Under What Conditions Does Osmosis Occur?

Under What Conditions Does Osmosis Occur?

Biology Lab 9 (Part 1)

Objective: To observe the movement into or out of a grape under different conditions.

Materials:

3 grapes3 small jars with lidssaturated sugar solution

Grape juicetap watermarking pen

Paper towelbalance

Data Table 1

Procedure:

1. In your lab notebook, copy Data Table 1. Label the rows: grape juice, sugar solution, and water.
2. Fill one jar with grape juice. Fill the second jar with the sugar solution. Fill the third jar with tap water. Label each jar with the marking pen according to the solution it contains.
3. Using the balance, find the mass of each grape. Record this data in your data table under “original mass.” Place one grape in each jar. Put a lid on each jar.
4. Predict whether the mass of each grape will increase or decrease over time. Place the prediction under the “predicted mass” column. Explain your predictions.
5. After 24 hours, remove each grape from its jar, and dry it gently with a paper towel. Using the balance, find its mass again. Record your results under the column labeled “actual mass.”
6. Clean up your material before leaving the lab. Throw the grape in the trash. Rinse out each jar and place it on the drying rack.

Observation and Analysis Questions:

1. Define osmosis.
2. Identify the solution in which osmosis occurred.
3. How did you determine whether osmosis occurred in each of the three solutions?
4. Evaluate your “predicted mass” hypothesis. Has your thinking changed after having seen the data? Explain how.

Why is salt water not suitable for drinking?

Biology lab 9 (Part 2)

Objective: To use potatoes to determine why it is unsafe to drink salt water.

Hypothesis:

Materials:

2 potato slices2 beakers10 g of NaCl

Scale

Data Table 2

Procedure:

1. Cut a potato into equal pieces.
2. Prepare 2 beakers, one with 10g of salt dissolved in 250mL of water (this equals the approximate concentration of sea water).
3. Fill beaker 2 (the control) with 250 mL of tap water.
4. Using the scale, weigh each potato and record their mass in Data Table 2.
5. Place one potato in each beaker, making sure to put the right potato in the pre-determined solution.
6. Let the beakers stand overnight. On your lab, make a hypothesis as to what you think will might happen to your potatoes.
7. The next day, observe the texture of the potatoes. Blot the pieces dry and determine the mass of each piece. Compare this to their original mass.

Analysis Questions:

1. Explain what happened to the potatoes in the tap water and the salt water. Were there any differences in texture between the potatoes?
2. Why shouldn’t people drink salt water?