United Nations Intern School
New York, NY
(Modified by Elke Bergholz from AP Laboratory Book)
Type of entry
Lesson, class activity
Type of activity
The following questions will the student be able to answer:
What is osmosis?
How can we demonstrate the movement of water molecules?
What are hypotonic, hypertonic, and isotonic solutions in our environment?
Do salt water fish drink and how do fresh water organism survive in their environment?
What are the physiological adaptations of these organisms that makes them survive in their environment?
How can we demonstrate what happens to salt water fish and a fresh water paramecium?
(How do I prepare solutions? )
Notes to the teacher:
This activity can be done with students of the 7th to 10th grade. It can be presented as a prepared lab with instructions or can be developed by the students depending of their ability.
Preparation time needed: 30- 45 min to prepare sucrose solutions(or less if students prepare solutions.
Class time needed: 2 times 30 - 45 minutes, periods must be on two cosecutive days.
Required of students: Hands-on activity, preparation of solutions; preparing potato cores, mass recording, lab set up that will demonstrate and answer the questions listed above.
Abstract of Activity:
Students will demonstrate or inquire if salt water fish drink or not. If the salt water fish is hypotonic then it must loose water. The ocean and the salt water fish will be demonstrated by using sucrose solutions and potato cores. The loss or gain of water will be detected by the loss or gain of mass of the potatoe cores. This will be achieved by preparing potato cores which will be placed in different sucrose solutions.The following is an example of what could be required from students. The outline could be altered depending on how much the students is to achieve.
water, 0.2M and 1.0M sucrose solution
Objective: to be able to answer the question: Do salt water fish drink?
cut 3X3 potato cores
record the mass of each set of 3 cores
place each 3 sets in
ii) 0.2M sucrose solution
iii) 1.0M sucrose solution
cover and record the mass after 24 hours.
collect data in a table
construct a graph
What accounts for the movement of water molecules?
Identify which area of the graph presents oceans and which lakes.
State a hypothesis how salt water fish and frsh water organisms might survive in their environment?
Method of evaluation:
discussions during the lab
Extension/ Reinforcement/ Additional ideas:
Research on adaptive organs to different environments of different organisms.
Hypertonic and hypotonic solutions in the human body.