Diffusion Confusion Solved!
Diffusion & Osmosis and Cells
10th grade biology
Beth Stewart
EDTEP 587
Subject area description:
This topic will be taught to students in 10th grade biology. As the school has a
completely integrated population of students, this unit will be taught to students of a variety of
abilities, ranging from highly gifted students to students who are learning challenged. A small
percentage (~3%) of the students will be English language learners.
Some prerequisite skills and knowledge are needed for this unit, including basic skills in
designing and analyzing experiments. In order to design their own procedures for some of the
investigations, students will need to have some familiarity with creating hypotheses, designing
experiments, and identifying variables. They will also need to have elementary observational
skills. As always, these skills should be continually practiced throughout the school year. They
will have been introduced in a previous unit. Additionally, students will have been introduced to
the basic idea of cells during a previous unit. Previous topics in the year include energy and
nutrient transfer in ecosystems (and homeostasis), populations biology, and body systems. Later
topics may include DNA function, genetic inheritance, development, evolution, and ecology.
Essential questions:
Why can’t you dispose of chemicals too near to a lake, river, or ocean (for example, when you
are camping)? Or wash your car where the suds will get into the water? What happens to these
chemicals after they get into the water? How do they end up contaminating so many organisms
in such a large area?
These are questions that are relevant to students’ lives. Many household products must be
disposed of in careful ways to prevent them from contaminating our waterways. Students need
to understand the catastrophic effect that can be caused by contamination by these chemicals. In
order to answer this question, students will need to examine how molecules (and therefore, these
chemicals) can spread throughout the water through the process of diffusion, effectively
contaminating a much larger area than the area where the chemical was dumped. They will also
examine how factors like temperature can affect this process. Students will also need to know
how molecules can get inside of organisms, specifically inside of cells. Therefore, students will
need to learn how molecules can and cannot pass through membranes.
Why are cells so incredibly tiny?
This is the question students will be answering in their inquiry investigation. Students will learn
that cells are small in order to facilitate quick nutrient and energy exchange. They can connect
this idea back to the water contamination question by realizing that chemicals will also diffuse
throughout a cell quickly based on its small size. Therefore, students will be able to see how
small size is both integral to the cell’s survival and damaging in other respects.
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Diffusion Unit
Learning goals and objectives:
1. Students will develop abilities necessary to do scientific inquiry. (EALR 2.1)
1.1. Students will identify independent and dependent variables in an experimental set-up.
1.2. Students will design and conduct scientific investigations (benchmark 2.1.2).
1.3. Students will interpret scientific results and make conclusions based on evidence
(benchmark 2.1.3).
1.4. Students will create models to illustrate the behavior of processes and objects
(benchmark 2.1.4).
1.5. Students will interpret graphs to recognize experimental conditions.
2. Students will understand and describe the molecular basis of diffusion.
2.1. Students will describe how collisions between constantly and randomly moving particles
lead to the phenomenon of diffusion (Atlas CF).
2.2. Students will know that gaseous, liquid, and solid particles can diffuse.
2.3. Students will understand the meaning of solution concentration.
2.4. Students will know that molecules diffuse from high concentration to low concentration.
2.5. Students will explain how environmental conditions (size of concentration gradient,
temperature, and pressure) can alter the rate of diffusion (Atlas CF).
2.6. Students will analyze how diffusion and osmosis are affected by a membrane.
3. Students will understand how cells sustain life by obtaining and eliminating matter in a
regulated fashion (EALR benchmark 1.3.7).
3.1. Students will explain how cellular membranes regulate what enters and leaves a cell
based on size, shape, and charge of molecules (Atlas CF).
3.2. Students will describe, explain, and predict the behavior of cells and molecules in
hypotonic, hypertonic, and isotonic solutions.
3.3. Students will understand and explain the importance and consequences of surface area to
volume ratios in cells.
3.4. Students will hypothesize about the functions of various cell types in relation to cell
shape.
3.5. Students will analyze the reasons for and types of adaptations cells make to cope with
their environments (related to benchmark 1.3.8).
4. Students will learn to effectively communicate scientific understanding to others (EALR
benchmark 2.1.5).
4.1. Students will illustrate conclusions using visual representations.
4.2. Students will use appropriate language in written expression.
4.3. Students will justify conclusions orally.
4.4. Students will organize evidence so that others can understand their conclusions.
5. Students will learn that effective group collaboration is integral to scientific
investigation.
