Lab Desgin
Research Question
When solutions between a partially permeable membrane has different concentration gradient,
a passive transport called osmosis occur to equal the concentration. This causes the water
molecules to move from higher concentration gradient solution to lower concentration
gradient solution. Osmosis eventually stops when the both solution have equal concentration.
Hypothesis
Solutions with different concentration gradient will cause water molecules to move from
higher concentrated solution to lower concentrated solution through a partially permeable
membrane and result in equal gradient. However, since this is a movement of molecules the
temperature will affect the rate of the osmosis process.
Prediction
Water molecules from dialysis tube will transported out of the tube since the solution inside
the dialysis tube will have higher concentration gradient than the outside of the tube.
Therefore, the amount of the water in dialysis tube will decrease and the amount of water
outside of the tube will increase. Experiments that are done in high temperature room will
show faster rate of osmosis than experiments that are done in low temperature room.
Variables
-Independent: the concentration gradient of the solution outside and inside of the dialysis tube
-Dependent: the rate of osmosis
-Controlled: the temperature of the surrounding
Apparatus
-Metarials
One 6- inch dialysis tube, 400mL beaker, string, distilled water, salt, food coloring, lab
stands, holders, balances, and thermometer.
1
Procedure
1)
2)
3)
4)
5)
6)
Make sure everything is surrounded by a room temperature, 72° F
Pour 150mL of distilled water into the 400mL beaker.
Use the balance to measure 3g of salt and add it to the water and stir.
Add two drops of blue food coloring to the beaker.
Measure the total weight of the beaker using the balance and record
Tie a knot to one end of the dialysis tube and fill 100mL of distilled water in to the 6
inch dialysis tube.
7) Then, by using the balance, measure 1g of salt, and add it into the dialysis tube.
8) Tie the top of the dialysis tube and measure its weight using the balance and record.
9) Tie a piece of string to the top of the dialysis tube, and drop the tube in the beaker.
10) Tie the string to the lab holders, make sure that the tube is still in the beaker water
and the tube is stood up vertically.
11) Check in every 30 minute and measure the weight of the tube, weight of the beaker
without the tube, and the amount of the water in the beaker without the tube. Record.
12) Repeat 11) until it shows no change.
13) Repeat 1) through 12) four more times in total of five trials.
14) Change the room temperature to 52° F and repeat step 2) through 13).
15) Change the room temperature to 92° F and repeat step 2) through 13).
2