BIOLOGY
DEMONSTRATING EFFECT OF DIFFERENT SALT CONCENTRATIOS ON OSMOSIS WITHIN LIVING CELLS
To investigate the effect of concentration of sugar/salt solution on the mass of the plant tissue.
GRADE 9
TOPIC: PASSAGE OF MOLECULES INTO AND OUT OF CELLS
Acitvity: 9.B.1
1. LESSON INFORMATION
TIME DURATION: 180 MINUTES
1.1.
TARGET
GRADES
GRADE 9
√
GRADE 11
GRADE 10
GRADE 12
HANDS-ON
1.2.
√
SOFTWARE-BASED
ACTIVITY TYPE
COLLABORATIVE
1.3.
1.4.
ACTIVITY
SUMMARY
CROSS-CUTTING
DISCIPLINES
In this activity, participants will learn about the process of osmosis and how it is
affected by changing solute concentration of the tissue/cell environment using
materials, such as potatoes, sugar, and salt. Have you ever wondered how plants take
up water from the soil? Water uptake in plants is quite complex and involves a
process called osmosis. Osmosis makes the water from the soil move into the roots of
the plant. But what drives the water from the soil into the plant cells? In this activity,
students will do an experiment with potatoes to find out! They will make observations
and record data for further conclusion. Students will be carrying out an investigation,
constructing explanations, organizing and analyzing data and interpreting it.
PHYSICS
√
BIOLOGY
√
ENGINEERING
CHEMISTRY
√
MATHEMATICS
√
ARCHITECTURE
ENVIRONMENTAL
SCIENCE
ROBOTICS
ARTS
√
FOOD SCIENCES
√
SPACE SCIENCE
√
ICT
√
1.5.
STEM BASED
STUDENT
LEARNING
OUTCOMES
(SLOs)
Biology
 Explain the process of Osmosis and its effect on the living tissue.
 Relate plant cell structure with osmosis explanation.
 Interpret the data with real-life processes and draw conclusions.
Cross-cutting disciplines:

<<please identify the
most appropriate
ones from Section
1.7 below>>


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
21ST CENTURY
LEARNING
SKILLS
1.6.
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
Physics
o Understand the Cause i.e., changing solution concentration and its
Effect i.e., turgidity and flaccidity of plant tissue.
o Understanding how the structure of plant cells allows osmosis to
occur.
Food Science
o Students will be using potatoes to demonstrate osmosis in living
cells.
Engineering practices
o Students will be planning and carrying out an investigation,
constructing explanations. Data organization by measuring change in
length, analysis by tabulating data, and interpretation.
Math
o Students will be using metric ruler to measure length and interpret
through a line graph.
Chemistry
o Students will be preparing solutions of different molarities.

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

Critical thinking
Communication skills
Creativity
Problem solving
Perseverance
Collaboration
Technology skills and digital
literacy
Media literacy
Global awareness
Self-direction
Social skills
Literacy skills
Civic literacy
Social responsibility
Innovation skills
Thinking skills
Environmental Awareness
1.7. K-12 SCIENCE EDUCATION FRAMEWORK COMPONENTS
Reference: https://nap.nationalacademies.org/catalog/13165/a-framework-for-k-12-science-education-practicescrosscutting-concepts
1.
Scientific and Engineering Practices
a)
Asking questions (for science) and defining
problems (for engineering)
2.
Cross-cutting areas
a)
Patterns
b) Developing and using models
b) Cause and effect: Mechanism and
explanation
c)
c)
Planning and carrying out investigation
Scale, proportion, and quantity
d) Analyzing and interpreting data
d) Systems and system models
e)
Using mathematics and computational thinking
e)
f)
Constructing explanations (for science) and
designing solutions (for engineering)
Energy and matter: Flows, cycles, and
conservation
f)
Structure and function
Engaging in argument from evidence
g)
Stability and change
g)
h) Obtaining, evaluating, and communicating
information
2
3.
Disciplinary Core Ideas
Physical Sciences
a. Matter and its interactions
b. Motion and stability: Forces and
interactions
c. Energy
d. Waves and their applications in
technologies for information transfer
Life Sciences
a. From molecules to organisms: Structures
and processes
b. Ecosystems: Interactions, energy, and
dynamics
c. Heredity: Inheritance and variation of
traits
d. Biological evolution: Unity and
diversity
Earth and Space Sciences
a. Earth’s place in the universe
b. Earth’s systems
c. Earth and human activity
Engineering, Technology, and Applications of STEM in
society
a. Engineering design
b. Links among engineering, technology,
science, and society
3
BIOLOGY
DEMONSTRATING EFFECT OF DIFFERENT SALT CONCENTRATIOS ON OSMOSIS WITHIN LIVING CELLS
To investigate the effect of concentration of sugar/salt solution on the mass of the plant tissue.
GRADE 9
TOPIC: PASSAGE OF MOLECULES INTO AND OUT OF CELLS
Measurements and Calculations
Acitvity: 9.B.1
1. TEACHERS RESOURCES





