investigate the effect of solute concentration on the rate and direction of osmosis.

Purpose:

To investigate the effect of solute concentration on the rate and direction of osmosis.

Materials:

– 1 artificial cell containing tap water

– 1 green artificial cell containing 30% sucrose

– 2 – 400 ml beakers

– Tap water – 30% sucrose solution (green)

– 1 triple beam balance

– Paper towel

– Tweezers

– Pyrex glass dish

 

The artificial cells are made from dialysis tubing, which is a type of engineered plastic with very small holes, which some molecules can pass through. In this case, water molecules are able to pass through but not molecules of sucrose.

 

Method:

 

• In one 400 ml beaker, add 300 ml of water. In the other beaker, add 300 ml of the tinted 30% sucrose solution.
• Using tweezers, take one artificial cell containing tap water (un-tinted) and quickly dry it with a paper towel and place it on the Pyrex tray. Take one artificial cell containing 30% sucrose solution (tinted) and quickly dry it with a paper towel and place it on the same Pyrex tray.
• Carefully weigh each cell on the triple beam balance to the nearest tenth of a gram. Record the weights in Table 1. Place the cells back on the Pyrex tray.
• Pick up each of the two cells and place them in the opposite beaker. The artificial cell containing the un-tinted water is to be placed into the tinted 30% sucrose solution and the artificial cell containing the 30% sucrose solution is to be placed into the beaker containing tap water. Note and record the time.
• After 45 minutes, remove each cell from its beaker, dry them by quickly rolling them on a paper towel and place them on the Pyrex tray. 6) Carefully weigh each cell to the nearest tenth of a gram and record the weights in Table 1 on the next page. 7) Calculate the gain or loss in weight and calculate the percent increase or decrease in Table 1. Include the (–) sign for negative values.

Questions (To be answered within the Discussion portion of your lab):

• Did cell(s) gain or lose weight?
• Is this what you expected? Give reasons for your answer using your data.
• Is the percentage gain about the same as the percentage loss? Is this what you expected, given that the differences in tonicity (concentration gradient) between the cells and the solutions in the beakers were the same? (0% cell -30%solution and 30%cell -0% solution)
• Do your data support or refute your hypotheses for rate and direction of osmosis?
• Theoretically, could the cells or solutions be recycled, just as they are, for another lab? Explain
• Is the 30% sucrose cell still 30% sucrose at the end of the lab? Explain