Exercise 1: Water and its Unique Properties
Data Table 1.Needle Observations.
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Vertical Observations
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Horizontal Observations
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In the vertical position, the needle sinks to the bottom of the beaker, landing in a horizontal position.
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In the horizontal position, the needle floats on top of the water, with the water "bending" slightly above the needle.
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Data Table 2. Paper Clips Needed to Break Surface Tension.
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Prediction
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Result
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__9___ Paper clips
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_77__ Paper clips
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Data Table 3. Drops of Water.
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Prediction
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Result
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__17__ Drops of water
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_38_ Drops of water
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Data Table 4. Part 4 Observations.
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Observations
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The capillary action of the celery has allowed it to draw up some of the red colored water. This has resulted in a slight red coloration of the stalk and a fairly significant red coloration of the leaves.
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Questions
A. How did the experiment in Part 1 demonstrate surface tension? Use your experiment observations when answering this question.
B. In Part 1, when adding the needle to the water, which approach worked best to balance the needle on the water-the vertical or horizontal placement? Explain your answer.
C. In Part 2, how did your paper clip estimation compare to your paper clip results?
D. In Part 3, how were the properties of adhesion and cohesion demonstrated in the experiment?
E. How did the activity in Part 4 demonstrate capillary action? Explain your answer using your experiment results and observations.
Exercise 2: Testing Common Household Materials for pH Values
Data Table 5. pH Observations.
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Well Plate
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Item Tested
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Commercial pH strip
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Homemade pH strip
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Color
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pH
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Color
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pH
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1
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HCl (hydrochloric acid)
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Pink
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1
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Deep red
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2
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2
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NaOH (sodium hydroxide)
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Green
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9
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Deep blue
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12
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3
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Distilled water
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Light blue or light purple (no noticeable change)
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7
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Yellow (no noticeable change)
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7
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4
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Dish Soap (Palmolive)
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Pink
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1
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Orangish-yellow
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6
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5
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Lemon Juice
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Pink
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1
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Orange
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4
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6
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Creatine Drink
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Pale Purple
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3
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Orangish-yellow
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6
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7
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Soy Sauce
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Orangish-brown
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12
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Orangish-yellow
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6
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8
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Milk
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Light blue or light purple (no noticeable change)
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7
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Greenish-blue
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9
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9
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Pine-Sol
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Pink
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1
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Orangish-yellow
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6
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10
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Leather Cleaner
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Blueish-green
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9
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Green
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8
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11
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Furniture Oil Polish
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Pale blue
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4
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Yellow (no noticeable change)
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7
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12
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Hand Soap
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Pale purple
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3
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Yellow (no noticeable change)
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7
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Data Table 6. Analysis of Results.
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Well Plate
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Item Tested
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Acid/Base/
Neutral?
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Explanation:
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1
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HCl(hydrochloric acid)
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Acid
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2
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NaOH(sodium hydroxide)
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Base
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3
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Distilled water
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Neutral
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4
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Dish Soap (Palmolive)
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Acid
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5
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Lemon Juice
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Acid
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6
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Creatine Drink
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Acid
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7
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Soy Sauce
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Acid?
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8
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Milk
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Base
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9
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Pine-Sol
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Acid
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10
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Leather Cleaner
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Base
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11
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Furniture Oil Polish
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Neutral?
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12
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Hand Soap
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Neutral?
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Questions
A. Compare and contrast the results between the commercial and homemade pH test strips. Which test strips were more accurate? Explain your answer.
B. Why is the pH scale important in science? Give several examples of scientific applications.
C. What information about a chemical can be inferred from knowing its pH value?
D. If a chemical has a pH of 3, how could you change its pH value to be more basic?
Exercise 3: Buffers in a Living System
Data Table 7.pH Change of Buffered and Un-buffered Solutions.
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Un-buffered Solution
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Buffered Solution
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Initial pH
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7
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8
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+ 3 drops HCl
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6
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8
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+ 6 drops HCl
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5
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8
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+ 9 drops HCl
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4
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8
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+ 12 drops HCl
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4
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7.5
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+15 drops HCl
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4
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7.5
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+18 drops HCl
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4
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7
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Data Table 8. Graph of pH Changes.
Questions
A. Analyze the results of your experiment. Did the buffer resist changes in the pH? Explain your answer using your experiment results.
B. Research the bicarbonate buffering system found in the blood stream. Write a paragraph or two discussing this system and how your breathing rate can cause acidosis and alkalosis.