Thursday, January 27, 2011
Finish % oxygen in the Atmosphere lab into your notebook. Keep working on your earthmoon project quadrants due Friday, 2/4/2011.
Finding the Percentage of Oxygen in the Atmosphere
The atmosphere of the earth is composed of a mixture of gases. The two most abundant gases are nitrogen and oxygen. Oxygen also appears in the earth's crust combined with other elements to form minerals.
In this investigation, you will study how much of the air is consumed during combustion. By measuring volume, you will be able to determine the percentage of oxygen in the air.
What is the percentage of oxygen in the air?
Hypothesis- see board
Test- see board
Materials (per group)
400-mL plastic beaker
Flame source- from instructor
Large Petri dish
Wire or wood dowel Glass jar
Procedure- See diagram on board and set up from Demo
1. Light the candle and let a few drops of wax drop on the penny. Blow out the candle, and place the candle upright on the penny in the wax. The candle should stick to the penny. 2. Fill the test tube with water. Using the formula for a cylinder (eR2H) measure the volume of cylinder using a ruler and metric units and record it in the Data Table. The volume is also the volume of air in the jar at the start of the experiment.
2. Pour the water into the Petri dish. Carefully place the candle in the center of the dish. Fill dish until the candle floats but leave space so as NOT to overflow the dish when you place the jar over the candle.
3. Carefully light the candle, and invert the jar over the lighted candle. Make sure that jar rests on the piece of wire or wood so as not to for an airtight seal with bottom of the Petri dish. See Demo
As the candle uses the oxygen in the test tube, the candle will go out and water will be drawn into the tube to replace the oxygen.
5. When the candle goes out, carefully mark the level of the water on the jar with the glass-marking pencil. Remove the jar and find the height of the water, using cm. Calculate the volume of Water( this is also the volume of used up Oxygen) using (eR2H) with the new value of H and record in your data table.
6. Dry out your jar and dry off the candle and repeat the process for two more trials.
7. Determine the percentage of oxygen in air by using the formula below. Record this percentage in the Data Table.
% oxygen in air =
Volume of oxygen in the test tube
Total volume of air in test tube at start
DATA TABLE trial 1 trial 2 trial 3
Volume of Air in the jar at Start
Volume of water in jar Tube After Candle Goes Out
Volume of Oxygen (should be same as above)
Percentage of Oxygen in Air
1. Would the same result for the percentage of oxygen in air be obtained if a larger test tube was used? A larger candle?
2. Why does the water rise in the test tube as the candle goes out?
3. Nitrogen is the other major component of air (78.1%). What property of nitrogen have you discovered as a result of this experiment?
4. How much oxygen is present in 5 L of air?
Critical Thinking and Application
1. Why is oxygen such an important part of the earth's atmosphere?
2. Based on your observations, what is an effective method of putting out a small fire?
3. "As the altitude of an area increases, the density of the atmosphere decreases." How can this statement be used to explain why it is more difficult to breathe in
, which has an altitude of more than 1500 meters, than in Denver , which is at sea level? Houston
Here are the links to the SEEDS program website from Santa Clara University and the SMYSP website from Stanford University. Print out and complete the application if you are interested in trying out foer the programs. THe SEEDS application is due Feb. 4th , 2011; The SMYSP application is due Feb. 15th, 2011. Good Luck!!
Monday, January 24, 2011
Students should be in the production phase for the Earth/Moon project. Final quadrants will be due Friday Feb. 4th at the Begining of the period. This is a hard deadline, i.e. NO LATE ASSIGNMENTS beyond 2:45pm We will be working in class, during some of each period, but it needs to be worked on outside of class to ensure completion on time.
Friday, January 21, 2011
Read Earth science ch 11.1, pgs 270-7, and take notes on the atmosphere. Answer the following qustions into your notebook:* 1) What the layers of the atmosphere in order from lowest to highest and briefly describe each one? 2) Describe three ways energy from the sun can be transferred to the atmosphere of the earth.
Friday, January 14, 2011
Wednesday, January 12, 2011
Tuesday, January 11, 2011
Monday, January 10, 2011
You should be working on your research information for your quadrants for the Earth/Moon project 2011. Remember that all information needs to presented through some kind of visual representation on the final presentation. i.e. graph, T chart, flip book, Venn Diagram etc... Research packet notes and final work cited page drafts are due Friday 1/21/2011 Thank you!
Rough drafts for your posters are due next class and should include both a layout diagram and the information for your EQ and Pro's and Con's so that other groups can begin the generation of questions to ask you during out Bioethics symposium.