Content Objective: To determine the isotonic point of a potato by measuring the percent change in mass and to explain osmosis using the terms isotonic, hypertonic and hypotonic

Language Objective:  Create an IA that includes data collection, analysis, conclusion and evaluation.

Instructions

Research Question: How does changing the concentration of sodium chloride, ranging from 0 to 1 M, affect the percentage change in the mass of Solanum tuberosum cylinders immersed in their respective solutions for 25 minutes?

Method

Equipment:

Potatoes

Scale accurate to 3 decimal places

Cork borers

200 mL Sodium Chloride solutions of 0, 0.125, 0.25, 0.5, 0.625, 1.0

Paper Towels

Knife

Potatoes

Ruler 

Laboratory Instructions

1. You are supplied with one of six molarities of NaCl (0M, 0.125M, 0.25M, 0.5M, 0.625M or 1.0M).

2. You need to cut and measure 5 potato cylinders that have a length of 2 cm and a diameter 1.6 cm for your molarity.  

3. Weigh and record each cylinders and record the mass (in grams). Record your observations (qualitative) of the appearance of the potato cylinders. (color, texture, etc).

4. Place potato cylinders in your solution.

5. After 25 minutes, dry and reweigh each of the potato cylinders and record the mass (in grams). Record your observations (qualitative) of the appearance of the potato cylinders and record them here.

Data Processing 

6.     Start with this template

7. Create a table of raw data.

8. Calculate the percent change for each trial. 

(Final value - Initial  value)/(initial value) * 100

9.     Include a sample calculation for percent change.

10. Graph the concentration of the NaCl solutions versus the percent change in mass.

11.    Include a statistical analysis

12. Write an analysis and conclusion.

13. Write an evaluation 

Data

Resources

Two Examples 

Example 1
Example 2 

Background on Osmosis
Notes

Analysis

This is the process of making sense of the data that will then lead into a conclusion. Evidence includes; the explanation of trends, comparisons, correlations, optima, maxima (plateau) or the correct interpretation of the results of statistical calculations. 

• If the data collected and processed does not finally lead to clear patterns or trends then the efforts to make sense of the data objectively will be rewarded. 


• When interpreting a graphical relationship be careful of the thoughtless presenting of the Excel best-fit equation as the outcome finding.

• There is more value in recognising the relationship to be linearly proportional, inversely proportional, exponentially proportional, etc. 


Conclusion 

• A statement or discussion of whether the data answers the RQ should be presented. 

• It should refer back to the RQ and be scientifically justified with comparisons made to properly referenced background material. 


• Tie it back to the real world problem you discussed.

•  It is most likely that the data may go some way to supporting (that’s a good word to use!) a conclusion but will rarely be sufficient to be considered incontrovertible evidence in a school-based investigation. 

• The context needs to be relevant. It may refer to the correct scientific context presented in the background information, or accepted literature values. 

• If there is no accepted value available, the findings need to connect to the relevant scientific context to provide justification the candidate used the scientific context to show or prove that the findings are reliable. 

Evaluation

Weaknesses & Strengths 

• Obvious weaknesses that are consistent with the direction of error should be identified and addressed.

• Consideration of both the strengths and difficulties and the quality of the data and processing is needed. These should not include errors due to sloppy manipulative skills or hypothetical events for which there is no evidence. 

• If you reflect on how your conclusions could be more valid and justified by adapting the method to address underlying factors such as range, sample size, the use of an alternative reaction system to study the same phenomenon, etc., this is considered an evaluation of the methodology.

• High achievement in evaluation will arise in reports where the candidate has a strong understanding of the methodological issues involved in establishing the conclusion.

• The evaluation of the nature of the experimental errors (random or systematic) or weaknesses should be consistent with the findings and not overstated. As part of this process you need to show an understanding of a source of errors relative impact on the reliability of the findings. 

• Your comments on the significance of sources of error must be consistent with the direction of error. 

• If you only addresses practical or procedural issues, by simply giving an account of how their results could be improved by carrying out your stated procedure better, only fulfils the lower band of this descriptor (1-2).

Suggested Improvements & Extensions 

• Both suggested improvements and extensions should be precise, focused and relevant to the investigation. The potential implication of these modifications and how they might bring the experimental results closer to what is expected are discussed. 

• The improvements must be related to the weaknesses identified and they should be feasible in the context of a school environment or field course. 

• The extension suggested should follow on from the research in a meaningful way and show how it will enhance understanding of the topic or RQ. It is clear why knowing this may be important.