5.1. Students will listen to other group members’ ideas and concerns.
5.2. Students will actively participate in group activities.
5.3. Students will analyze the advantages and disadvantages of doing inquiry in a group.
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Diffusion Unit
Unit matrix
As students will be working in groups each day, 2 objectives will be part of each day’s lesson. They are listed
below.
5.1 Students will listen to other group members’ ideas and concerns.
5.2 Students will actively participate in group activities.
These objectives will be assessed through informal teacher observation and peer and self assessment.
WEEK ONE: Throughout this week, students will be working toward PHASE I of Inquiry: Hooking students and
building a knowledge base. The concepts they learn this week will serve as needed background
information for the guided inquiry next week.
DAY 1: (50 minutes) Introduction to Diffusion
1. What students are doing
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
4. Evidence of understanding
5. Resources
Stewart
Eliciting ideas: Students will work in groups to illustrate their preliminary
understanding of the essential question (picture of chemical pathway). Groups will
then present ideas to the class. Class discussion: Students will observe a demo of
dye in liquid and discuss, “What do you think is happening here?” “Why is the dye
spreading out?” Next, students will make observations about an opened perfume
bottle and how long it takes each row to smell the perfume (collect data on board).
Pose the questions: “How is this like the dye demo? What do you think is
happening here?” Students will create a KWL chart in their journals about these
questions and then share their work with the class to create a collective KWL chart.
Review the concept of molecules and Introduce the concept of concentration. If
students have not mentioned it, I will point out that the dye and perfume molecules
move from high to low concentration.
2.3 Students will understand the meaning of solution concentration.
2.4 Students will know that molecules diffuse from high concentration to low
concentration.
I want to start this unit with a scenario that is relevant to students’ lives. Therefore,
I begin by posing the first essential question. Diffusion is a hard concept to
visualize as it is a molecular phenomenon and I want to bring a common
consequence of diffusion to my students’ attention before addressing the molecular
nature. I want to start with eliciting their ideas for 2 main purposes. First, I want
to get them interested in a new unit and foster a feeling that they have experiences
to contribute and second, I want to find out what they already know from their
previous schooling and/or extracurricular experiences. I chose to use demos along
with eliciting their ideas so that they would have a visual to stimulate their
thinking. Both demos are common things they would see in everyday life and I
think this will increase the likelihood that students will have ideas/interest about
what is happening. I chose to begin this unit with simple diffusion, not because it
is the easiest for students to conceptualize, but because diffusion is the driving
force behind everything else we will discuss in this unit. In order to fully
understand osmosis, diffusion through a membrane, and cellular size, behavior and
regulation, students will need to understand the role of simple diffusion in these
processes.
I will be examining the students’ KWL charts in their journals. Primarily I will be
looking for effort and any ideas that the students generated.
Dish of water, food coloring, perfume, butcher paper and markers
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Diffusion Unit
DAY 2: (75 minutes) Molecular basis of diffusion (with and without a membrane)
1. What students are doing
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
4. Evidence of understanding
5. Resources
Stewart
Students will reexamine the dye demo and be introduced to molecular collisions,
diffusion and equilibrium, and consider types of molecules that can diffuse (use
computer simulation at http://physioweb.med.uvm.edu/bodyfluids/membrane.htm).
Students will take notes in their journals and compare diffusion of gases, liquids,
and solids. Then students will model molecular collisions and diffusion with
people in a taped off square on the floor. Small group discussion: Groups will
reexamine their pictures from the previous day to see if they can apply what they
have learned about diffusion to the essential question. Students will share ideas
with the class. How do these chemical molecules get into cells living in the lake,
etc.? (Diffusion through a membrane) Students will observe the vanilla-flavoringin-a-balloon demo and make observations related to diffusion. “Does the
membrane stop diffusion?” Introduce the idea of the cell membrane and its main
purpose. Students will take notes in their journals. Groups will then model
diffusion through a membrane in an activity, Starch/iodine diffusion Part A.
Students will analyze how the presence of a membrane affects diffusion. They will
write the question, draw the set-up, and write observations, results, and conclusions
in their journals (including a drawing). Students will observe osmosis in the egg
demo and then analyze how osmosis relates to the activity they just completed.
(SAVE EGG) Group discussions: What factors might be able to alter our
diffusion/osmosis results? They will write their ideas in their journals. (Students
will test one idea tomorrow.)
2.1 Students will describe how collisions between constantly and randomly
moving particles lead to the phenomenon of diffusion (Atlas CF).