BACKGROUND
INFORMATION

All cells are surrounded by a cell membrane which is partially permeable
Water can move in and out of cells by osmosis
Osmosis is the diffusion of water molecules from a dilute solution (high concentration of
water) to a more concentrated solution (low concentration of water) across a partially
permeable membrane
In doing this, water is moving down its concentration gradient
The cell membrane is partially permeable which means it allows small molecules (like water)
through but not larger molecules (like solute molecules)
Osmosis and the partially permeable membrane
It can get a little confusing to talk about the 'concentration of water' when we also talk
about solutions being ‘concentrated’ (having a lot of solute in them), so instead we can say
that a dilute solution has a high water potential (the right-hand side of the diagram below)
and a concentrated solution has a low water potential (the left-hand side of the diagram
below):
How osmosis works




Osmosis in Animal Tissues
Animal cells also lose and gain water because of osmosis.
As animal cells do not have a supporting cell wall, the results on the cell are more severe.
If an animal cell is placed into a strong sugar solution (with a lower water potential than the
cell), it will lose water by osmosis and become crenated (shriveled up)
If an animal cell is placed into distilled water (with a higher water potential than the cell), it
will gain water by osmosis and, as it has no cell wall to create turgor pressure, will continue to
do so until the cell membrane is stretched too far, and it bursts.
Effect of osmosis on animal cells
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
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

Osmosis in Plant Cells
If a plant cell is placed in pure water or a dilute solution, water will enter the plant cell
through its partially permeable cell surface membrane by osmosis, as the pure water or
dilute solution has a higher water potential than the plant cell.
As water enters the vacuole of the plant cell, the volume of the plant cell increases.
The expanding protoplast (living part of the cell inside the cell wall) pushes against the cell
wall and pressure builds up inside the cell – the inelastic cell wall prevents the cell from
bursting.
The pressure created by the cell wall also stops too much water entering and this also helps
to prevent the cell from bursting.
When a plant cell is fully inflated with water and has become rigid and firm, it is described as
fully turgid.
This turgidity is important for plants as the effect of all the cells in a plant being firm is to
provide support and strength for the plant – making the plant stand upright with its leaves
held out to catch sunlight.
If plants do not receive enough water the cells cannot remain rigid and firm (turgid) and the
plant wilts
Osmosis of water into a plant cell
If a plant cell is placed in a solution with a lower water potential than the plant cell (such as a
concentrated sucrose solution), water will leave the plant cell through its partially permeable
cell surface membrane by osmosis.
As water leaves the vacuole of the plant cell, the volume of the plant cell decreases.
The protoplast gradually shrinks and no longer exerts pressure on the cell wall.
As the protoplast continues to shrink, it begins to pull away from the cell wall.
This process is known as plasmolysis – the plant cell is plasmolyzed.
5
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


