Percent of Oxygen in Air Lab



Percent of Oxygen in Air Lab

Objective: The air is made up of a mixture of gases. Nitrogen and oxygen are the most abundant of those gases. Oxygen is used to form minerals on the earth’s surface, for animals in respiration, in all living cells for cellular respiration and in the burning of fuels. In this investigation, we will experiment to determine the percent of oxygen in the air as it is burned up during combustion.

Problem: When you breathe deeply, are you breathing in oxygen? How much of the air that you breathe is made up of oxygen?

Safety:

MUST WEAR GOGGLES

Long hair needs to be tied back.

No messing around with the fire.

Materials:

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Procedure:

1. Fill the test tube provided full (level) of water then pour the water into a graduated cylinder to measure the volume of the water in the test tube. Record this volume in the cart below as “Original Volume”.

2. Pour this water into the Petri dish.

3. Place penny with candle in Petri dish.

4. Light the candle and quickly put the upside-down test tube over the burning candle so that the mouth of the test tube is under water.

5. As the flame burns and oxygen is used, the water will rise into the test tube to fill the space left by the oxygen.

6. When the candle burns out, mark the level of the water on the test tube with the marker.

7. To figure the volume of the oxygen used, fill the test tube to the mark (this is the amount of air in the upside-down test tube), find the volume and subtract the volume from the original volume to find the oxygen volume (volume of oxygen burned and replace by water).

8. Repeat for 2 more trials, and record this data in the chart below.

9. Calculate “Percent of Oxygen” by dividing the “Volume Oxygen” by the “Original Volume” and multiplying by 100.

Volume of Oxygen

_______ X 100 = Percent of Oxygen

Original Volume

10. Total and average the “Percent of Oxygen” for the three trials.

|Trial # |Original Volume - |Volume of Water = |Volume of Oxygen |Percent of Oxygen % |

| | | |X 100 = | |

|1 | | | | |

| | | | | |

|2 | | | | |

| | | | | |

|3 | | | | |

| | | | | |

| |Total: | |

| | | |

| |Average: | |

| | | |

|Tables # |Percent of Oxygen % |

|1 | |

| | |

|2 | |

| | |

|3 | |

| | |

|4 | |

| | |

|5 | |

| | |

|6 | |

| | |

|7 | |

| | |

| | |

| | |

|Class Average | |

Conclusions:

In the space above summarize this lab, be sure to illustrate your summary.

1. What does the candle flame do?

2. Why does the water go up into the test tube as the candle burns out?

3. How might the percent of oxygen vary from a greenhouse (filled with plants) to a bag filled with air exhaled by you?

4. How would your percent of oxygen calculation be different if you:

A. Used a larger test tube?

B. Used a larger candle?

5. Analyze and discuss the class data. What is the range of calculated values? What is the average? How does the class average compare with the "correct" value for oxygen percentage in the atmosphere? Identify at least two (2) potential sources of error in your results and the class results.

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