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Osmosis Lab Report

Updated 12/24/14

Name: ________________________

Date: _________________________

Purpose

The purpose of this lab report is to apply the scientific method to observe and report on the process of osmosis. De-shelled eggs are used to investigate the effect of osmosis in cells in different solutions.

Directions

Please read all the Osmosis Lab instructions before beginning your experiment. View the “Cell Structure and Function” virtual lab. Use this report form to record your predictions, observations, analysis, and conclusions. Please leave the report prompts intact and simply type your responses under each prompt. Because this report form is standard, Turnitin will flag it with a large overlap score. Do not concern yourself with this issue for this report.

Expected Observations (3 points)

Reflect on your readings related to osmosis and cell membranes. Consider the three solutions in which you will immerse eggs. Briefly explain what you think you will happen to the different eggs under the different conditions. Be as specific and as detailed as possible. Use the understanding of osmosis that you have developed from reading the Lab instructions and viewing the “Cell Structure and Function” virtual lab.

Materials and Methods

See the Osmosis Lab Instructions document for materials and methods. A metric ruler will be necessary to measure the eggs’ diameters in centimeters.

Results (22 points)

Use the tables below to record your observations of the eggs after Part 1 of the Lab and after Part 2 of the Lab.

Part 1 Results

a. Record below any change in the physical characteristics of the eggs after they were immersed in vinegar for approximately 48 hours. Also note any change in the physical characteristics of the vinegar after this process.

b. Record the measurements of the circumferences of your eggs in Table 1.1 before you place each of them in an experimental solution but after removing their shells with vinegar. Find the average value of the circumference of each egg by adding the three measurements of each egg and dividing that number by three. Estimate the uncertainty in your measurement by subtracting your lowest measurement value for each from your average value for that egg. Record your measurement average and uncertainty in Table 1.2. Be careful: The eggs are slippery and fragile!

Table 1.1 Egg circumference measurements (in centimeters, before treatment)

Measurement	Egg A	Egg B	Egg C
Measurement #1 (cm)
Measurement #2 (cm)
Measurement #3 (cm)

Table 1.2 Egg circumference average value and uncertainty (before treatment)

	Egg A	Egg B	Egg C
Average value (cm)
Uncertainty (cm)

c. Record the height of each of the experimental solutions you prepare before placing the eggs in solutions.

Table 1.3 Solution height measurements in cm (before treatment, without egg)

	Cup #1	Cup #2	Cup #3
Solution:	water only	syrup
Height (cm)

Part 2 Results

a. Record below the change in the physical characteristics of the eggs and solutions after they were immersed in their respective experimental solutions for 24 hours. Be careful the eggs are fragile and slippery.

b. Record the height of the experimental solutions after treating the eggs for 24 hours and after removing the eggs from their respective solutions.

Table 2.1 Solution height measurement in cm (after treatment, without egg)

	Cup #1	Cup #2	Cup #3
Solution:	water only	syrup
Height (cm)

c. Record below the measurements of the eggs after they were immersed in their respective experimental solutions for 24 hours. Be sure to note what kind of solution was prepared for Egg C and include this datum, when relevant, for the tables following.

Table 2.2 Egg circumference measurements (in cm, after treatment)

	Egg A	Egg B	Egg C
Solution:	water only	syrup
Measurement #1 (cm)
Measurement #2 (cm)
Measurement #3 (cm)

Table 2.3 Egg circumference (after treatment)

	Egg A	Egg B	Egg C
Solution:	water only	syrup
Average value (cm)
Uncertainty (cm)

d. Record below your observations of the eggs’ physical characteristics after you dissect them. This process may be messy so conduct it in a suitable setting.

Analysis (22 points)

a. Compute the change in circumference for each egg by subtracting the average values of the circumference measurements for each in Table 1.2 from the average values for the same egg in Table 2.3. Record the results in the first row of Table 3.1 (below). To reflect on the significance of the changes that you have measured, transcribe the uncertainty in your circumference measurements from Table 2.3 to the second row of Table 3.1 below. Compare the uncertainty in your circumference measurements to the changes in circumference that you observed.

Table 3.1 Egg circumference change compared to measurement uncertainty

	Egg A	Egg B	Egg C
Solution:	water only	syrup
Change in Circumference (Table 2.3- Table 1.2)
Uncertainty in measurement (Table 2.3)

b. Compute the change in solution height for each solution by subtracting the values in Table 1.3 from those in Table 2.1 and recording the result in Table 3.2 (below)

Table 3.2 Solution height changes (before versus after treatment)

	Cup #1	Cup #2	Cup #3
Solution:	water only	syrup
Change in Height (Table 2.1 –Table 1.3)

c. Write an analysis of 3 or more paragraphs of your results, and do the following:

· Describe and explain your results. How do they relate to the phenomenon of osmosis? (You may need to conduct additional independent research and cite your source.)

· State whether you obtained the results you expected and explain why you did or did not get the expected results.

· Describe the utility of the tracking measurement uncertainty. What does it allow you to do? Why is estimating the uncertainty in measurements an important part of scientific experiments.

· Summarize the overall knowledge you gained from this Lab. How do you think your results might apply to cells generally?

Conclusion (3 points)

a. Write a 1-paragraph conclusion that includes a brief recap of the main points in your analysis.

b. Propose an osmosis-related question that would be interesting to research further.