2.2 Students will know that gaseous, liquid, and solid particles can diffuse.
2.6 Students will analyze how diffusion and osmosis are affected by a membrane.
1.3 Students will interpret scientific results and make conclusions based on
evidence.
I am starting this lesson with an explanation of the molecular behavior of diffusion
without a membrane so that students can focus on the molecules before figuring
out how they relate to a membrane. I am using a computer simulation and a
student demo so that students can start to visualize the concept. Also, I think that
students become more involved when they can be part of the demos and get up out
of their seats. I want groups to return to their drawings from the previous day so
that they can apply what they have learned to the macroscopic effects highlighted
in the essential question. Once they understand diffusion without a membrane, I
will introduce diffusion through a membrane and the idea that cells have
membranes. I have chosen to only briefly discuss cell membranes at this point
because I want students to “see” how membranes can regulate by size from the lab
activity before I tell them. I also want them to “see” osmosis and wonder what is
happening before they get the detailed content. After all, students need to DO
science to LEARN science! I want this lab activity to be structured so that I am
sure students have the fundamental knowledge they will need for tomorrow’s
activity (Part B of the lab). Homework: finish conclusions in journal
Journal entries— students will be recording their conclusions (including a drawing)
about the lab activity.
Dish of water, food coloring, computer with projector, tape, vanilla balloon and
cardboard box, ingredients for starch/iodine lab, dialysis tubing, beakers, egg demo
(2 eggs, vinegar, Karo syrup, water, beakers), SAFETY: chemicals
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Diffusion Unit
DAY 3: (75 minutes) Environmental effects on diffusion (Structured Inquiry)
1. What students are doing
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
4. Evidence of understanding
5. Resources
Students will perform Starch/Iodine Part B: structured inquiry to test an
environmental effect on diffusion rate and osmosis (initial concentrations
(higher/lower), temperature, etc.). They will develop hypotheses (as groups),
modify experimental designs (I will give them a basic design and they will alter the
independent variable) and conduct the experiments. Students will analyze results
as a lab group and make conclusions. Students should document all steps in their
journals. They will organize their findings and conclusions on paper and present
them to the class so that each student learns the effects of each factor. Students
will be encouraged to ask questions of one another’s work. (SAVE SET-UPS)
2.5 Students will explain how environmental conditions (size of concentration
gradient, temperature, and pressure) can alter the rate of diffusion (Atlas CF).
1.1 Students will identify independent and dependent variables in an experimental
set-up.
1.2 Students will interpret scientific results and make conclusions based on
evidence.
Objectives related to presentation:
4.1 Students will illustrate conclusions using visual representations.
4.2 Students will justify conclusions orally.
4.3 Students will organize evidence so that others can understand their
conclusions.
Yesterday, students analyzed the basics of diffusion in action and came to some
conclusions about the relationship between membranes, solute movement, and
osmosis. Today, I want them to see another example which shows that diffusion is
indeed due to molecular action. Again, I want them to deduce the ideas from
experience and so have set up the learning activity as a structured inquiry. Part B
of the lab will also reinforce what they learned the previous day by building upon
students’ knowledge and skills. Additionally, by having the students present to
their peers, I can be sure that all students hear about each environmental change
and that the presenting group members have a solid understanding of the molecular
basis of diffusion. Students will also gain practice in communicating scientific
ideas with their peers, an authentic skill required of real scientists.
1. Student presentations (both visual and oral), 2. lab conclusions in their journals
Ingredients for starch/iodine lab, dialysis tubing, beakers, butcher paper, markers,
handouts of basic experimental design, SAFETY: chemicals
DAY 4: (50 minutes) Cell membranes and diffusion/osmosis
1. What students are doing
Stewart
Discussion of cell membranes: Students will examine a drawing of a cell
membrane and identify how it is similar to the dialysis tubing from the lab activity.
Students will use their dialysis bags or the egg demo as models for the behavior of
cells in varying concentrations of solution (ex. limp, turgid, normal). Students will
then examine pictures of red blood cells that have burst/shrunk. Next, students will
examine onion cells under a microscope as water enters the cells. They will write
an explanation of what is happening and why in their journals and then discuss
their ideas with the class. Finally, students will examine the ramifications of
regulation by size and obtaining nutrients. Students will justify why food must be
broken down into very small particles before it can get into cells. “What does this
mean for toxic chemicals getting into the cell (essential question)?” (only if they
are small enough—most are.) Students will also learn that cells can regulate by
charge and shape. Homework: Students will receive a handout of cell types of
varying shapes. At home, they will predict what environment each cell type might
be found in based on its unusual shape. Also, what is similar amongst all the cell
types? Different?
