1. Role of Buffers

2. 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. Introduction Journals and Snapshots Note: You may want to take a snapshot of the first page of this 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

3. 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

4. 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

5. This image is a reminder to tap to take a snapshot of the page after you have entered your response. Self-Check 1.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

6. 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

7. 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

8. Materials and Equipment Collect 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

9. 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 Challenge A. 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. Role of Buffers

10. Equipment Setup 1.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 Role of Buffers

11. Prediction 1.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

12. Collect Data: Water + Vinegar 1.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

13. 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: 1.Tap to open the tools palette. 2.Tap and then tap a data point. 3.Tap or to select nearby data points. Role of Buffers

14. 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

15. Setup: Club Soda + Vinegar 1.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

16. Collect Data: Water + Vinegar 1.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

17. 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: 1.Tap to open the tools palette. 2.Tap and then tap a data point. 3.Tap or to select nearby data points. Role of Buffers

18. 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.

19. Data Analysis 1.Calculate the change in pH for each experiment and complete the data table below. Role of Buffers

20. Analysis 1.How well did the results for water + vinegar match your predictions about a change in pH? Role of Buffers

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

22. Synthesis 1.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

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

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

25. 4.Why are buffers important in biological systems? Role of Buffers Synthesis

26. 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

27. 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 Role of Buffers Multiple Choice

28. 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 Role of Buffers Multiple Choice

29. 4.Which of the following is most acidic? a)vinegar b)club soda c)water d)human blood Role of Buffers Multiple Choice

30. You have completed the lab. Congratulations! Please remember to follow your teacher's instructions for cleaning-up and submitting your lab. Role of Buffers

31. Images are taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons. http://www.freeclipartnow.com/office/paper-shredder.jpg.html http://commons.wikimedia.org/wiki/File:Redbloodcells.jpg References Role of Buffers