Activities
Demonstration Lab
Purpose: The purpose of this lab will be to introduce students to osmosis and diffusion using chicken eggs, since they are visible to the naked eye. This demonstration is "the hook" that can be used as a reference point throughout the rest of the unit.
Procedures (for the teacher):
1. Soak 2 chicken eggs in vinegar for 24-48 hours in order to dissolve the shell.
2. Have students measure the mass of each egg after the shell has been removed. (To save time, the teacher could measure the mass and give the data to the students.) Have students record the mass of each egg. Be sure to point out that the egg is a very large cell and it is surrounded by a cell membrane.
3. Create 2 different beakers with each of the following solutions: water and corn syrup and distilled water.
4. Measure the mass of each solution.
5. Place 1 egg into each beaker and let them sit overnight.
6. After at least 24 hours, remove the eggs from the solution.
7. Find the mass of the eggs and the remaining solution.
Questions for students:
1. What happened to the size of the egg when placed in the corn syrup?
2. What happened to the size of the egg when placed in the distilled water?
3. A hypertonic solution is one where there are more solutes compared to the inside of the cell. Which solution was hypertonic?
4. A hypotonic solution is one where there are less solutes compared to the inside of the cell. Which solution was hypotonic?
5. What could you do to make the cell (egg) get larger?
6. What could you do to make the cell (egg) get even smaller?
7. What do you think would happen if you placed the cell in really salty water?
Potato Lab
In between the egg lab and The Potato Lab, students should have some form of instruction that covers the specifics of what is able to enter and exit the cell and what equilibrium is. Prior to beginning this lab, remind students that potatoes are living, so they are made out of cells. Students may also need to be reminded that cells contain a number of solutes.
Procedure for students:
1. Cut out 2 small potato cubes that are roughly the same size. (In my classroom, I would cut these myself).
2. Find the mass of each potato cube.
3. In a beaker, pour in 100 ml of water. Add salt in order to make a saturated solution. This will be beaker 1.
4. In another beaker, pour 100 ml of distilled water. This will be beaker 2.
5. Add one potato cube to each beaker.
6. Let the potatoes sit for at least 24 hours.
7. After 24 hours, measure the mass of the two potatoes.
Pre and Post Lab Questions:
1. In which beaker is the solution hypertonic?
2. In which beaker is the solution hypotonic?
3. What happened to the mass of each potato?
4. Explain why the mass of each potato changed using what you know about osmosis.
Writing Assignment- The Story of Pee
Students will receive notes on kidney function and how pee is made. These notes will be used by students in order to make a short book explaining how pee is made. They will trace their lunch, including the water they drink, from the time they eat the food to the digested food particles entering the bloodstream and ultimately the kidneys. This activity can easily be differentiated based on the level of the students. Some students may need additional diagrams and flow charts to help them follow all of the steps.
Dialysis Lab/ Guest Speaker
Prior to this lab, students should briefly be exposed to some of the causes of kidney failure and a short explanation of kidney dialysis. I will also get a guest speaker from the community to come talk to my students. The guest speaker will be someone from a dialysis lab. This will help provide students with some of the background information necessary for understanding the lab.
In the following lab, students will experiment with a simulation of kidney dialysis, using artificial blood and a dialysate. For the purposes of my classroom, we will only focus only the salt, proteins, red blood cells and urea in the blood 3 4.
Procedure:
1. Students will make "artificial blood" by combining the following ingredients in a large test tube:
1. 2 mL of table salt
2. 2 mL of "protein" (baking soda)
3. Approximately 1 teaspoon of red glitter or sequins to represent red blood cells
4. 2 drops of yellow or orange food coloring to represent urea and other waste
5. Enough warm water to fill the test tube up
2. Place a stopper in the test tube and gently shake the "blood".
3. Obtain a piece of dialysis tubing. Wet one end and tie a knot.
4. Pour the "blood" into the dialysis tubing and tie another knot at the top of the tubing so that it is sealed. This represents the blood that would be removed from the body during dialysis.
5. Place the dialysis tubing into a cup of warm distilled water and let it sit for 10 minutes.
6. At the end of the 10 minutes, test the dialysate to see if it contains each solute. Read each question below for directions on how to determine if the solute left the blood.
a. If any of the urea or waste products left the blood, the dialysate would be orange/yellow. Did the urea leave the blood?
b. Dip the salt indicator strip into the dialysate. Did the salt leave the blood?
c. Dip the chromatography paper into the dialysate. If it turns blue, protein is present. If it remains white, protein is not present. Did the protein leave the blood? (The chromatography paper will not change colors. You could also call it "protein indicator paper".)
d. Observe the dialysate. Did any red blood cells move through the membrane?
Post Lab Questions:
1. Why do you think the protein did not move through the membrane but the salt did?
2. Do you think all of the salt left the blood? How do you know?
3. How would you change the dialysate if you wanted more salt to remain in the blood?
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