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Diffusion Unit
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
4. Evidence of understanding
5. Resources
3.1 Students will explain how cellular membranes regulate what enters and leaves
a cell based on size, shape, and charge of molecules (Atlas CF).
3.2 Students will describe, explain, and predict the behavior of cells and molecules
in hypotonic, hypertonic, and isotonic solutions.
3.4 Students will hypothesize about the functions of various cell types in relation
to cell shape.
At this point in the unit, students should have a fairly clear understanding of
diffusion and osmosis, but before they are able to do the guided inquiry next week
they need a bit more instruction about cells. Some of this lesson will be minilecture, but I will involve students in the instruction by continually referring back
to the starch/iodine activity they have been doing and also peppering the lesson
with visuals and mini-activities (onion cells, revisiting their dialysis bags). By
doing this, I hope to get students to shift their thinking from diffusion in a nonliving dialysis bag to diffusion in a living cell. During the inquiry next week, I
want them to be using their models to visualize cells, and have the implications of
SA and V for cells at the forefront of their minds. As usual, the activities serve to
keep the students interested and provide them with much needed visuals. Finally, I
am using their homework assignment to expose them to the idea that cells can have
very different shapes. I hope students will wonder why.
Journal entries—explanations of what is happening in the onion cell
Microscopes, onion cells, water droppers, water, pictures of red blood cells,
overhead of cell membrane, dialysis bags from previous day, egg demo, homework
pictures
WEEK 2:
DAY 5: (50 minutes) PHASE II of Inquiry: Crafting questions, hypotheses, predictions and initial models
1. What students are doing
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
Stewart
Using homework from the previous week, students will discuss some of their ideas
with the class. “How are these cells similar? Different? Why might this be?” As
a class, students will generate a list of questions they would like to answer (written
in journal) and then small groups will discuss which questions they could actually
test. “How do you know what is testable?” I will steer the class toward examining
size of the cell and pose the second essential question to them, “Why are cells so
incredibly tiny?” Again, students will work in small groups to generate ideas and
hypotheses (written in journal). In the large group, students will share ideas (I will
steer them toward the relationship between size and diffusion), discuss the
alternative hypotheses, and create an if-then prediction for the class. Students
will then be introduced to the model that we will use for the cell (agar cube with
BTB). Class discussion: Students will identify limitations and assumptions of the
proposed model. How can we use our model to test our hypothesis? Students will
spend the remainder of class time (if any) brainstorming about how they might
design the experiment. In their journals, students should record any questions they
have. Homework: Based on what their group has come up with, students should
identify one controlled variable, the independent variable, and the dependent
variable at home and bring them to class tomorrow. Additionally, they should
finish writing out their ideas for an experimental design.
1.4 Students will create models to illustrate the behavior of processes and objects
(benchmark 2.1.4).
1.1 Students will identify independent and dependent variables in an experimental
set-up.
Students may have difficulty with this part of the inquiry as they have had little
experience with talking about models. Therefore, I want to give them plenty of
small and large group discussion time to generate ideas and get used to the idea. I
will provide lots of help in the small groups as I feel students may easily become
lost and frustrated if they fall behind. Also, I want students to have some time to
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Diffusion Unit
4. Evidence of understanding
5. Resources
think about the experimental design at home before they are asked to completely
design and conduct their experiments.
Journal entries—students will have hypotheses, predictions, and questions recorded
in their journals. Also, I will be able to get a feel for how well the students
understand models from their comments and questions in large and small group
discussion (informal observation).
None needed
DAY 6: (75 minutes) PHASE III of Inquiry: Designing and conducting the investigation
1. What students are doing
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
4. Evidence of understanding
5. Resources
Students will start by listing any questions they have in their journals. Using their
ideas from the homework, students will work through the “Post-IT” activity as a
class to identify the independent and dependent variables and to fit them into
the prediction if not already there. Before deciding on what to measure, students
will be given one agar block and some vinegar solution. They will experiment
with what happens. Then students will return to the “Post-IT” activity and will
generate ideas about how they want to measure their variables (operationalize the
variables). The class will develop methods of measurement so that everyone is
consistent and reliable. Students will then work in groups to finish their
experimental designs and create a data table based on what the class decides to
measure. When ready, students will conduct their experiment and collect data. In
small groups, students should then critique their designs in light of their initial data
collection and revise and repeat if necessary.
