Role of Buffers

The Snapshot button is used to capture the screen.

The Journal is where snapshots are stored and viewed.

The Share button is used to export or print your journal to turn in your work.

IntroductionJournals and Snapshots

Note: You may want to take asnapshot of the first page ofthis lab as a cover page for your journal.

Each page of this lab that contains the symbol

Should be inserted into your journal. After completing a lab page with the snapshot symbol, tap (in the upper right hand corner) to insert the page into your journal.

Role of Buffers

Lab Challenge• What does a "buffer" do?

• Why are buffers important to cells?

• What role do buffers play in maintaining the health of organisms?

Role of Buffers

Background• All living creatures, even single-celled organisms, must maintain very stable

internal conditions in order to survive. For example, organisms must maintain healthy levels in their temperature, pH, and water content.

• A stable level in metabolic conditions is called homeostasis. All multicellular organisms contain complex buffer systems that allow the organism to maintain stable pH, avoiding excessive acidity or alkalinity.

• A buffer is a solution that resists changes in pH. Buffers are usually mixtures of a weak acid and their salts.

• In the human body, pH is maintained by many substances including proteins, phosphate, and carbonic acid-bicarbonate buffer. The carbonic acid-bicarbonate buffer system is important in maintaining blood pH at stable and healthy levels.

Role of Buffers

This image is a reminder totap to take a snapshot of the page after you have entered your response.

Self-Check1. Which is NOT true of buffers?

a) They help establish homeostasis.

b) They resist changes in pH.

c) They help increase pH.

d) They're found inside all multicellular life.

Role of Buffers

Self-Check

2. Why is the carbonic acid-bicarbonate buffer system important to human health?

a) It maintains blood pH at a stable level.

b) It prevents heartburn.

c) It lowers blood pH to prevent infections.

d) It raises blood pH to reduce clots.

Role of Buffers

Safety• Use all standard laboratory safety procedures.

• Keep water away from electronic equipment.

• Before disposing of chemicals and solutions, ask your teacher for instructions.

Role of Buffers

Materials and EquipmentCollect all of these materials before beginning the lab.• pH sensor• Graduated cylinder, 10 mL• 250 mL beaker• Club Soda, 200 mL• Vinegar, 5% acetic acid, 20 mL

• Large base and support rod• Utility clamp• Magnetic stirrer and spin bar• Water, 200 mL• Distilled water, 1 L

Role of Buffers

The steps to the left are part of the procedure for this lab activity. They are not in the right order. Determine the correct sequence of the steps, then take a snapshot of this page.

Sequencing ChallengeA. Add vinegar to club soda in the beaker, then measure the pH.

B. Add vinegar to water in the beaker, then measure the pH.

C. Clean up all materials according to your teachers instructions.

D. Gather all necessary materials together.

E. Analyze your results.

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Equipment Setup1. Connect a pH sensor to your SPARK Science

Learning System.

2. Put a spin bar and 100 mL of water into a 250-mL beaker and place the beaker on the magnetic stirrer and turn the stirrer on.

3. Use a clamp with a base and support rod to position the pH sensor inside the beaker without it touching the spin bar.

4. Pour 10 mL of vinegar into a graduated cylinder (do not pour it into the beaker yet).

Magnetic stirrer

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Prediction1. What do you predict will happen to the pH of

water if you add vinegar to it? (Tap the top box to enter your answer.)

2. What do you predict will happen to the pH of club soda if you add vinegar to it? (Tap the bottom box to enter your answer.)

After answering the questions, take a snapshot to journal your answers.

Role of Buffers

Collect Data:Water + Vinegar1. Tap to begin collecting

data.2. Record data for 30 sec,

then slowly pour the vinegar into the beaker.

3. Record pH data for another 10 seconds.

4. Tap to stop data collection.

Role of Buffers

5. Find the initial and final pH for the data run.*

6. Enter the initial/final pH in the data table, on the next page.

* To Find the X- and Y-Values of a Data Point:

7. Tap to open the tools palette.

8. Tap and then tap a data point.

9. Tap or to select nearby data points.

Role of Buffers

7. Enter the initial/final pH for the Water + Vinegar run in the data table to the left.*

* To Enter Data into a Table: 1. Tap to open the Data

Table toolbar.2. Tap then tap a cell in

the data table to highlight it in yellow.

3. Tap to activate the text editor.

Role of Buffers

Setup: Club Soda + Vinegar1. Dispose of the water/vinegar as directed by your

teacher.

2. Rinse the beaker and graduated cylinder and pH probe very thoroughly with distilled water.

3. Pour 100 mL of club soda into the beaker on top of the magnetic stirrer. Turn on the stirrer.

4. Pour 10 mL of vinegar into a graduated cylinder (do not add it to the beaker yet).

Role of Buffers

Magnetic stirrer

Collect Data:Water + Vinegar1. Tap to begin collecting

data.2. Record data for 30 sec,

then slowly pour the vinegar into the beaker.

3. Record pH data for another 10 seconds.

4. Tap to stop data collection.

Role of Buffers

5. Find the initial and final pH for the data run.*

6. Enter the initial/final pH in the data table, on the next page.

* To Find the X- and Y-Values of a Data Point:

7. Tap to open the tools palette.

8. Tap and then tap a data point.

9. Tap or to select nearby data points.

Role of Buffers

Role of Buffers

7. Enter the initial/final pH for the Water + Vinegar run in the data table to the left.*

* To Enter Data into a Table: 1. Tap to open the Data

Table toolbar.2. Tap then tap a cell in the

data table to highlight it in yellow.

3. Tap to activate the text editor.

Data Analysis1. Calculate the change in pH for each experiment and complete the data

table below.

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Analysis1. How well did the results for water + vinegar match your predictions

about a change in pH?

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2. How well did the results for club soda + vinegar match your predictions about a change in pH?

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Analysis

Synthesis1. Consider the definition of a buffer.

a) Which starting liquid made a better buffer: distilled water (pure water with no dissolved minerals) or club soda (containing sodium bicarbonate and carbonic acid)?

b) How does your experiment show this?

Role of Buffers

2. Tap water contains minerals. What results would you get if you repeated this experiment using tap water instead of distilled water?

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Synthesis

3. Explain how the club soda in this experiment is representative of the buffering ability of blood?

Role of Buffers

Synthesis

4. Why are buffers important in biological systems?

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Synthesis

Multiple Choice

1. What property of a living organism indicates a stable internal environment?

a) metabolism

b) homeostasis

c) buffer system

d) respiration

Role of Buffers

2. Which of the following would be the best buffer?

a) strong acid

b) strong base

c) salt with pH of 7.0

d) weak acid and salt combination

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Multiple Choice

3. Which of the following would indicate a strong acid?

a) pH 7.0

b) pH 14.0

c) pH 1.5

d) pH 7.5

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Multiple Choice

4. Which of the following is most acidic?

a) vinegar

b) club soda

c) water

d) human blood

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Multiple Choice

You have completed the lab.Congratulations!

Please remember to follow your teacher's instructions for cleaning-up and submitting your lab.

Role of Buffers

Images are taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons.

http://www.freeclipartnow.com/office/paper-shredder.jpg.htmlhttp://commons.wikimedia.org/wiki/File:Redbloodcells.jpg

ReferencesRole of Buffers