a reaction, the uranium or graphite fuel becomes hot. Water is then pumped through the core in the vessel and it removes the heat from the fuel. Due to this gained heat, the water then boils into steam. The steam then turns two turbines which spin electrical generators to produce electricity. The water is cooled and the process is done again.

But, during the Chernobyl accident, things were not done as they should have been. Engineers on the night shift at Chernobyl’s number 4 reactor began to experiment to see if the cooling pump system could still work using the power generated if the auxiliary power failed. The control rods were lowered in order to reduce the output to about 20% of the normal output required for the test. But, too many rods were lowered and output dropped too quickly, creating an almost complete shutdown.                                                                              



The engineers worried about instability so they decided to raise the rods to increase output. But, during this time, the automatic shut down was turned off to allow the reactor to continue in such low power conditions. The engineers continued to raise the rods and the output increased to about 12%. But, then all of a sudden the power levels sky-rocketed to dangerous levels. 



The reactor began to overheat and the water coolant started to turn to steam. It is believed that at this point, all but 6 rods had been removed, and the safe operating minimum is only 30. The emergency shut-off was pushed, sending the control rods back down into the reactor. But, this was a mistake because they were inserted from the top, which displaced the coolant and concentrated all activity to the core. 

The power levels surged to about 100 times the normal amount, causing the fuel channels to rupture. Two explosions occurred, causing the reactor's top to be blown off and the contents of the reactor to erupt upwards. As air was sucked into the broken reactor, flammable carbon monoxide gas cause a fire in the reactor that burned for a total of nine days. Because the reactor was not in a reinforced concrete shell, which is a standard safety procedure in most countries, the building suffered severe damage and large amounts of radioactive debris escaped into the atmosphere. 
The effects of the Chernobyl accident were devastating. Here is an image of all the areas affected:
The disaster released at least 100 times the amount of radiation of the bombs dropped on Hiroshima and Nagasaki. Two workers died of the explosion itself, with another 28 dying of Acute Radiation Syndrome (ARS) within a few weeks of the accident. The two main sources of radiation delivered to the people were iodine-131 and cesium-137. The total number of deaths due to the accident and radiation cannot be determined fully but there are many anticipated deaths due to the accident. The radiation has caused many cancers in its victims, especially thyroid cancer. About 4,000 cases of the cancer has been seen in victims related to the incident so far. The Greenpeace campaign group anticipates a total of 93,000 more cancer related deaths, making the death toll of the accident around 200,000. 


Here is how many people were affected by the disaster:

In order to prevent more exposure, many people were evacuated from surrounding towns but complete prevention was not successful. Fire-fighters were immediately rushed to the scene to put out the fire from the explosion and all weren't put out until 9 days later. Even after the fires were extinguished, radioactive particles were still escaping the reactor. In order to eliminate this, the Soviets devised a plan to pour concrete and place steel to form a shell around the reactor so that no more radiation would escape. They named it the Sarcophagus. 

The situation in Japan is similar to that of Chernobyl but not completely. Here is a video that explains why:


In conclusion, the Chernobyl accident is somewhat similar to the situation in Japan but graphite was not used in Japan. Chernobyl is a very significant disaster in world history and much was learned from the flawed structure and mistakes of the engineers. 


Works Cited:


"Backgrounder on Chernobyl Nuclear Power Plant Accident." United States Nuclear Regulatory Commission .

          NRC, 30 Apr. 2009. Web. 28 Mar. 2011.<http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/chernobyl-bg.html>.


Beegle, Bill, Peter Bleickhart, and Steven Quirk. "Chernobyl: A Nuclear Disaster." Oracle Think Quest. N.p., n.d.
         
          Web. 28 Mar. 2011. <http://library.thinkquest.org/3426/>.


"Chernobyl Accident." World Nuclear Association. N.p., Mar. 2011. Web. 28 Mar. 2011.


          <http://www.world-nuclear.org/info/chernobyl/inf07.html>.


"The Chernobyl Disaster." BBC News. N.p., n.d. Web. 28 Mar. 2011.


          <http://news.bbc.co.uk/2/shared/spl/hi/guides/456900/456957/html/nn1page1.stm>.


International Chernobyl Radiological Portal of the ICRIN Project. ICRIN Project, Web. 28 Mar. 2011.

          <http://chernobyl.info/Default.aspx?tabid=294>.

Saturday, January 29, 2011

Creative Chemistry

3) Everyday objects that we see can really be VESPR structures! You will be surprised!