IMPORTANT
DEFINITIONS







Plasmolysis of a plant cell that has been placed in a solution with a lower water potential
than the cell itself
Flaccid – soft, limp, without firmness. In biology, flaccid indicates the state of cells where the
structure is weakened due to lack of fluid within the cell.
Hypertonic – 1. a solution with higher osmotic pressure. 2. excessive muscle tension. (Hyper
= over, above, e.g. hyperactive, hyperglycaemia).
Hypotonic – 1. a solution with a lower osmotic pressure than a comparison solution. 2.
abnormally low muscle tension. (Hypo = under, low, e.g. hypothermia).
Isotonic – two solutions with equal osmotic pressure or muscles with equal tension. (Iso- =
equal, e.g. isomer).
Plamolyzed - past participle of the verb ‘plasmolyse’ (British English) or ‘plasmolyze’ (U.S
English) – to cause a cell to undergo plasmolysis. Plasmolysis – the protoplasm of a plant or
bacteria cell shrinks and separates from the cell wall due to exosmosis.
Regulate – to control or regulate the speed of something. (Reg- = to rule or direct. Examples;
regimen, regent, regal, region).
Semipermeable – describes a material that allows only some substances through. (Semi- half or partial. E.g. Semipermeable, semi-automatic, semi-final).
Solvent – a liquid that dissolves other substances.
Toxic – poison.
Turgid – swollen or bloated.
Molar concentration
concentration measured by the number of moles of solute per liter of solution
1.1. STEP-BY-STEP INSTRUCTIONS
COMPONENTS REQUIRED
Each group needs:
CHECKING
DISTANCES
FOR
ACCURACY




HANDS-ON MATERIALS







Distilled water
Measuring cylinder
Several potatoes
Apple corer or cork borer. Alternatively, you can use a cutting board
and knife.
Sucrose/Glucose
Scale with gram measurements
Boiling tubes/beakers 100ml
Spoon
Ruler
Paper
Pen/Pencil
6
DIGITAL/COLLABORATIVE
TOOLS







Timer
Paper towels
Graphing paper
Knife
Wax pencil
0.2, 0.4, 0.6, 0.8 and 1.0 molar sucrose solution
Potato peelers

N/A
STEPS TO FOLLOW
STEPS
IMAGES
Divide the class into groups of 4. Ensure the
following for the investigation:
 You should measure both the mass and
the length of each potato cylinder
before and after it has been submerged
in solution - these measurements are
your dependent variables from which
you will calculate the percentage
change in mass and length.
Variables
 Independent Variable - The
concentration of sugar solution.
 Dependent Variable The mass of plant tissue at the end.
 Control Variables - Volume of plant
tissue. Surface area of plant tissue.
Length of time the plant tissue is left in
solution. Temperature of the solution.
1. Preparation
 Prepare the different sugar solutions.
 Create labels for boiling tubes/beakers.
 Add the sugar solutions to the respective
boiling tube/beaker. Do not fill. Leave
some space to account for adding potato
strip in it.
 Draw 2 tables in which you can enter the
starting measurements (length and
mass) and end measurements of each
potato strip for every sugar
concentration (0.2, 0.4, 0.6, 0.8 and 1.0)
 Prepare potato cores. Carefully push the
corer/borer all the way through the
potato, and remove the core carefully so
the potato piece stays intact. The potato
pieces should be at least one-half inch
thick and two inches long. (Optional:
Ideally you should prepare 18 matching
cores or strips so you can test three
pieces in each solution to compare the
results thoroughly.)
7
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

Use a knife to carefully remove any
potato skin from your cores, and rinse
the cores quickly with water.
Use a ruler to ensure each potato piece
is the same size. Carefully use a knife to
trim any pieces as needed.
Measure the length and mass of each
potato strip and write the information in
the table.

2. Pour distilled water in a beaker and label it
as distilled water.

3. Put one potato strip (or three) into each of
the boiling tubes/beakers. While you do that
feel the potato strips with your fingers and
try to flex them a little bit. How do they feel?
Are they easy to bend?

4. Start your timer for 30 minutes. Let the
potato strips sit in the different solutions for
the whole time.
5. After 30 minutes inspect the potato strips
inside the solutions. Do you see any changes?
6. Take the potato strip(s) out of the boiling
tubes/beakers (one beaker at a time) and
place on a paper towel. While doing that feel
the potato pieces again and try to bend them
slightly. How do they feel? Are they easier or
more difficult to bend than before?



