Biology - HOT Science Lab

Teacher
Diffusion and Osmosis
NGSSS:
SC.912.L.14.3 Compare and contrast the general structures of plant and animal cells. Compare
and contrast the general structures of prokaryotic and eukaryotic cells. (AA)
Purpose of the Lab/Activity:
Address the movement of material through a semi-permeable membrane.
To observe the process of osmosis and how it occurs in cells.
Examine and describe the different environmental conditions that can affect a cell and its
processes.
Prerequisites:
The movement of ions and molecules across membranes is discussed.
Iodine indicator is used to test for the presence of starch. It turns blue-black when starch
is present.
Basic understanding of the structure and function of cells.
Materials (per group):
open space
Procedures: Day of Activity:
Before
activity:
During
activity:
What the teacher will do:
a. Activate student‘s prior knowledge by the following demonstration.
b. Drop several drops of food coloring into a glass beaker of water. Ask
students to observe what happens over the next couple of minutes and
have them note changes to water and food coloring in their journals. Have
students predict what will happen after 5, 10 and 20 minutes. Introduce the
concept of ―diffusion‖.
c. Define and tell students that we will be exploring how diffusion occurs in
different
d. For activity #2, it is suggested that the teacher prepare the potato core
samples using a cork borer prior to the activity.
e. Ask the following questions:
1. Describe the function of the cell membrane.
2. Discuss how cell membranes are like a filter or gatekeeper.
3. Why is such a function necessary for a cell to function
4. Define ―selectively permeable.‖ Hint: dissect the word parts and then
explain its meaning)
What the teacher will do:
a. Monitor students to make sure they are remaining on task and are following
proper lab protocol.
b. Review the experimental design diagram by asking individual students in
groups to explain the different parts of the experiment.
1. Follow laboratory procedural plan; making sure to model proper
laboratory safety and use of equipment.
2. Emphasize importance of data collection by groups.
Biology HSL Page 158
Curriculum and Instruction