Hypotheses are developed based on observations of the world. Sometimes, a hypothesis can be developed based on the observations made by others. For this activity you will use your knowledge of osmosis to generate a hypothesis and prediction. You will then test that hypothesis and assess the data.

Tasks:

1. Develop a hypothesis and prediction based on your knowledge of osmosis.
2. Decide on a method of data collection that will allow you to test your hypothesis.
3. Collect, record, and analyze data.
4. Evaluate the outcome of your experiment relative to your hypothesis.

Materials:

- Celery (one bunch)
- 4 cups/containers capable of holding at least 1 cup (240ml) of fluid
- Water
- Salt
- Food coloring (red or blue, if possible)

Instructions – Part 1:

1. Review what you know about osmosis. Refer back to notes or your textbook.
2. Write a hypothesis based on that knowledge in your own words.
3. Develop a prediction for the behavior of a stalk of celery under one of the treatment conditions listed below based on that hypothesis.

Treatment Conditions:

- Control: 0 tsp salt, 1 cup water, 1 drop food coloring (isotonic)
- Hypotonic: ¼ tsp salt, 1 cup water, 1 drop food coloring
- Isotonic: 1/8 tsp salt, 1 cup water, 1 drop food coloring
- Hypertonic: 1 tsp salt, 1 cup water, 1 drop food coloring

Observation Report:

- Summarize your understanding of osmosis in your own words.
- State your hypothesis and prediction.
- Briefly summarize your observations both verbally and through drawings.
- Discuss whether your prediction was accurate and whether your hypothesis was supported. Explain why or why not.
- Propose a more quantitative experiment to measure the effect of osmosis. You are not limited to using equipment and materials that you have on hand in your house.