Dilution of polluted water lab

Dilution of Polluted Water Lab

Purpose: All human activity and many natural processes produce pollution. Pollution is a generic term for contamination from any activity that has a negative impact on the environment or human health. Pollution can travel by three major pathways: air, water, and land. Since it can travel using several different methods, it can be very difficult to remove pollution completely once an area has been contaminated. Sometimes even very small amounts of pollution can have a negative effect on people, animals and plants, so detecting and removing it can be complicated and expensive. In this activity, we will take a sample of a chemical and treat it as if it is ‘polluted water’. We will then dilute the sample five times, decreasing its concentration by ten times for each step, all the way down to one-hundred thousandth of the original concentration. Finally, we’ll test each sample with a drop of chemical indicator to attempt to detect ‘pollution’ at each concentration.

Directions:

1. You should have six test tubes in a test tube rack.

2. Obtain the solution representing the “polluted water” and place 10 mL of the “water” in a graduated cylinder.

3. Pour the 10mL of “polluted water” in your first test tube on left. Rinse out graduated cylinder thoroughly.

4. Using a plastic pipette, remove “polluted water” from test tube #1 and measure 1 mL in your graduated cylinder.

5. Transfer this 1 mL to test tube #2 and rinse out your graduated cylinder.

6. Using graduated cylinder measure 9mL of “clean water” and add to test tube #2. This dilutes the polluted sample to ten times less concentrated.

7. Then take repeat the steps and measure 1mL of “polluted water” from test tube #2 and add to test tube #3. Rinse out graduated cylinder.

8. Add 9mL of clean water to test tube #3.

9. Repeat these steps until you are at test tube #6.

10. After you have your “polluted water” samples in test tube #1 through #6, take 1 drop with your pipette and test on pH paper. Record the color and pH number.

11. Then add 1 drop of indicator to each of the test tubes and record the color of each. You may swirl the test tube to mix the indicator.

Data Table:

	Test tube #1	Test tube #2	Test tube #3	Test tube #4	Test tube #5	Test tube #6
pH paper color
pH numerical value
Color with indicator

Analyze:

1. What trend did you notice in the colors of the test tubes after the indicator was added and the test tubes became less concentrated and more dilute? Why do you think this happened?

2. What happened to the pH value from test tube #1 to #6? What is happening to the solutions? Did it ever become “neutral”?

3. Do you think that you can remove pollution from water by simply diluting it? Explain why or why not using your evidence.