Planning a:
Introduction / Background Info:
a) must reflect what your lab is about
b) introduce and describe key terms and concepts, but write in story form rather than as a list of words and definitions.
diffusion, osmosis, isotonic, hypertonic, hypotonic
c) information pertinent to the investigation (analysis of ingredients in the drinks tested, identifying what liquids would be hypertonic, hypotonic or isotonic to the cells)
Question
Something along the lines of "How the IV affects the DV....."
Hypothesis
Write hypothesis so there is a definite answer and an explanation of why your hypothesis would occur. (The reasoning for the hypothesis could be listed in the introduction.)
Rank the different liquids according to how much mass gain or loss will occur.
Example:
"Cells placed in water will gain the most mass. Water hydrates better than the other tested drinks because it is hypotonic to the cell solution. This creates a situation where there is more water outside the cell than in its cytoplasm, so water diffuses into the cell and the cell gains mass. The other drinks contain solutes, so they will not cause the cells tested to gain as much mass" Powerade will lose mass because...... Gatorade will lose the most mass because.........etc.
Variables:
a) Identify the Independent and dependent (measured) variables. Independent (drinks or solutions tested). Independent - Change (%) in mass of veggie pieces studied.
b) Identify key variables which need to be maintained constant.
i) calibrate balance, and wipe off any excess moisture.
ii) consistently dry potato or veggie pieces before each weighing.
iii) use large amounts of potato or veggie pieces to reduce errors from each weighing.
iv) Variables affecting rate of osmosis: temp, pressure, time, size and shape of veggie pieces. (Time periods of a day or more allow complete osmosis to occur and variations of 10-15 minutes between samples at that length of time would have limited influence on results.)
Materials: most students received a complete (c) score on this, but some forgot to list key materials like the balance.
Design: Many students neglected to list quantities of materials used, length of time, and the pre-blotting step to dry veggies before the 1st weighin. Many did not use enough veggie pieces.
Sufficiency: # of trials. most received a complete (c) if they tested a number of solutions and performed 3 or more trials.
Raw Data = the original, unmanipulated data that was collected)
Displays raw data (that was collected in a table with all columns labelled (units included) and a descriptive title (See your hypothesis!)
Some students left off the title or did not include the raw data!
Data Manipulation:
a) Student uses averaging, calculates % change where needed, and calculates standard deviation correctly. Explain why some data manipulations were made (like need to convert results to % change, ect.)
b) Show an example of the equation for each manipulation used, and one example of how to use the equation to find the result is a nice addition.
c) Display manipulated data in table form with title and all labels. (This may be the same title as that used for the raw data.)
d) Some students did a good job explaining how they used the differences between the averged results along with the standard deviations of the different solutions tested to validate their experiment. Many others did not do this, or interpreted their results wrong! Some of you did this as part of your conclusion, which was ok.
e) Graphs the final results.
i) Graphs should show averaged trial data for each parameter tested (type of drink or sugar or salt solution tested).
ii) Where possible, try to represent the standard deviation for each liquid tested too!
iii) The X- and Y- regions of the graph should be labelled with appropriate units.
iv) A descriptive title should be used (See hypothesis). IV vs DV is probably not fully adequate.
iv) Use a key to identify drinks if needed.
v) Uses the correct graph form to clearly demonstrate results. Bar Graphs for comparing drinks or solutions, or a line graph if you were trying to find out how much water the veggie piece originally had!
Conclusion:
a) Restate your hypothesis to compare to results.
b) State general trends (rank the drinks or solutions) and then list specific averaged results. The averaged results should include the units and the standard deviation of the trials!
c) State which results agree with the hypothesis, and which ones don't. (Be aware that you have not "proved" anything here! Results agree or disagree with the hypothesis or suggest trends.)
d) Explain the results. (Example: Water caused the veggie pieces to gain the most mass because there was little solute in the water, so it was hypotonic to the veggie pieces. Water diffused into the veggie cells and they gained mass. Gatorade was hypertonic to the veggie pieces, so water diffused out of the veggies and they lost mass.......etc...
e) If the standard deviations support your conclusions, state so...(See data manipulation above. This would only need to be done once, somewhere....)
Analysis of experiment and suggestions to improve the design:
a) Identifies key variables that needed to be controlled. (increased mass of original veggie pieces, blotting the pieces consistently before each weigh-in, keeping the balance clean and dry, cutting veggie pieces to same size and shape (not too thick!), # of trials, # of solutions tested, use of more accurate measuring devices, etc....
b) Suggests specific design steps to improve upon these problems. List specific number of trials, amounts of materials useds, and how it would be done. You could also just list a whole new design here too!