1.2 Students will design and conduct scientific investigations (benchmark 2.1.2).
1.4 Students will create models to illustrate the behavior of processes and objects
(benchmark 2.1.4).
I want the students to learn to continually ask questions and to learn that questions
are just as good, or better, than answers. Therefore, I want to start each day of the
inquiry with writing questions in their journals. I have chosen to do the “Post-IT”
activity because I feel that it is a simplified, visual, and systematic way to work
through the complexities of experimental design. Part way through the “Post-IT”
activity, I want students do gain some experience with the experimental materials
so that they have an idea of what is possible to measure. After they have seen one
agar block and observed the diffusion of vinegar lead to a color change, I feel they
will be better able to figure out how to measure diffusion rate and size of cell (agar
block). From there, I have chosen to have students operationalize their variables.
Students are more likely to feel that they have ownership in their investigation if
they decide for themselves how to collect data. Additionally, I want groups to
have a chance to perform their experiments and revise the methods or data table if
necessary. I feel that it is important for students to struggle with these things in
order to best learn them.
Students will have their original and revised experimental designs in their journals.
Therefore, I will be able to compare the two to see what students have learned.
Tag boards for “Post-IT” activity, Post-Its, agar with BTB, vinegar solution, plastic
knives, paper plates, beakers, stopwatches, balance, SAFETY: chemicals and
knives
DAY 7: (75 minutes) PHASE IV of Inquiry: Analyzing data and representing it as evidence
PHASE V of Inquiry: Reconsidering the model, coordinating evidence and theory
1. What students are doing
Stewart
Students will start by writing questions they have in their journals. Then students
will work in small groups to analyze the findings from the investigation. Students
will then enter their data into a table produced on the front board to produce a class
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Diffusion Unit
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
4. Evidence of understanding
5. Resources
data set for discussion. In the large group, students will discuss what is easy to
decipher from the table and what is difficult. Students will consider calculations
that might help their analysis and develop other ways to represent their data. Mini
discussion on graphs—students should examine several different kinds of graphs
and generalize about what type of data works best with each type. Students will
then work in small groups to develop the best way to represent their data. As a
class, we will create an appropriate graph based on their ideas using the class data.
Class discussion: What types of claims might we make based on our data? What
types of evidence might we look for in our analysis? How much evidence do we
need? In their journals, students will create claims and support them with evidence
from the collected data. Based on what they now know about SA:V ratios,
students will critique their original models and make revisions. How could you get
a bigger cell that was still efficient at nutrient uptake/waste removal, etc? In small
groups, students will develop ways to change the cell but still maintain high SA:V.
Students will identify problems they run into as they make these changes and
theorize about ways their model limits them? If enough time remains, students can
test their proposed models. Homework: Students will finish writing up their
claims and supporting evidence in their journals.
3.3 Students will understand and explain the importance and consequences of
surface area to volume ratios in cells.
1.3 Students will interpret scientific results and make conclusions based on
evidence.
1.5 Students will interpret graphs to recognize experimental conditions.
At this point in the inquiry, students have collected data and are ready to analyze
their results. I want to guide them through some effective ways to do this as
students often struggle with this aspect of experiment and may not have had
extensive experience with it. Additionally, I want students to discuss different
ways of representing their data and to analyze the benefits of using certain types of
graphs. I have found that students have gotten various amounts of instruction on
graph-making in junior high and I want all students to be able to effectively
distinguish and choose between different types of representation. Finally, I want
students to apply this concept to shapes other than cubes. From a previous
homework assignment, students should remember that many cells are not cuboidal
and can have other shapes that increase SA:V. I also want them to consider how
models often lose credibility at a more detailed level as one deepens one’s
thinking. I have chosen to use discussions and visuals as my primary instruction
methods here because I want students to work to solve problems themselves
instead of hearing solutions from me. I feel this will better be accomplished if
students are engaged in meaningful dialogue with one another.
I will perform an observational assessment during the group work portion of the
lesson to get a feel for the types and depth of student dialogue. Alternatively,
students will have their conclusions about the investigation recorded in their
journals.
