Saturday, December 11, 2010

If Your Cat Took Chemistry, Would She Eat This Stuff?

          For this blog, i decided to use a variety of products. I separated the products into three main categories. I tried to find a variety of items within each category in order to demonstrate that compounds are found in so many items. 


TLC Almay Longwear Makeup:
        1. zinc oxide  -   ZnO
Victoria Secret - Drenched in PINK: pretty and pure body lotion:
        2. sodium hydroxide  -   NaOH
Crest Whitening Dental Wraps:
        3. hydrogen peroxide  -  H2O2
Mary Kay Makeup Remover
        4. sodium chloride  -   NaCl
        5. potassium phosphate  -   K3PO4
Crest Whitening Toothpaste:
        6. sodium fluoride  -   NaF


Adora Calcium Supplement: 
        7. calcium carbonate  -  CaCO3
        8. magnesium oxide  -   MgO
Crystal Light Drink Mix - Raspberry Flavor:
        9. calcium phosphate  -   Ca3(PO4)2
Ramen Noodle Soup - Chicken Flavor
        10. potassium carbonate  -   K2CO3
        11. sodium phosphate  -   Na3PO4
        12. sodium carbonate -   Na2CO3
Slim Fast - French Vanilla: 
        13. magnesium phosphate  -   Mg3(PO4)2
        14. potassium iodide  -   KI
        15. chromium chloride:
                    - chromium (II) chloride  -   CrCl2
                    - chromium (III) chloride  -   CrCl3

Science Diet Sensitive Stomach Cat Food:
        16. potassium chloride  -   KCl
        17. copper sulfate:
                   - copper (I) sulfate  -   Cu2SO4
                   - copper (II) sulfate  -   CuSO4
        18. calcium iodate  -   Ca(IO3)2
        19. phosphoric acid  -   H3PO4
FortiDiet Hamster and Gerbil Food:
        20. cobalt carbonate
                   - cobalt (II) carbonate  -   Co2(CO3)3
                   - cobalt (III) carbonate  -   CoCO3
ProPlan Small Dog Biscuit:
        21. zinc sulfate  -   ZnSO4

Tuesday, November 9, 2010

Trimester 1 Exam Review Question #15

#15. Which would have the smallest radius: Na, I, and O? Explain your answer throughly.
                - Oxygen would have the smallest radius.


  Atomic radius is defined as one half of the distance between the nuclei of two atoms of the same element when the atoms are joined. The atomic radius decreases across periods because there are less electron shells to shield the attractive power of the nucleus. You add a proton each time you go across the period, making it have a more attractive power. The attractive power causes it to pull in the electron shells tighter, which decreases the radius. It increases down groups because each time you go down, a new energy level is added. This creates a new electron shell. The number of electrons outnumber the number of protons, which means the attractive force isn’t as great. This allows the shells to spread out more because it doesn't have the attractive force pulling it in, creating a larger radius. 

Oxygen would have the smallest radius because it has the smallest number of electron shells. This causes the positive charge to be greater and pull the electron shells closer, therefore decreasing the radius. Sodium has a larger radius than oxygen because it has more electron shells and a smaller attractive force, allowing the shells to spread out. This causes a larger radius. Iodine has a larger radius than oxygen because even though it has a very strong attractive force, the number of electron shells outnumbers the attractive force. This means the radius for iodine is larger because the all the shells spread out. 

Wednesday, October 6, 2010

Rutherford's Gold Foil Experiment


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                        Rutherford is best known for his gold foil experiment, which greatly contributed to the model of the atom as we know it today. His experiment introduced a new understanding about the atom, and proved his former teacher’s model incorrect. The gold foil experiment was conducted in 1909 at the University of Manchester by Geiger and Marsden, but his theory of the atom wasn’t complete until 1911 (4). 

Ernest Rutherford had the opportunity to study and research at a variety of colleges. At the colleges, he was able to make many discoveries that would assist him in his gold foil experiment. He studied radioactivity, which led him to discover alpha particles, the main focus in the gold foil experiment. Ernest Rutherford was born on August 30, 1871 in Spring Gold, New Zealand. He obtained his early education through government schools, and at the age of 16, he entered Nelson Collegiate School. In 1889 he was awarded a University scholarship to Canterbury College at the University of New Zealand. He graduated from Canterbury with a double major in mathematics as well as physical science. In the year 1849, he was awarded an 1851 Exhibition Science Scholarship that allowed him to study at Trinity College at the University of Cambridge as a research student. At Trinity College, he worked with J.J. Thomson in the Cavendish Laboratory, who would become a very important figure in the gold foil experiment (1). While working with Thomson, Rutherford studied radiation, which led to his interest in alpha particles. He was offered a job as a chemistry professor to be the Macdonald Chair of Physics at McGill University in Montreal. In 1898, he moved to Canada to take the job, where he continued to work with radioactivity. His research led him to discover that radioactivity was the "spontaneous disintegration of atoms" (2). Due to all the work he did at McGill University, he was awarded the Nobel Prize in Chemistry in 1908. In 1907, he succeeded Arthur Schuster at the University of Manchester, where he began an in-depth study of alpha particles (1). His research led him to discover that alpha particles cause a weak, but discrete flash when they strike a luminescent zinc sulfide screen (4). His research and findings about alpha particles would later prove to be very important in his gold foil experiment.

