Thursday, November 11, 2010

Question #18

18) What is the explanation for the discrete lines in atomic emission spectra?  How did this affect the model of the atom?

The discrete lines in the atomic emission spectra is from light emitted from the atoms transition back to the ground state from its excited state.  The atom gains this excited state when current flows through the atom and gains a brief potential energy.  Using an atom this light is split into different frequencies, or colors, of light in discrete lines.  This showed us that electrons must be in specific energy levels in the space of the atom.

Wednesday, October 6, 2010

Thomson's Cathode Ray Tube

The Cathode Ray Tube

The cathode ray, even though not invented by the physicist J. J. Thomson, was perfected by him.  He made a model almost identical to the one in the image above.  He did this by getting a glass tube and inserting wires into two of the sides of the tube.  Once attaching these wires to metal discs, and connecting them to a high voltage he pumped the air inside the glass tube to a very low pressure.

First Experiment
In Thomson's first experiment, he was determined to find out wether or not it was possible to separate the ray itself and the magnetic charge of the particles in the ray.  To do this, Thomson set up his cathode ray with electrometers on the other side of a metal cylinder, which he had cut a slit in.  When he applied a magnet to the ray the electrometers read nothing.  This showed the Thomson that the ray had moved with the magnet and was effected by its magnetic field.  He later concluded that this proved that the ray and its negative electronic charge in inseparable.

This effect would have looked similar to this:

Second Experiment
For his second experiment, Thomson set his cathode ray up in a similar way as before in his first experiment.  This time however he set out to prove that the cathode ray carried an electronic charge.  After improving his vacuum in the tube he set up two aluminum plates that, when connected to a battery, formed an electric field.  When he attached the plates to a battery, making the top negative and the bottom positive, the cathode ray bent downwards away from the negative side.  This effect was also reversed when the positive and negative sides were changed.  This experiment proved that the particles in the cathode ray were negatively charged

The results of this experiment would look like this:

Third Experiment
In his last experiment Thomson decided to try to find the nature of the particles in the cathode ray.  By using lots of different gasses inside the tube, different types of glass, and changing the strength of the electric charge he set out to find out more about the particles.  He discovered the charge to mass ratio of these particles was a thousand times lower than the hydrogen atom.

A summery of these experiments using the cathode ray would be similar to this:

The importance and significance of Thomson's work with the cathode ray was due to the fact that the particles that he had discovered were smaller than any element in the world.  At this period of time no other subatomic particle and been discovered so the news of Thomson's discoveries was shocking.  Also a popular scientist that had come before Thomson named Dalton had said in his atomic theory that there was no particle smaller than element.  Thomson's work proved him wrong.

Works Cited

  • Cathode Ray Tube . Youtube. N.p., n.d. Web. 6 Oct. 2010. <‌watch?v=7YHwMWcxeX8>.
  • Dchummer. Cathode Ray Tube . Youtube . N.p., n.d. Web. 6 Oct. 2010. <‌watch?v=O9Goyscbazk&feature=related>.
  • “Experiments with cathode rays  .” Wikipedia . N.p., n.d. Web. 6 Oct. 2010. <‌wiki/‌File:JJ_Thomson_exp2.png>.
  • “Famous Experiments: Cathode Rays.” Physics LAB . N.p., n.d. Web. 6 Oct. 2010. <‌Document.aspx?doctype=3&filename=Magnetism_CathodeRays.xml>.
  • “J. J. Thomson .” wikipedia . N.p., 6 Oct. 2010. Web. 6 Oct. 2010. <‌wiki/‌J._J._Thomson#Experiments_with_cathode_rays>.
  • “J. J. Thomson’s Cathode Ray Experiment .” Experiment-reasourses . N.p., n.d. Web. 6 Oct. 2010. <‌cathode-ray.html>.
  • “Thomson’s Experiment .” Think Quest . N.p., n.d. Web. 6 Oct. 2010. <‌19662/‌low/‌eng/‌exp-thomson.html>.
  • 3 experiments, 1 Big Idea . N.p., n.d. Web. 6 Oct. 2010. <‌history/‌electron/‌jj1897.htm>.
  • Wordle . N.p., n.d. Web. 6 Oct. 2010. <‌create >.

Sunday, September 12, 2010

Copper Pot, by Nick I

For my house hold object I chose a copper pot.  The copper pot is completely made out of copper, therefore i thought that it would be good to observe and record the properties of.  Also I decided that i would look for properties that would benefit people that used copper in their day to day life.

Physical Properties 

1.  Malleability- Copper is a very malleable metal and is shown to be by the making of this bowl. you can observe the markings on the walls of the bowl as examples of this malleability.

2. Conductivity- Copper is used in electrical wires around the world because of its ability to be conductive.

3. Brown color- The bowl has a brownish gold color to it which is from the copper.

4. Lustrous- The bowl has is shiny and reflects light which is also another quality of the copper.

5. Density- 8.92 grams per cubic centimeter.

Chemical Properties

1.The copper bowl is most stable at its oxidized state and if it is not cleaned frequently will form a layer of copper oxide over the walls of the bowl. The copper oxide can appear in two different forms, one being a dark tarnished brown color or a patchy teal.  This is caused by the oxygen bonding with the copper.

2. When the inside of the bowl is washed with lemon juice and salt the copper oxide washes away to show the true bright lustrousness of the copper element.  This is caused by the abrasion of the salt and the acidety of the lemon juice.

3. Adding vinegar to copper also cleans the copper oxide off but at the same time speeds up the process of becoming oxidized again. For example I used a test strip of copper and dipped it in store bought vinegar. the next day it had a dark teal rust-type material of the section of copper that had been submerged in vinegar.

4. After poring three egg whites into the bowl and stirring them for three minutes the egg whites began to stiffen much quicker than in a normal plastic bowl.  This happens because the copper causes the proteins in the egg white to coagulate much quicker.

5. The copper is very stable causing it to stay in the same state instead of either dissolving or breaking down into multiple elements.  The copper oxide helps to protect the bowl and keep it in its original form despite the fact that copper is a soft metal.

From these experiments and observations, i have concluded that copper is a very useful element. Not only is it easily shaped into different objects but when in is being used as one of these objects it is very useful and helpful.

Works Cited