Examples of graphs from scientific experiments, media, etc. (bar, line, pie, etc.),
lab ingredients from previous day if needed
DAY 8: (50 minutes) Cell Diversity; Introduction of Culminating Inquiry Project
1. What students are doing
Stewart
Students will begin class by sharing their ideas about cell shape with the class
(from the previous day). Students will then look at various types of cells both
under the microscope and in pictures and hypothesize about why the cell is the
way it is based on its environment. For example, students will look at a cell that is
fairly large and ask themselves, “What about this cell’s environment makes it
possible for the cell to be so large? How might this affect how the cell obtains
nutrients?” Students will record their ideas in their journals (along with drawings)
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Diffusion Unit
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
4. Evidence of understanding
5. Resources
and discuss their ideas with their small groups. Students will then read part 1 of
an article about the Pacific salmon life cycle and analyze the implications of
osmosis for the salmon in their small groups. Groups will predict how the salmon
might cope with the changing environments that it faces. Students will then read
part 2 of the salmon article to see whether their predictions are supported by
theory. Finally, students will receive and examine directions for the culminating
inquiry project due next week. Homework: Over the weekend, students will begin
work on their culminating projects.
3.5 Students will analyze the reasons for and types of adaptations cells make to
cope with their environments (related to benchmark 1.3.8).
Culminating Project meets Goals 1-4.
I feel that this lesson will help students apply the principles they have learned to
the natural world. The inquiry had students look at how SA:V is related to
diffusion in a model. Now I want them to see how this concept applies to real
organisms, i.e. not a model. I feel that this activity will help students to visualize
the larger picture of why we investigated diffusion and osmosis. I will need to
strategically choose cell types that have obvious adaptations for the microscope
activity. I also want students to be able to see that because cells are living, they
can often adapt to a changing environment, unlike an agar cube. Therefore, I have
chosen the salmon example as it is clear example of a changing environment and
most students will have firsthand experience with salmon from living in the Pacific
northwest. I will be able to refer to this lesson in future units (ex. adaptation and
evolution). I have chosen to ask questions and have students respond in their
journals so that I can see if students can apply what they have learned in the
inquiry to a new situation.
I will examine students’ journals to see how well they can apply their knowledge
of SA:V and diffusion/osmosis to a new situation.
Microscopes, slides and pictures of various cell types, salmon article parts 1 and 2
WEEK 3:
DAY 9: (50 minutes) Student work day
1. What students are doing
2. Objectives (no more than two,
numbered for example as 1.2, 3.1, etc.
from list on previous page )
3. Reasons for content and
instructional strategy
Stewart
Students will have a day to work on their culminating inquiry projects in class. At
this point, most of the work should be complete and students should have
organized their project over the weekend. In this class period, students will have a
chance to clarify any confusion they have by discussing their thoughts with their
peers or me. Students will also get help with how to use appropriate written
language in their projects. Near the end of class, the class will have a short
discussion about the effectiveness of group collaboration in scientific inquiry.
Students will analyze the advantages and disadvantages of working in groups to
solve problems and discuss ways in which real scientists work collaboratively.
Finally, students will fill out an exit survey recapping their experience and
attitudes toward their group’s work for this inquiry investigation. Homework:
Culminating projects are due during Block 2 (Wed. or Thurs.).
4.2 Students will use appropriate language in written expression.
5.3 Students will analyze the advantages and disadvantages of doing inquiry in a
group.
Culminating Project meets Goals 1-4.
I feel that I would be doing students a disfavor if I expected them to complete their
entire projects at home. Most of the work for their project should already be done
(and feedback provided by me) in their journals, but I still want students to have
every opportunity to get misconceptions cleared up and I want them to feel like
they can be proud of their work. Therefore, I want to give them plenty of work
time. Additionally, I want students to realize that group work is integral to inquiry
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Diffusion Unit
4. Evidence of understanding
5. Resources
(goal 5), but that group work is not always easy. I want students to see that group
work has both advantages and disadvantages, but to also see how effective it is for
students to build off one another’s ideas and share perceptions. The culminating
project is most appropriate at the end of the unit as students will need to rely on
what they have learned in order to meet the objectives of the project. Additionally,
students should now be able to relate the big ideas to the smaller details more
effectively.
1. Exit survey of group work, 2. Culminating projects: Inquiry reports
Exit surveys
***For certain students, I will accept their culminating project as an oral presentation to me instead of a written
presentation.