                                                      Ernest Rutherford (1)

Who was involved in the gold foil experiment?
Rutherford was credited for the gold foil experiment, but two other people played a important role in the experiment as well. Under the supervision of Rutherford, Geiger and Marsden performed the gold foil experiment. Hans Geiger, Rutherford’s partner, had worked with him at the University of Manchester since 1908, and Ernest Marsden was a student at the University of Manchester (4). Although J.J. Thomson wasn’t directly involved with the experiment, he played a key role, serving as the reason the experiment was performed. Rutherford was a former student of Thomson and highly looked up to him. The reason behind the gold foil experiment was to prove Thomson’s “plum pudding model” (5).  

                                                Rutherford and Geiger (2)

J.J Thomson’s “Plum Pudding Model”
The “plum pudding model” was J.J. Thomson’s theory of atomic structure that he developed in 1904 (3). His theory was that all the subatomic particles were spread evenly throughout the atom in one positively charged piece. In other words, negatively charged electrons were floating in a mass of positive charge (4).

Thomson believed the negative electron "plums" floated around in a large mass of positive         "pudding"  (3)

The experiment:
The gold foil experiment was ultimately performed in order to prove Thomson’s “plum pudding model”, although that was not the case. Just the opposite happened, proving the theory incorrect. The experiment consisted mostly of alpha particles and gold foil (5). An alpha particle is a helium nucleus released by radioactive substances (discovered when Rutherford was studying radioactivity). It is a fairly heavy, positively charged particle (6). To begin, polonium was put into a lead box that sent out alpha particles to a thin sheet of gold foil. The foil was then surrounded by a luminescent zinc sulfide screen that served as a backdrop for the alpha particles to appear on (4).  A microscope was placed above the screen so they could easily observe any contact made between the alpha particles and the screen. In order to see the light of the alpha rays more clearly, the experiment was performed in complete darkness. To begin the experiment, they aimed a beam of alpha particles at a piece of gold foil, and then observed the astonishing results (5).

A simple diagram of how the experiment was set up. (4)
            In order to prove Thomson’s “plum pudding model”, the alpha particles were supposed to go straight through the foil. Shockingly, although most alpha particles passed straight through the gold foil, some did not. A small amount of particles were deflected slightly from the straight path by only about one or two degrees. An even smaller amount of particles were reflected off the gold foil at very large angles, and some occasionally bounced directly back at the source (3). The fact that some particles bounced back at large angles was the most surprising factor of the whole experiment. They discovered that 1 in 20,000 particles would bounce back at approximately 90 degrees or more from the parent beam. Rutherford was so amazed by this outcome, he explained the result by saying, “It was as if you fired a 15-inch shell as a sheet of tissue paper and it came back to hit you.” (5).  

            Obviously, Thomson’s “plum pudding model” was proven incorrect. Thomson’s theory said that an atom was made up of empty space, but that couldn’t be correct if the particles had bounced back because they had to have hit something. Rutherford reasoned that the item that was hit must have been very small since the majority of the particles didn’t bounce off of it (5). Alpha particles are very heavy, and have a mass about 8,000 times that of an electron. The alpha particles were traveling at a very high speed when they hit the foil, so a strong force was necessary in order to redirect the alpha particles since they were already so heavy (6). The way and angles in which the alpha particles bounced off the foil indicated that the majority of the mass of an atom was concentrated in one small region, that Rutherford later called the nucleus (3). He reasoned that the nucleus held all the positive charge, while electrons occupied most of the atom’s space. In simpler terms, the atom was made up of mostly empty space, which was why the majority of the alpha particles passed through. The particles that were deflected must have hit something in order for it to bounce off. This item that the particles bounced off of was named the nucleus.

This model describes how some of the alpha particles passed straight through, and how others didn't. As seen in picture (b), some of the alpha rays hit the nucleus. Depending upon where the nucleus was hit, the angle from which it was deflected differed. (5)

1. An atom was much more than just empty space of scattered electrons. (as opposed to what the "plum pudding model" proposed)
2. An atom must have a positively charged center that contains most of its matter (5). 
                  - He called this dense, concentrated center the nucleus (4). 
3. The positively charged center (nucleus) was relatively small in reference to the total size of the atom (5). 

