Title: Osmosis in Carrots(Rashida Madraswala)
1a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.
Baby Carrots(grocery store)
Distilled Water(grocery store)
Plastic Cups(grocery store)
Digital Balance (Ward's Scientific)
Graduated Cylinder or Beaker for measuring volume (Ward's Scientific)
Think of when someone has a sore throat. A common home remedy is to gargle with salt water. Use the concept of osmosis to explain why this remedy works.
(Answer should mention that a sore throat is the result of swollen throat tissues. Salt water has a lower concentration of water than the tissues and the water moves out of the tissues by osmosis. This should decrease the swelling and the pain associated with it.)
In the following lab, you will observe and measure osmosis in a carrot. Predict what will happen to the carrots after they have sat in each of the 4 different solutions.
1. Weigh 4 carrots and record the weight of each carrot in the data table below. Place each one in one of the four solutions, noting which carrot is in which solution.
2. Wait 25 minutes. Remove the carrots and blot them dry. Remember which one came from which solution. Record the weight of each after in the table above.
3. Calculate the % change in mass.
change in mass = (final mass - initial mass)/initial mass
% change in mass = change in mass x 100
4. Graph the data. Determine what variable goes on the X-axis and what variable goes on the Y-axis.
Answer: Since we are using different carrots for each solution, they will have different initial mass. Therefore, when comparing across solutions we need to examine the percent change to equalize for the variability of initial mass.
2. List and explain three sources of error in this lab.
Answer: 1. Improperly made solutions. If the solutions are not as described then the graph may not show a clear relationship. 2. Mixing up the carrots. If the carrots were switched, the data would not be accurate. 3. Forgetting to dry the carrots before weighing would add excess weight not attributed to osmosis.
3. Which solution was hypertonic to the carrot cells? Which solution was hypotonic?
Answer: This will depend on the experimental results. Mathematically, any percent change in mass greater than 100% will be hypotonic and any percent change in mass less than 100% will be hypertonic.
2. Preservation of Foods. Salt solutions are used to preserve vegetables. The high salt concentrations are hypertonic to bacterial cells and kill them before they can spoil the food.
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.
Videos: Include links to videos posted on the web that relate to your activity. These can be videos you have made or ones others have made.
Google Docs for entering data and graphing.
References: Lab activity adapted from Mrs. Turner-Graham, El Camino Real HS