Role of Buffers
Role of Buffers
Introduction
Journals and Snapshots
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.
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.
Note: You may want to take a
snapshot of the first page of
this lab as a cover page for
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
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.
This image is a reminder to
tap
to take a snapshot
of the page after you have
entered your response.
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 Equipment
Collect all of these materials before beginning the lab.
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pH sensor
Graduated cylinder, 10 mL
250 mL beaker
Club Soda, 200 mL
Vinegar, 5% acetic acid, 20 mL
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Large base and support rod
Utility clamp
Magnetic stirrer and spin bar
Water, 200 mL
Distilled water, 1 L
Role of Buffers
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.
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.
Role of Buffers
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
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
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
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 YValues 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
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 + 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).
Magnetic stirrer
Role of Buffers
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
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 YValues 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
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
Data Analysis
1. Calculate the change in pH for each experiment and complete the data
table below.
Role of Buffers
Analysis
1. How well did the results for water + vinegar match your predictions
about a change in pH?
Role of Buffers
Analysis
2. How well did the results for club soda + vinegar match your predictions
about a change in pH?
Role of Buffers
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
Synthesis
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
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?
Role of Buffers
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
Multiple Choice
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
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
4. Which of the following is most acidic?
a) vinegar
b) club soda
c) water
d) human blood
Role of Buffers
Congratulations!
You have completed the lab.
Please remember to follow your teacher's instructions for cleaning-up and submitting
your lab.
Role of Buffers
References
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