  • Linear: dumbbell














  • Bent: Corner Couch












  • Trigonal Pyramidal: Earrings












  • Trigonal Planar: Pizza












  • Tetrahedral: Tripod


















4) Just in case you crave chemistry, here's a list of some edible covalent compounds that will most likely satisfy your appetite!
  1. Water
    • dihydrogen monoxide
    • Molecular Formula: H2O
    • Empirical Formula: H2O
    • Water is used for hydration and should be consumed every day! 
  2. Dextrose
    • hexacarbon dodecahydrogen hexoxide 
    • Molecular Formula: C6H12O6
    • Empirical Formula: CH2O
    • Pixie sticks and Smarties candies
  3. Ethanol
    • dicarbon hexahydride monoxide
    • Molecular Formula: C2H5OH
    • Empirical Formula:  C2H6O
    • Known as ethyl alcohol and is commonly used in most alcoholic beverages
  4. Carbon Dioxide
    • carbon dioxide
    • Molecular Formula:CO2
    • Empirical Formula: CO2
    • Commonly found in carbonated drinks, i.e. Dr. Pepper, Sprite, Coke, etc. 
  5. Sulfer Dioxide
    • sulfur dioxide
    • Molecular formula: SO2
    • Empirical formula: SO2
    • Commonly used as a preservative for many dried fruits

Saturday, December 11, 2010

Chemistry is Everywhere

When searching through our pantires and the aisles of the supermarket, we came across many different compounds further proving that.... CHEMISTRY IS EVERYWHERE!

Velveeta Cheese
1. calcium phosphate



Velveeta Cheese
2. sodium phosphate



Hormel Pepperoni
3. sodium nitrate



Safeway Disinfecting Wipes
4. ammonium chloride



Liquid Plumber Power Gel
5. sodium hypochlorite



Liquid Plumber Power Gel
6. sodium hydroxide



Fancy Feast Cat Food
7. potassium chloride



Fancy Feast Cat Food
8. zinc sulfate



Fancy Feast Cat Food
9. copper sulfate



Fancy Feast Cat Food
10. potassium iodide



Fancy Feast Cat Food
11. magnesium sulfate



Fancy Feast Cat Food
12. salt
 



Fancy Feast Cat Food
13. calcium carbonate



Fancy Feast Cat Food
14. iron (II) oxide



Fancy Feast Cat Food
15. cobalt (II) carbonate



Medical Scrub
16. ammonium sulfate



Herb Seasonsed Restaurant Style Croutons
17. calcium sulfate



Herb Seasonsed Restaurant Style Croutons
18. sodium acetate



Centrum Kids
19. magnesium oxide



Centrum Kids
20. manganese (II) sulfate
 

Tuesday, November 9, 2010

Trimester 1 Exam Review:

Question #19:
Give three distinct examples of quantum number combinations that cannot occur, and explain why they are impossible. Each example should illustrate a separate violation.


Example A)
(0,0,3,-1/2) - This combination cannot exist because the n #(the energy level) cannot be 0. 


Example B)
(3,3,1,1/2) -  This combination doesn't exist because it has the n and the l numbers the same.This is not possible.


Example C)
(1,2,1,1/2) -  This combination doesn't work because of the n and l numbers. The second number (l=2) represents a d orbital, but level (n=1) does not have a d orbital, making these quantum numbers impossible. 

Saturday, October 2, 2010

The Discovery of a Neutron

               Today, we take for granted our knowledge of the atom. But, this knowledge is very important to our world and if it wasn't for many hardworking scientists, we wouldn't have it. In this post I will tell you about the discovery of the neutron, a neutrally-charged particle in the nucleus of an atom.

1) Ernest B. Rutherford

               In 1897 the electron with a negative charge was discovered by J.J. Thompson and it seemed to orbit around the nucleus. Later, in 1918, Ernest Rutherford made the discovery of a positively-charged proton within an atom that seemed to cancel out the negativity of the electron, creating a neutral atom. After all of these findings, many thought that this was the make-up of an atom, just the protons and electrons, because they did cancel out each other to make a neutral charge. All of this information still didn’t stop Ernest Rutherford from contemplating another part of the atom. In 1920, he theorized that there was a neutral particle in the atom with around the same mass of a proton. His reasoning for this was because of the atomic number and the atomic mass. The atomic number of an atom is the number of protons it contains while the atomic mass is the mass of the nucleus. He was finding that the atomic mass was usually greater than the atomic number, demonstrating that there was something left to discover.
 2) James Chadwick

               In 1932, a scientist by the name of James Chadwick decided to put a decade of theory to the test and prove that there really was another neutrally-charged particle in the atom. He performed tests on a new type of radiation that had been puzzling scientists for years. It was previously mistaken as “gamma rays” (a form of radiation consisting of high-radiation photons) but Chadwick was out to prove this was not true. This type of radiation was electrically neutral and was discovered in 1930, just before it was used in Chadwick’s famous experiment. The radiation seemed to be coming from the nuclei of light elements that had been exposed to other types of radiation. At this time, many scientists had been thinking that they had found new types of particles but most of them turned out to be clusters of already known particles. Because of this, many thought that Chadwick was wrong and was just dealing with the known “gamma rays” which have no mass. In order to prove them wrong, Chadwick tried to determine the new particle’s mass and if it was approximately equal to that of a proton.
              Although this thought may sound easy, it was not. A subatomic particle is not something someone can just place on the scale and weigh. But, Chadwick came up with a solution. The masses of the nuclei of many elements were already known at the time and techniques for measuring the speed of the fast-moving nucleus had already been developed. So, he decided to force the mysterious new particles into samples of selected elements. He thought that when a direct collision occurred between the new particle and the nucleus of one of the target atoms, the nucleus would be knocked out of the atom, and he would measure the velocity.

