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.