7. Use the ruler to measure the exact length
and of each of the potato strips, and write
the results in your table. What do you notice
about the potato strip
measurements? Weigh these pieces and
record their weights in the table.
 How did the feeling of the strips compare
based on what solution they were in?
Why do you think this is?
 Compare the results in your table. How
did the length and weight of the potato
strips change in each beaker/boiling
tube?
8

8. Make a graph of your results with the
sugar concentration on the horizontal axis
and the potato strip length or weight after
soaking on the vertical axis. Draw two lines to
make your graph. For the first, connect each
of the data points you found. For the second,
draw a horizontal line starting at the point on
the vertical axis that shows the original length
of your potato strip.
 Based on your graph can you find a sugar
concentration at which the potato strip
length should not change at all?
9
1.2. LESSON PLAN
CLASSROOM ACTIVITY
180 MINUTES
STEM lessons are best taught using the 5E Model which places students at the center of learning.
The five phases of the 5E Model are: Engaging prior knowledge, explain new concepts, explore new concepts, elaborate
or implement the knowledge acquired in new unseen scenarios, and evaluate the student’s understanding of concepts
taught through formative or summative assessments. This way, it encourages all students to explore, construct
understanding of scientific concepts, and relate those understandings to phenomena or engineering problems.
The teacher will follow the Lesson Plan given below for this STEM project in classroom.
5E LEARNING
SEQUENCES
ACTIVITIES
TIME
Begin by asking this question:

ENGAGE

If you were stranded on a desert island and had nothing to drink, what would you
do?
It would not be a good idea to drink salty ocean water. Knowing that water moves
in and out of the cells, why would you need fresh drinking water?
(Your body cells need water to perform their activities and if a cell’s environment
was too salty, the cell would lose too much water through osmosis)
How does the size of a cell change when water enters or leaves it?
(A cell can swell when water enters & shrivel when water leaves)
 Explain they will be divided into groups of 4 each.
 Explain the procedure of the investigation.
 Explain to them they will:
--Observe the texture and color of each of the potato slices and record their
observations in their notebooks.
--Predict what will happen in each of the beakers and write it in their notebooks.
 Watch the following video:
https://www.youtube.com/watch?v=GQAVND5rtcw
EXPLAIN
Controlled Variable
Why
How
Duration of potatoes in
sugar solutions.
If the timing was inconsistent then
results would become unreliable and
incomparable due to the false results. If
some potatoes were left in the solution
for longer then more osmosis would
occur and if potatoes were left for a
shorter time, less osmosis would occur.
The timing of potatoes in the
sugar solution can be kept
consistent with the use of a
stopwatch and leaving the
potato cubes in the solution
for only 20 minutes.
Size
The dimensions and mass had to be
consistent among all potatoes or the SA:
Vol ratio would be different resulting in
faster rates of osmosis, providing
inaccurate data.
The dimensions and mass
were kept similar by using a
ruler to adjust the
dimensions of the potato
cubes and weighing them all
to ensure a similar mass.
Volume of solution
If the volume of sugar solution is
different in the four beakers, then there
will be more/less water to transport by
osmosis. The potatoes would then
gain/lose mass creating a random error
and resulting in data that differs from
the true answer.
The volume of sugar solution
can be controlled by using a
measuring cylinder to
maintain accurate results.
The solution should be
measured on a stable, flat
bench.
10
minutes
20
minutes
Type of potato
If the potatoes are different types, then
the salt will be varied in the potatoes. If
the salt level is different then it will
affect the rate of osmosis creating a
random error in the data.
The same variety of potatoes
should be used for all testing
to have the same salt level,
keeping the data consistent.
1.

