LESSON PLAN
Name: Johanna Villalon
Title
of lesson: Buffers
Date
of lesson: 5th six weeks
Length
of lesson: 1 hour
Description
of the class:
Name
of course: Chemistry
Grade
level: 9th
Honors
or regular: Regular
Source
of the lesson:
http://dante.edison.edu/course_material/bsc1010/03B-DisociationWaterMolecu.ppt
http://www.wwnorton.com/chemistry/tutorials/ch16.htm
TEKS
addressed:
(1) Scientific
processes. The student, for at least 40% of instructional time, conducts field
and laboratory investigations using safe, environmentally appropriate, and
ethical practices. The student is expected to:
(A) demonstrate safe practices during field and laboratory
investigations; and
(B) make wise choices in the use and conservation of resources
and the disposal or recycling of materials.
(2) Scientific
processes. The student uses scientific methods during field and laboratory
investigations. The student is expected to:
B) collect data and make measurements with precision;
(D) organize, analyze, evaluate, make inferences, and predict
trends from data; and
(E) communicate valid conclusions.
(14) Science concepts. The student knows the properties and behavior of acids and bases. The student is expected to:
(D) describe effects of acids and bases on an ecological system
I. I.
Overview
Students will
understand the importance that buffers bring to organisms and to the ecosystem.
They will investigate how a buffer helps balance the addition of an acid or
base to a substance and will further investigate their buffering capacity. This
lesson should be taught before the benchmark lesson about buffers.
II. Performance or learner outcomes
Students will be able to:
·
Identify what a
buffer does to a solution
·
Practice safety
during laboratory practices
·
Make valid
conclusions based on experimental results
·
Exemplify the
need for buffers in the ecosystem
III.
Resources, materials and supplies needed
Engagement:
1 beaker with water
pH
meter (with computer i.e. Vernier type)
Explorations: 30 Goggles
6 pH meters (with
Vernier program if possible)
30 plastic pipettes
24 600 ml beakers
A bottle of buffer
7
1 L 0.1 M HCl
1 L 0.1 M NaOH
Explanation: Have a source to connect a computer to a screen for students to
Be able to look at
tutorial
Elaboration: Have a sample of seawater in a 600 ml beaker
IV.
Supplementary materials, handouts.
Handout: What did I learn today?
Five-E Organization
Teacher
Does Probing Questions Student
Does
|
Engage: Learning Experience(s) Hydrogen and Hydroxide
ions are very reactive and changes in their concentrations can drastically
affect the proteins and other molecules of a cell. Our cells need to live at
a pH of about 7.4 in order to survive. Have a beaker w/ DI water
and squeeze 3 limes in it. Measure the pH. |
Critical questions that
will establish prior knowledge and create a need to know How does our body deal
with the amounts of acidity that we ingest? If the pH needs to be
maintained at around 7, how is it that our body still functions normally
after eating a lime and pickles? |
Expected Student Responses/Misconceptions The body contains chemical
buffers that help counteract the drastic changes in pH to control and keep pH
at a certain level. |
|
Explore: Learning Experience(s) Divide the classroom in
groups of 5 people. Each group will be in
charge of measuring pH of a solution that contains a buffer vs. a solution
that doesn’t contain a buffer. Remind them to wear
goggles at all times. Directions:
(How buffers work will be
explained in the consecutive benchmark lesson) |
Critical questions that
will allow you to decide whether students understand or are able to carry out
the assigned task (formative) What could possibly be
different between both solutions if they both have an initial pH of 7? |
Expected Student Responses/Misconceptions The
solution that doesn’t change pH as much with time has something else that helps it keeps its
pH |
|
Explain: Learning Experience(s) Have a group come up to
board and graph the lines that represent the two beakers to which acid was
added. Have a group come up to
board and graph the lines that represent the two beakers to which base was
added. At end of this section,
show the tutorial by Norton to further explain what buffers do. |
Critical questions that
will allow you to help students clarify their understanding and introduce
information related to concepts to be learned What
was our standard pH of water? What does this mean? Where
should that line for our standard solution go and how should it look like? What
happened when we added acid to beaker A1 (no buffer) and why? How
about when we added acid to beaker A2 (standard + buffer)? What could possibly be
different between both solutions if they both have an initial pH of 7? What
happened to the graph (of the weird behaved liquid) after some time? Why do
you think this happened? Ask
same questions for base addition. |
Expected Student Responses/Misconceptions It
is about 7. This means that there is an equal amount of hydrogen and
hydroxide ions. The
line for the standard solution is at y = 7 and should be a horizontal line. With
no buffer, the pH for the solution dropped dramatically The
pH did not drop as much compared to the one that didn’t have the buffer There
is something in the beaker that makes the solution counteract with the
addition of acid (or base) After
a while, the solution with the buffer dropped because it fell outside its
buffering capacity. |
|
Extend / Elaborate: Learning Experience(s) Have 2 beakers of fresh
water and sea water, respectively, and drop acid on both to see how the pH
changes (exemplifying the presence of buffers in seawater). Also, mention that lakes
in Our blood also contains
buffers for the change in pH i.e. when we exercise, pH drops but buffers
raise it (carbonic acid/bicarbonate buffer system) |
Critical questions that
will allow you to decide whether students can extend conceptual connections
in new situations Why is maintaining
pH important in seawater, in a lake, and in the blood stream? What would happen if our
blood did not have any buffering capacity? How about a lake or the sea? |
Expected Student Responses/Misconceptions Maintaining
a pH is important because organisms can only function at a certain pH. For
examples, certain enzymes will degrade in a strong acidic environment. Proteins
are also affected by a strong acidic environment. If we didn’t have a
buffering system in our blood or water reservoirs, any change in acidity or
basicity will dramatically alter the life of organisms living at that area
and would die. |
|
Evaluate: Lesson Objective(s) Learned (WRAP ≠UP
at end) -> Summarize Pass
out a quick sheet for students to answer. |
Critical questions that
will allow you to decide whether students understood main lesson objectives What is a buffer? What would happen if you
drop acid to a beaker that contains a buffer vs. a beaker that doesn’t
contain a buffer and why? Why is it important in the
ecosystem to have buffers in lakes and in the sea? |
Expected Student Responses/Misconceptions A
buffer is a solution that can counteract any fluctuations of acid and base to
keep a constant pH. The beaker that contains
the buffer will show almost no change in pH because the buffer that is
present helps counteract the sudden addition of acid. Organisms need to keep
homeostasis… an equilibrium in their environment and
buffers help organisms counteract any external fluctuations in acids or
bases. |
WHAT DID I LEARN TODAY?
What is a
buffer?
What would
happen if you drop acid to a beaker that contains a buffer vs. a beaker that
doesn’t contain a buffer and why?
Why is it
important in the ecosystem to have buffers in lakes and in the sea?