Stewart
11
Diffusion Unit
Pre-Planning Products
Diffusion & Osmosis and Cells
10th grade biology
Beth Stewart
EDTEP 587
TOPIC OF UNIT:
Stewart
12
Diffusion Unit
Relevant EALRs:
1.3 Changes in Matter and Energy: Understand how interactions within and among systems
cause changes in matter and energy.
The topic of diffusion is relevant to EALR 1.3 as diffusion is caused by the interactions
between molecules (matter) within a system and ultimately leads to a change in the
distribution of those molecules.
1.3.7
Life Processes and the Flow of Matter and Energy: Explain how organisms can
sustain life by obtaining, transporting, transforming, releasing, and eliminating
matter and energy.
This particular unit covers diffusion and osmosis in relation to cells. This
benchmark is appropriate for this topic as students will learn how cells obtain
and release matter through the processes of solute diffusion and osmosis.
2.1 Scientific Inquiry: Develop abilities necessary to do scientific inquiry.
Students will learn all aspects of guided inquiry in this unit. These skills encompass
questioning (2.1.1), designing and conducting investigations (2.1.2), explaining results
(2.1.3), modeling (2.1.4), and communication (2.1.5). After all, good inquiry should
include all of these. Please refer to EALR benchmarks.
3.1 Nature of Science: Understand the nature of scientific inquiry.
3.1.4
Evaluating Methods of Investigations: analyze and evaluate the quality and
standards of investigative designs, processes, and procedures.
While not part of an assessed objective, EALR 3.1 is relevant to this unit as
students are asked to constantly critique and revise their experimental designs
and models.
Relevant themes in ATLAS:
The following are all themes from the ATLAS that relate to this unit.
1. Every cell is covered by a membrane that controls what can enter and leave the cell. (CF)
2. The rate of reactions among atoms and molecules depends on how often they encounter
one another, which is affected by the concentration, pressure and temperature of the
reacting materials. (CR and CF)
3. An enormous variety of biological, chemical, and physical phenomena can be explained
by changes in the arrangement and motion of atoms and molecules. (CR)
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The following are themes from the ATLAS that are connected to this unit, but not directly
related to it.
4. Complex interactions among different kinds of molecules in the cell cause distinct cycles
of activity, such as growth and division. Cell behavior can also be affected by molecules
from other parts of the organism or even other organisms. (CF)
5. Within the cells are specialized parts for the transport of materials, energy capture and
release, protein building, waste disposal, passing information, and even movement. (CF)
6. Communication between cells is required to coordinate their diverse activities. Some
cells secrete substances that spread to nearby cells or are carried in the bloodstream to all
cells. (CO)
RATIONALE:
Transport in cells and the ability to regulate balance is integral to understanding how life
remains ordered. The ability to obtain energy and nutrients and to secrete wastes is crucial to all
living organisms. In fact, it is characteristic of life. Students need to realize and learn that
interaction with the environment is a big idea in science and one that classifies life (open
systems). Not only are there interactions on the level of ecosystems, but there are also
interactions between parts of a single organism (ex. organs or cells) and the surrounding
environments. Transport and regulation within cells (specifically diffusion and osmosis) show
the interaction between a cell and its extracellular environment. In order to better understand
cellular transport, students will need to understand the behaviors of atoms and molecules,
chemical reactions, concentrations, membrane functions, and cell communication. Students will
also need to understand the purposes for regulation and control. Additionally, students will be
able to use the ideas of osmosis and diffusion, transport, and regulation throughout the school
year. For example, they will learn about protein function, development, environmental effects
on ecosystems (ex. pollutants), hormone signaling, etc. All of these ideas incorporate the
principles of osmosis and diffusion.
These ideas will help students become more science literate citizens for a variety of
reasons. For example, understanding diffusion allows them to understand the dangers of
bioterrorism and pollution. Knowing about osmosis allows them to understand dehydration, salt
as a preservative, and desalination of sea water for drinking. Many of these are major societal
issues that citizens are asked to evaluate and many of them simply help us understand and
appreciate the complexity of our own bodies. Perhaps by learning about diffusion, students will
recognize how substances spread throughout the body and cause harm to many places other than
the area of ingestion. With this knowledge, students may become more conscious and concerned
about what they put into their bodies. Understanding that life is characterized by the
maintenance of balance will allow students to see that many ailments and problems in life are
caused by the disruption of this balance. Finally, developing experience with good scientific
inquiry will help students judge the validity of scientific results that they may encounter.