EXPLORE &
ELABORATE





1.
EVALUATE
2.
Elaborate on practical implementation of this project as per instructions given
in.
2. Let each group assemble their apparatus and take their readings.
3. Ask students to record their results in a table.
4. Ask them to interpret their results using graphical representation.
5. Discussion Questions while waiting for the 30 min of the investigation:
What do you know about osmosis? (Encourage students to raise their hands and
share ideas)
How is osmosis different than diffusion?
(Diffusion is the movement of particles from where they are more concentrated to
where they are less concentrated.)
Will osmosis take place between the potato slice and the sugar solutions, the
water, or all of them? What do you think?
What other experiments or places do you think osmosis occurs? (when a plant
wilts, when you eat something salty, etc.)
Remove the potato slices and observe the texture and color of each slice.
Teacher will use questions mentioned in Section 1.3 below for formative
assessment of students.
Teacher will evaluate student’s understanding of the concept by applying the
summative assessment questions in Section 1.3 after the completion of the
project, or in monthly, midterm or final exams.
90
minutes
60
minutes
1.3. FORMATIVE AND SUMMATIVE ASSESSMENTS
Table 1: Formative Assessments
FORMATIVE ASSESSMENT
QUESTIONS
Questions that teachers may
ask students
1.
1.
2.
3.
4.
Do you notice any changes?
Changes in length, mass and flaccidity or turgidity.
What do you notice about the potato strip measurements?
Mention the increase or decrease.
What are the independent and dependent variables in this experiment?
How does Change in Mass (%) change with Sucrose Concentration (Molarity)?
Mention the increase or decrease.
Which substance moved across the cellular membrane in this activity? What is
the specific name of the movement in terms of this substance?
Water - Osmosis
Table 2: Summative Assessments
These questions will be added on LMS and evaluations will be conducted online.
Criterion A: Knowing and Understanding
Fill in the blanks using the words from the word bank below. Each word will be used
once
SUMMATIVE EVALUATION
11
Evaluation items to test the
knowledge of the student
acquired after this project
based activity is completed.
These items can be used in
monthly, midterm or final
exams.
Cells are surrounded by a ____________________ __________________ membrane,
through which
they exchange materials with their ____________________. As a result of
__________________,
substances tend to move through the membrane from areas of _________
concentration to areas of _______
concentration. The diffusion of water is known as ______________.
The movement of water through a cell membrane is determined by the relative
amounts of dissolved
materials inside and _____________ of the cell. Dissolved materials are called
___________, while the liquid
the material is dissolved in is called the ______________. When the cell contains a
higher concentration of
dissolved materials than the external environment, water will move ________ the cell,
increasing the cell’s
mass. The external environment is ___________________ to the cell. When the
external environment
contains a higher ___________________ of dissolved materials than the cell,
__________ will move ______
of the cell, resulting in a ________________ in the cell’s mass. Now, the external
environment is
___________________ to the cell. When the concentration of dissolved materials is
the same on both sides
of the cell _________________, there will be no net osmosis and no change in the
________ of the cell. This
condition is called _______________.
Cells are surrounded by a ___selectively__________ _permeable__________
membrane, through
which they exchange materials with their _surroundings/environment_____________.
As a result of
__diffusion____, substances tend to move through the membrane from areas of
__high____ concentration to
areas of ___low____ concentration. The diffusion of water is known as
_osmosis_____________.
The movement of water through a cell membrane is determined by the relative
amounts of dissolved
materials inside and __outside_______ of the cell. Dissolved materials are called
__solutes____, while the
liquid the material is dissolved in is called the _solvent____. When the cell contains a
higher concentration of
dissolved materials than the external environment, water will move _into____ the
cell, increasing the cell’s
mass. The external environment is ___hypotonic________ to the cell. When the
external environment
contains a higher _concentration___________ of dissolved materials than the cell,
_water___ will move _out__
of the cell, resulting in a ___decrease______in the cell’s mass. Now, the external
environment is
12
___hypertonic____ to the cell. When the concentration of dissolved materials is the
same on both sides of the
cell ___membrane_______, there will be no net osmosis and no change in the
__mass___ of the cell. In this
condition, the cell is __isotonic_____________ to its surroundings.
Criterion B: Inquiring and Designing
Q. Which solution is closest to being isotonic with respect to a potato cell? Which
solutions were hypertonic/hypotonic? How do you know?
Depends on results.
Criterion C: Processing and Evaluating
1.
2.
3.
In this experiment, why was it important that the potato chunks were
approximately the same size?
Into which of the potato chunks did water flow? From which of the potato
chunks did water flow? How can you tell?
Which solutions (if any) were hypertonic, isotonic, or hypotonic? Explain how
you know.
Criterion D: Reflecting on the Impacts
Let the students answer from their own:
Q. Using the principles illustrated with these data, explain why you can’t drink
seawater when lost at sea.
13
BIOLOGY
DEMONSTRATING EFFECT OF DIFFERENT SALT CONCENTRATIOS ON OSMOSIS WITHIN LIVING CELLS
To investigate the effect of concentration of sugar/salt solution on the mass of the plant tissue.
GRADE 9
Measurements and Calculations
Acitvity: 9.B.1
TOPIC: PASSAGE OF MOLECULES INTO AND OUT OF CELLS
2. STUDENTS RESOURCES
OSMOSIS HANDOUT
AFTER THE INVESTIGATION ATTEMPT THE WORKSHEET BELOW:
15