Name: _______________________________________________ Date: _____________________
IB Biology: Lab #1 (Osmosis & Surface Area:Volume)
Questions:
1. How does the size/number of cubes affect the surface area to volume ratio?
2. How does the tonicity of water affect the size of gummy bears?
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Directions:
Follow the steps found below to learn more about cells (in particular,
osmosis across a membrane, and surface area:volume ratio).
Each student will need to individually turn in an informal lab write-up, so it is
important for all group members to write down any data.
You should answer questions and record data in your notebook under the
“lab” section.
Part 1: Osmosis Lab Setup
Introduction:
For the first part of your lab, you will do an experiment to better understand the
concept of osmosis, which we will be learning about as we discover how cell
transport through the membrane functions.
1.
2.
3.
4.
Fill up 3 cups with water (2 with bottled, and 1 with tap).
Add about 1 tablespoon of salt to only one of the distilled water cups.
Label the cups as follows: Bottled water, Salt water, Tap water.
Measure the original size of all gummy bears. (Note: It is best to use 3
different colors so you are more easily able to differentiate between the
gummy bears you’re using!).
5. Copy the following chart into your notebook:
Gummy Bear #1
Length: _______
Color: ____________ Width: ________
Gummy Bear #2
Length: _______
Color: ____________ Width: ________
Gummy Bear #3: Length: _______
Color: ____________ Width: ________
6. You will be placing 1 gummy bear in each cup of water, and letting it sit
overnight. (Place gummy bear #1 into bottled water, #2 into salt water, and
#3 into tap water). Make a hypothesis (in your notebook) to predict what you
think will happen to the size of each gummy bear.
7. Let the cups sit overnight by either taking them home or bringing them to
Meghan’s office. We will check back on the gummy bears in tomorrow’s class.
Part 2: Surface Area to Volume Ratio
Introduction:
To better understand surface area to volume ratio, we will be measuring the surface
area and the volume of cubes of different sizes. Remember that….
 Surface area is the total area of the OUTSIDE of an object. (For example, how
much wrapping paper you would need to wrap a gift).
 Volume is how much space is found INSIDE an object. (For example, how
much water fills up a water bottle).
Important Equations:
Surface Area = Area of all sides of the cube added together
Volume= Length x Width x Height
You will be finding the surface area and volume of the following shapes:
1. Before you begin, copy the following chart in your notebook.
Figure
Total number Surface area Volume of
of cubes
of figure (=6 figure (=
x length x
length x
width)
width x
height)
A
B
C
Surface Area
to volume
ratio (=SA/V)
2. First, measure the SURFACE AREA of one cube. How do you measure
surface area?
a. Find the area of one side of the cube by measuring the length and
width (Record the area in your notebook).
b. Multiply the area by 6 (for all 6 sides). Record this in your notebook
(on the chart) as surface area of 1 cube. (Note: If you are doing this
experiment with rectangular shape instead of a cube, you will need to
find the length and width of each side and add up all areas).
c. Find the volume of one cube by multiplying length x width x height.
d. Find the surface area to volume ratio by dividing Surface
Area/Volume
3. Next, construct figure B (as found above).
a. Follow the same steps as in #2 to find the surface area and volume.
Record your data in your notebook.
b. Find the Surface Area/Volume ratio.
4. Next, construct figure C, and follow the same steps as above.
Analysis Questions:
Directions: Answer the following questions in your notebook.
1.
2.
3.
4.
What happened to the surface area as the size increased?
What happened to the volume as the size increased?
What happened to the surface area to volume ratio as the size increased?
Now imagine you’re looking at a very large cell. Next to it is a very small cell.
Which one has a larger surface area to volume ratio?
5. Why do you think this is? (#4).
Done early & want to earn extra credit points?
 Find 3-5 additional objects around the classroom.
 Measure the surface area & volume of each. Then, find the surface area to
volume ratio. Record all information in your notebook.
o Note: You will need to research how to measure the surface area and
volume of unusual shapes. Ask Meghan for help with this if you need
it!
Part 3: Osmosis Lab (Data Collection)
1. Now that the gummy bears have been in water for 24 hours, it is time to
measure the size of each gummy bear. Copy the following chart into your
notebook. Measure the length and width of each gummy bear, and record
your data.
Original gummy
bear size
New gummy
bear size
Overall change in size
(did the gummy bear
grow, shrink, or stay the
same?)
Gummy Bear #1:
(bottled water)
Gummy Bear #2:
(salt water)
Gummy Bear #3:
(tap water)
Osmosis Lab Analysis Questions:
1. What does osmosis mean? (explain in detail what osmosis is).
2. What does diffusion mean?
3. Overall, explained what you observed with the gummy bear found in:
a. Bottled water
b. Salt water
c. Tap water
4. For each gummy bear, explain what happened with the flow of water. (For
example, did the water flow into the gummy bear, out of it, or evenly into and
out of the gummy bear?) Why do you think this happened?
a. Sketch a diagram that represents the flow of water for each gummy
bear.
5. Research the following terms: hypotonic, hypertonic, & isotonic. Write the
definition of each. Then, explain which term applies to each of the water
solutions used in this experiment. Describe how the tonicity of the water
affected what happened to the size of the gummy bear.
a. For example: Because the water was hypertonic compared the gummy
bear, the water flowed _______(in which direction), causing the size of
the gummy bear to ______ (increase/decrease).
Lab Write-Up:
When you complete the entire experiment, write an informal lab report that
includes the following information:
 Scientific Questions (as written in the lab instructions).
 Hypothesis (for both parts of the lab).
 Materials
 Controls, independent variables, & dependent variables (for both parts of the
lab).
 Experimental Steps
 Data (written in the form of labeled tables).
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Analysis Questions
Conclusion
o Overall, what did you learn from the lab? (In this section, you should
make sure to answer the scientific questions in detail).
o What are some potential sources of experimental error?
o If you were to repeat this lab, what would you do so that your results
are more reliable?
*Your lab report must be typed, double spaced, done individually, and in APA format
(including a section for sources).
*You will be given a rubric for your lab write-up ahead of time.