While some prerequisite skills and knowledge are mentioned above, others include basic
skills in designing and analyzing experiments. In order to design their own procedures for some
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of the investigations, students will need to have some familiarity with creating hypotheses,
designing experiments, and identifying variables. They will also need to have elementary
observational skills. As always, these skills should be continually practiced throughout the
school year. Previous topics in the year may include energy and nutrient transfer in ecosystems
(and homeostasis), populations biology, and body systems. Later topics may include DNA
function, genetic inheritance, development, and ecology.
CRITICAL ATTRIBUTES:
1. The process of diffusion is dependent upon the interactions between constantly and
randomly moving particles in a particular amount of space.
2. The rate of diffusion depends on how often particles encounter one another, which is
affected by the concentration, pressure, and temperature of the particles.
3. Cell membranes control the movement of specific solutes in controlled amounts and in
particular directions between the intracellular and extracellular environments.
4. Cells obtain nutrients, energy, and water and excrete wastes based on the difference in the
solute concentration gradient between the intracellular and extracellular environments.
5. The ability of cells to maintain homeostasis (through prompt nutrient uptake, ability to
release excess heat/waste efficiently, etc.) is governed by the relationship between
surface area and volume.
6. The relationship between the diffusion of solutes and water (osmosis) is determined by
the permeability of the membrane separating the two solutions.
DESCRIPTION OF CULMINATING PROJECT:
The culminating product for this unit will consist of an extensive lab report based on the
inquiry investigation, “What are cells so incredibly tiny?”, performed during the second week.
Throughout the unit, students will consistently produce work that will go into their final report.
Because of this, the culminating project will be more like a compilation of all of the essential
pieces from the quarter than a new project that students start at the end of the unit. Students will
need to integrate all of their learning throughout the unit into a final written report discussing
what they learned from the inquiry investigation. In certain cases, students will be allowed to
give oral presentations to demonstrate understanding instead. The basic pieces that must be
included in the final product are as follows:
1. The MAIN QUESTION asked in the inquiry
2. BACKGROUND KNOWLEDGE: an explanation of the process of diffusion on a
microscopic and macroscopic scale, including a drawing showing how molecules
interact, in what direction they diffuse, and why. (GOAL 2)
3. QUESTIONS raised during the investigation
4. HYPOTHESIS and PREDICTION (GOAL 1)
5. The EXPERIMENTAL DESIGN including a description of the MODEL (GOAL 1)
6. DATA, including any representations (tables, graphs, etc.) (GOAL 1)
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7. FINAL CLAIM and SUPPORTING EVIDENCE (GOAL 1)
-Include a statement of where this evidence is found in the data and how it
answers the main question.
8. REVISED MODEL (GOAL 1)
9. Suggestions for future research
10. A description of how the model is like a cell. (GOAL 3)
- Include an explanation for the purpose and function of the cell membrane and a
drawing showing how the membrane is able to regulate what enters or leaves the
cell.
The report must appropriately communicate the essential ideas to the reader in an organized
fashion (GOAL 4). Students will receive more extensive directions and a scoring rubric. This
performance assessment is an authentic task as scientists are constantly writing reports based on
their investigations in order to communicate their findings to others. Students will meet 4 of the
5 goals and demonstrate knowledge of critical attributes 1, 3, 4, and 5 in this final product.
ESSENTIAL QUESTIONS:
Why can’t you dispose of chemicals too near to a lake, river, or ocean (for example, when you
are camping)? Or wash your car where the suds will get into the water? What happens to these
chemicals after they get into the water? How do they end up contaminating so many organisms
in such a large area?
These are questions that are relevant to students’ lives. Many household products must be
disposed of in careful ways to prevent them from contaminating our waterways. Students need
to understand the catastrophic effect that can be caused by contamination by these chemicals. In
order to answer this question, students will need to examine how molecules (and therefore, these
chemicals) can spread throughout the water through the process of diffusion, effectively
contaminating a much larger area than the area where the chemical was dumped. They will also
examine how factors like temperature can affect this process. Students will also need to know
how molecules can get inside of organisms, specifically inside of cells. Therefore, students will
need to learn how molecules can and cannot pass through membranes.
Why are cells so incredibly tiny?
This is the question students will be answering in their inquiry investigation. Students will learn
that cells are small in order to facilitate quick nutrient and energy exchange. They can connect
this idea back to the water contamination question by realizing that chemicals will also diffuse
throughout a cell quickly based on its small size. Therefore, students will be able to see how
small size is both integral to the cell’s survival and damaging in other respects.
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