Transcript hypertonic solution

Using the Scientific Method.
Investigating Osmosis in Potato
Cells.
AIM: to find out what happens to samples of
potato when they are placed in a hypertonic
solution.
Osmosis…what does it mean again?
Osmosis is the special diffusion of water
from high water concentration to low water
concentration through a selectively
permeable membrane.
Plant Cells and Osmosis
Hypotonic solution: more
water outside of the cell than
inside, therefore water will move
into the cell by osmosis. This
causes the cell to swell and
become turgid
Hypertonic solution: more
water inside the cell than
outside, therefore water will
move out of the cell by osmosis.
This causes the cell to become
softer or flaccid
Hypothesis
Since water moves from a HWC to a LWC, water
will move out of the potato cells by osmosis in
a hypertonic solution.
Apparatus Required
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Safety goggles
Two beakers
Potato samples
Cork borer
Hypertonic solution
Stop clock
Measuring scales
Paper towel
Labels
Method (Experimental procedure)
Beaker A containing
50ml of water
Beaker B containing
50ml of hypertonic
solution
Potato cell samples
Results table
• Copy and complete:
Mass at 0 minutes (g) Mass at 30 minutes (g)
Difference (+/-)
Beaker A
(water)
Beaker B
(hypertonic solution)
Your teacher may ask you to enter your results into a table, recording
everyone's results in order to gain an average set of results.
Method (Experimental procedure)
1.
Collect a cork borer and cut out two samples of potato.
2.
Roll the potato samples in paper towel to dry off any excess water
and measure mass separately.
3.
Record your initial results in your results table.
4.
Place each sample in a different beaker marked A or B.
5.
Cover the potato samples in beaker A with 50ml of water and potato
sample in beaker B with 50ml of hypertonic solution.
6.
After 30 minutes, remove samples from beakers, dry off with fresh
paper towel and re-measure mass of each piece of potato.
7.
Record final results in your table.
Variables
• In all scientific investigations, there are a number of
variables.
• The independent variable
– What factors you will manipulate to test your hypothesis.
• The dependent variable
– What is changed / measured in the experiment.
• The control
– What you will keep the same in both experiments for a fair
comparison.
What are the independent, dependent and controlled in this
experiment?
Analysis of results
• Using the data from your completed results table,
draw a bar graph to show the mass of the potato
cylinders in both solutions at 0 minutes and 30
minutes.
• Repeat this process for the class average data for
both solutions at 0 minutes and 30 minutes.
• Use a pencil and ruler to draw your graph!
Reliability
• All experiments are repeated several times
and an average calculated.
• This is very important in science so that a
reliable set of results are obtained.
• Why do you think repeating and averaging
increases reliability of results?
Conclusion
• The aim of this scientific investigation was to
find out what happens to samples of potato
when they are placed in a hypertonic solution.
• Did your hypothesis match what you found
out? If not, why not?