              After all of this information, you are probably thinking, why is this important? Well, the discovery of the neutron helped us to understand the make-up of the atom. The neutron actually plays a big role in the stabilization of the atom, equal to that of even a proton. Also, neutrons play an important role in the process of creating nuclear explosions and nuclear energy. This is because the bombardment of high-energy neutrons is how a scientist can split an atom. 


Works Cited:


"Chadwick Discovers the Neutron 1932." PBS: A Science Odyssey. WBGH Educational
       Foundation, 1997. Web. 3 Oct. 2010. <http://www.pbs.org/wgbh/aso/
       copyright.html>.



"Chadwick's Experiment to Discover the Neutrons." Major and Minor Worlds. N.p.,
       n.d. Web. 3 Oct. 2010. <http://library.thinkquest.org/C001124/gather/
       aexp.html>.



Crowell, Benjamin. "The Discovery of the Neutron." Lectures in Physics. N.p.,
       n.d. Web. 31 Mar. 2006. <http://www.vias.org/physics/bk2_05_05.html>.



"James Chadwick." The History of Computing Project. N.p., 21 Mar. 2010. Web. 3
       Oct. 2010. <http://www.thocp.net/biographies/chadwick_james.htm>.



McPhee, Isaac M. "The Discovery of the Neutron: James Chadwick's Remarkable
       Experiment." 
Suite 101. N.p., 27 Feb. 2008. Web. 2 Oct. 2010.
       <http://www.suite101.com/content/the-discovery-of-the-neutron-a46060>.



Trinh, Hoc. "James Chadwick and His Discovery of the Neutron." Helium. N.p.,
       n.d. Web. 3 Oct. 2010. <http://www.helium.com/items/
       216709-james-chadwick-and-his-discovery-of-the-neutron>.



Pictures:

1)  Ernest Rutherford. N.d. N.p., n.d. Web. 3 Oct. 2010. 
         <http://3.bp.blogspot.com/_mg678rIGDbY/R2b0wHtaV6I/AAAAAAAAAAU/A-03hJoSR1A/
           s320/ernest_rutherford2.jpg>.

2) Corbis, J. English Physicist James Chadwick. N.d. Wired. N.p., n.d. Web. 3 Oct. 
         2010. <http://www.wired.com/science/discoveries/news/2009/02/dayintech_0227#>.

3) Hamilton, Calvin J. James Chadwick's Experiment. N.d. Solar Views. N.p., n.d. 
        Web. 3 Oct. 2010. <http://library.thinkquest.org/C001124/gather/ 
        aexp.html>.

Video:

Discovery of NeutronsTutor Vista. N.p., n.d. Web. 3 Oct. 2010.
        <http://www.youtube.com/watch?v=HnmEI94URK8>.

Saturday, September 11, 2010

Cotton Candy Chemistry

Description

Cotton candy, a delicious sweet treat, commonly found at a baseball game, is a very fun object to experiment with. It has many physical properties that are apparent to the naked eye, but also some that need physical testing to prove. Also, some very interesting chemical reactions occurred.


Physical Properties:


The amount that we used for each experiment was not exact, but it was about this amount each time.

- Soft
- Malleable
- Blue in color
- Sticky
- Dissolves in water



Chemical Properties:

We did multiple tests and they proved many chemical properties of cotton candy.

1. Cotton candy is NOT flammable
We held the flame to the cotton candy and although it melted, it did not produce it's own flame, demonstrating that it is not flammable.


2. Cotton candy has an odor of sugar and tastes sweet. We obviously tested this one, because of how amazing cotton candy is! Christina and I smelled it and it had a sugary smell and Christina tasted it and it was sweet like sugar.

3. When set on fire, cotton candy crystallizes. We set the cotton candy on fire and although it did not maintain its own flame, it crystallized into a thicker solid. 






4. When heated, the cotton candy first forms a liquid, shown below:




-Then it changes color into a greenish blackish hue:






-Finally, when cooled, it forms a hardened black and green crystal. This demonstrates a chemical change because of the change in color.




5. Finally, we performed an experiment with water, yeast, and cotton candy. First, we combined water and yeast in a plastic bottle:






-Then we put the cotton candy into the bottle and placed a plastic bag on the top to capture any gas that could possibly be formed:




-Next, we waited and checked it every five minutes and within 10 minutes, it formed bubbles and a new gas, what we thought was carbon dioxide. The reason this happened was because the yeast ate away the sugars and produced a gas:






-Next, to prove that this was carbon dioxide, we did yet another test. I know that some fire extinguishers are made up of liquid carbon dioxide that comes out as a gas so to prove that this was also carbon dioxide, we lit a match and stuck it in the bottle of gas:





-As you can see from the video above, this gas was indeed carbon dioxide. This whole experiment showed that yeast and water combined with the sugars of cotton candy to create a whole new gas, making it a chemical change.