Yakima WATERS Mini Lesson
Water Chemistry, Photosynthesis, and Metabolism
Targets and Assessment
WA Science Standards Addressed:
 9-12 INQB Investigate
 9-11 ES2D
 9-11 LS1A
 9-11 LS2A
Lesson Parameters
Content Area: Biology
Overview: Observe changes in water chemistry due to
carbon dioxide acidification and photosynthetic oxygen
production.
Grade Level: 10
Assessments:
 Rubric
Suggested Time: 2 50 minute class periods
Special Materials:
 Bromothymol blue, Elodea plant
Learning Outcomes:
Knowledge: Students should be able to describe the relationship, as well as some similarities and
differences between animals and plants. Students should be able predict how pH indicators work.
Students should also be able to explain how pH, carbon dioxide, water, and photosynthesis relate to
one another. Students should be able to relate the factors of the lab to their watershed.
Skill: Experimental design, indicators, and observation.
Science Concept Background:
BTB is a pH indicator. Carbon dioxide will react with water to form a weak acid, causing BTB to change
colors, becoming green to yellow. Adding an aquatic plant to the acidified water should result in a
change in pH over time.
Materials:
Bromothymol blue 2 Containers (such as beakers) per group straws
Water
Elodea plant
Droppers
Procedure:
1)
Fill two beakers with tap water.
2)
Add BTB to both containers with an eye dropper until the water becomes blue
3)
Using a straw, blow bubbles in to the water until it changes color
4)
Students should note the change in color and be able to describe why this change took place
5)
Students should be able to design an experiment using the elodea plant and indicator based on
a hypothesis they form about photosynthesis, BTB, carbon dioxide, and oxygen.
6)
The lab experiment should be stored overnight and any observed changes the following day
should be recorded.
Key questions:
1)
Why did the Bromothymol blue change the color of the water?
2)
Why did the color of the solution change when you blew bubbles in it?
3)
Why did the color change again in the presence of the elodea plant?
4)
What is our relationship (animals) with plants? Why are we interdependent?
5)
What other dependency to we as animals have on plants?
6)
How do the lab results relate to watershed management?
7)
What other experiments can be devised using BTB?
Teaching Tips:
Students should design their own experiments. Some direction may be required to assist students in
experimental designs.
BTB, CO2, O2, photosynthesis, and water
Teacher Name: Mr. Lester
CATEGORY
Experimental
Hypothesis
4
3
2
1
Hypothesized
relationship
between the
variables and the
predicted results
is clear and
reasonable based
on what has been
studied.
Hypothesized
relationship between
the variables and the
predicted results is
reasonable based on
general knowledge and
observations.
Hypothesized
relationship between
the variables and the
predicted results has
been stated, but
appears to be based
on flawed logic.
No hypothesis
has been stated.
Experimental
Design
Experimental
design is a wellconstructed test of
the stated
hypothesis.
Experimental design is
adequate to test the
hypothesis, but leaves
some unanswered
questions.
Experimental design
is relevant to the
hypothesis, but is not
a complete test.
Experimental
design is not
relevant to the
hypothesis.
Conclusion
Conclusion
includes whether
the findings
supported the
hypothesis,
possible sources
of error, and what
was learned from
the experiment.
Conclusion includes
whether the findings
supported the
hypothesis and what
was learned from the
experiment.
Conclusion includes
what was learned
from the experiment.
No conclusion
was included in
the report OR
shows little effort
and reflection.
Scientific
Concepts
Answers illustrate
an accurate and
thorough
understanding of
scientific concepts
underlying the lab.
Answers illustrate an
accurate understanding
of most scientific
concepts underlying the
lab.
Answers illustrate a
limited understanding
of scientific concepts
underlying the lab.
Answers
illustrate
inaccurate
understanding of
scientific
concepts
underlying the
lab.
Author: Jack Lester, Yakima WATERS Project, CWU, Fall 2009