Importance/ Significance:
            Rutherford’s gold foil experiment proved the “plum pudding model” of the atom incorrect, which allowed for a more complete understanding of the atom. His discovery of the nucleus and atomic structure was refined by Niels Bohr. Niels Bohr designed a model of the atom based off of Rutherford’s experiment, which is often referred to as the Rutherford Bohr model. This is so important because this is the basic atomic model that is still being used toady (3). The discovery of the nucleus and atomic model also allowed for the development of nuclear physics (4). This highly contributed to discoveries of the atomic and nuclear bomb, as well as organizing the Manhattan Project (2). In conclusion, Rutherford’s gold foil experiment contributed to what is today’s atomic model, and there has yet to be another discovery to disprove it.

 (1) “Ernest Rutherford – Biography”. 5 Oct 2010 - bio.html
(2)  “Ernest Rutherford, first baron (1871 – 1937)”. October 5, 2010
(3) Pestka, Jessica. “About Rutherford’s Gold Foil Experiment”. October 5, 2010
(4) “An Overview of Rutherford’s Gold Foil Experiment”. October 5, 2010
(5)“The Gold Foil Experiment”. October 5, 2010

Saturday, September 11, 2010

Chemical and Physical Properties of Cotton Candy

       Cotton candy is a sweet treat that is often enjoyed at fairs, circuses, and baseball games. When a person first looks at cotton candy, it does not come to mind that there are tons of physical and chemical properties. Although physical properties are more evident than chemical properties, there are still many chemical properties, if not more. 

This is approximately the amount of cotton candy used for each experiment performed. 
Physical Properties:
1.  Blue in color
2.  Malleable
3.  Sticky
4.  Solid state
5.  dissolves in water
We began by putting water in a bowl,
 and taking the sample size of cotton candy.
Next, we placed the cotton candy in the
bowl, and it immediately dissolved.

Chemical Properties:
1. Not flammable
We placed a piece of cotton candy on the ground, and tried lighting it on fire. We discovered that cotton candy is non-flammable because although the cotton candy did begin to melt, the flame did not stay on the cotton candy. We had to continue lighting the piece of cotton candy on fire, proving it is not flammable. 

2. Smells like sugar and tastes sweet
- Obviously, by smell, cotton candy smells sweet like sugar. We smelled the cotton candy, knowing that odor was a chemical property. It is a chemical property because it has the ability to react and change odor when two substances are mixed together.
- I tasted the cotton candy, and it had a sweet taste. Once again, from our knowledge of chemistry, we knew that sweet taste was a chemical property because it has the ability to undergo a chemical change with the silva and taste buds. 

3. Cotton candy crystalizes when it is set on fire.
Although cotton candy is not flammable, when trying to light it on fire we discovered another chemical change. When we continued holding the flame to the cotton candy, it wouldn't break down anymore. It created a solid substance that crystalized. This is due to all the sugar in the candy. 
4. When the cotton candy is heated on a stove, it produces a change in color.
First, we began by putting the
cotton candy in a pan and heating
it over a stovetop. When we did
that, it immediately started to
After letting the cotton candy cook for
about 5 minutes, it began turning a
greenish brown color. The color change
 from blue to greenish brown indicates a
chemical property.  
Once cooled, it then returns to a solid
and the final solution looks like this.
The middle is a dark brown, and
the sides are green.  
5. When combined with yeast and warm water, a new gas is produced.
         - The new gas produced it carbon dioxide. We supported this through two different experiements, both dealing with the plastic bottle, water, yeast, and cotton candy. One deals with the plastic bottle and bag as shown directly below, and the other has to do with fire.

         We began by mixing warm
           water with yeast and pouring
          it into a plastic water bottle. 
We then added in the cotton candy
and attached a plastic bag on the
top to trap any gas that may form. 
Over time, bubbles began to
form above the liquid mixture.
The plastic bag attached to
the top inflated, which was
 filled with the gas, carbon dioxide.  

As our second experiment, I researched that carbon dioxide, which is in many fire extinguishers, has the ability to put out fire. To prove that the gas was carbon dioxide, we decided to light a match and put it near the bottle as carbon dioxide is being released. If the flame went out, then we could conclude it was carbon dioxide. To perform this experiment, we quickly took off the plastic bag, lit a match, and placed it just close enough to the rim of the bottle. This allowed the carbon dioxide to reach the match and put out the flame within seconds, proving that the gas is carbon dioxide.

    - Research about carbon dioxide having the ability to put out a fire.
    - Sugar, yeast, water, and carbon dioxide experiment: