Osmosis/Diffusion Stations

You have 10 minutes to complete each mini lab station. Work collaboratively. Work neatly. Work efficiently. Work carefully.

Station 1: EGGSPERIMENT WITH a CELL- 10 min *READ THROUGH FIRST* One of the cell structures you are learning about is the cell membrane. In the Project, you will model how a cell membrane works to let water enter and leave the cell. You will use a chicken egg as a model of a cell. After dissolving the shell in vinegar to expose the membrane, you will soak the egg in various liquids and observe how the size and mass of the egg changes as it takes on or loses water through the membrane. You also will keep a record of observations and measurements of the egg. PROCEEDURE As soon as you get your egg, observe its features and measure its circumference. Record your observations and measurements (should be detailed and precise). Place your egg cell in a cup. Place your group names on the cup. Pour vinegar over the egg until it is covered. This will dissolve the hard shell, leaving only the membrane. Soak the egg in vinegar for at least two days. Then observe and record how the egg has changed, including any changes in appearance or texture. Also measure the circumference of the egg, using the procedure described on the bottom of the page. Record your observations and measurements. Soak the egg in colored water for one or two days. Observe and record how the egg has changed and. measure and record its circumference. Soak the egg in salt water, and corn syrup at least one day each. Continue to keep careful records of observations and measurements of the egg’s circumference and other qualities. Graph the data you have collected and prepare a report of your results. Be prepared to explain your results and show your egg to the class. HINTS For the best results in this project, it is important to measure your egg carefully each day. This is because changes in circumference of the egg may be slight, and measurements that are not precise may mask changes that have occurred. Follow these steps when measuring the egg each day. 1. Carefully take the egg out of the liquid and pour the liquid down the drain (or in our class the bucket). 2. Rinse off the egg in cold water and blot it dry with a paper towel. 3. Using a measuring tape, measure the circumference of the egg in cm to the nearest.0. Wrap the tape snugly around the middle of the egg at the equator but be careful not to cut into the egg’s membrane with the tape. 4. Record your measurements and any other observations about the egg in the data table. 5. Return your egg to the container and cover it with another liquid, according to the project rules above.

Station 2: Diffusion Demo- 10 min Page 15 of your packet Make your 3 hypothesis Put water ¾ full in each of the 3 beakers Place a hard candy in one, a sugar cube in one, and a drop of food coloring in one. Make observations Respond to analysis questions

Station 3: Diffusion Journal & HW CHECK- 10 min On warm up An investigation was set up to determine the movement of water through a membrane. The results are shown in the diagram.  The picture above demonstrates the amount of STARCH and WATER in a typical blood cell. Observe what happens to the cell in each solution. Use what you see happening to the blood cell in starch solutions and apply this information to sugary solutions of water. In terms of the cell and diffusion, what do you think drinking a very sugary soft drink will do to your cells? Explain how you came to that conclusion.

Station 4: Fluffy Raisin and Carrot Demo- 10 min Complete page 18 in your packet by observing the raisins, then the carrots. You may need to gently bend the carrots to see the difference. Be specific in your conclusion about what happened. Remember to compare to the control samples!