Hypothesis Testing

HYPOTHESIS TESTING Osmosis 30pts 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 ● Develop a hypothesis and prediction based on your knowledge of osmosis ● Decide on a method of data collection that will allow you to test your hypothesis ● Collect, record, and analyze data ● Evaluate the outcome of your experiment relative to your hypothesis Materials For this activity you will need the following: ● Celery (one bunch) ● 4 cups/containers capable of holding at least 1cp of fluid ● Water ● Salt ● Food color (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 USING YOUR OWN WORDS. -If celery is placed in a hypertonic salt solution, it will wilt more compared to celery in a hypotonic or isotonic water solution because the salt solution has lower water concentration. 3. Develop a prediction for the behavior of a stalk of celery under one of the treatment conditions listed below based on that hypothesis. -The celery in the hypertonic salt solution will shrink and become softer while the celery in the hypotonic and isotonic water solution will stay firm and remain hydrated. Condition Salt Water Food Coloring Control 0 1 cp (8 oz) (240ml) 1 drop Isotonic ¼ tsp 1 cp (8 oz) (240ml) 1 drop Hypotonic 1/8 tsp 1 cp (8 oz) (240ml) 1 drop Hypertonic 1 tsp 1 cp (8 oz) (240ml) 1 drop Part 2 1. Use the information in the table above to set up a control and four treatment conditions. One condition per cup/container. Stir each solution well to dissolve the salt and distribute the food coloring (if used) BIOL 151 Sp2021

2. Remove a stalk of celery from the bunch and cut the top and bottom of the stalk leaving a 15-18cm length (~ 6-8 inches). Cut below any leaves that might be at the top of the stalk. 3. Place one length of celery into each container of water. Orient the stalk so the bottom of the stalk (wider end) is submerged in the water and the top (narrower end) is above the water level. 4. Note the day and time that you started the experiment 5. Visually monitor the celery over time making qualitative observations. 6. Record your observations IN WORDS AND IN DRAWINGS. Include a scale bar in your drawing 1. Draw the Containers: Draw four cups or containers. Label them as Control, Salt Solution, Water, and Food Coloring Solution. 2. Celery Stalk: Draw a long, vertical rectangle representing the celery stalk. 3. Water Level: Draw a horizontal line inside each container to represent the water level. 4. Labeling: Label the wider end of the celery stalk as the bottom (submerged in the water) and the narrower end as the top (above the water level). 5. Scale Bar: Include a scale bar, a small line with a number indicating the length it represents, to show the size accurately. Part 3 1. Cut another stalk of celery into four short segments of about 3cm (1inch) each. 2. Drop one short segment into each of the four treatment containers. 3. Remove the segment of celery from the water at the point in time that you observe a noticeable change in the larger celery stalk. 4. Make qualitative observations of the celery segment. Qualitative measures include touch. What happens if you apply pressure to the celery segment? -The celery piece submerged in the hypertonic salt solution feels notably flexible and softer to the touch. The celery piece bends easily when you apply light pressure its almost decaying in your palm. On the other hand the celery segment in the hypotonic water solution feels sturdy and firm. It doesn't bend as easy and stays firm when pressure is applied. The celery segment in the hypertonic solution has become more delicate and less pressure-resistant due to the loss of structure, shown by the change in texture and reaction to pressure. 5. Record your observations IN WORDS. Observation Report 1. Summarize your understanding of osmosis. Explain the concept USING YOUR OWN WORDS. 2. State your hypothesis and prediction 3. Briefly summarize your observations IN WORDS AND IN DRAWINGS. Was your prediction accurate? 4. Discuss whether your hypothesis was supported. Explain why or why not. 5. Propose an experiment that would be more quantitative. How could you measure the effect of osmosis? You can propose any (reasonable) experiment. You are not limited to using equipment and materials that you have on hand in your house. BIOL 151 Sp2021