Biology Controlled Assessment - osmosis in potatoes

this is the low control part of my GCSE Biology Controlled assessment

My experiment was investigating how the mass of the  potato cylinders changed as they were left in different solutions of NaCl. 

Hope it helps & dont forget to rate ;)

HideShow resource information
  • Created by: Rita
  • Created on: 01-04-13 17:07
Preview of Biology Controlled Assessment - osmosis in potatoes

First 337 words of the document:

Biology Controlled Assessment
Introduction
Osmosis is the diffusion of water from a high concentration to a low concentration
through a semi-permeable membrane.
This process does not require energy and is known as passive transport, it works
through pressure to reach equilibrium, i.e. the same concentration on both sides.
There are three main types of solutions in regards to osmosis:
-A hypotonic solution is a solution with a lower concentration of solutes compared
to another. A cell in a hypotonic solution has a higher concentration of solutes than
the surrounding solution, causing water to flow into the cell. Cells can burst (cytolysis)
in some cases.
-A hypertonic solution is a solution with a higher concentration of solutes
compared to another. A cell in a hypertonic solution has a lower concentration of
solutes than its surroundings, leading to a decrease of water in the cell.
-Isotonic solution is a solution that has no difference in solute concentration
across the semi permeable membrane, therefore has no movement of water across
the membrane.
Strategy- S (a)
There are several factors that can control the rate of osmosis:
Temperature - The higher the temperature, the faster the movement of water
molecules across the semi permeable membrane, therefore an increased rate of
osmosis.
Surface area- the greater the surface area of a cell and it's membrane the faster
the rate of osmosis. This is due to the water particles having a larger area of
semi-permeable membrane to pass through, speeding up the rate of osmosis.
Solute Concentration and water potential ()- The higher the concentration
of the solute in a solution, than that of the cell, the faster the rate of osmosis will
occur. Similarly the lower the water potential () of the solution, than that of the cell,
the faster the rate of osmosis will occur.
Factor that I chose:

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

For my experiment I choose solute concentration as my independent variable,
because it's the easiest variable from which to produce reliable, accurate and
reproducible results. I decided not to use temperature as my independent variable
because I believe that it would be more difficult to control and measure than osmotic
gradient.…read more

Page 3

Preview of page 3

Here's a taster:

Test tube rack ­ here isn't a better alternative for the same purpose. My
only principle was that it is easier to keep track of the potatoes when they are
in a rack
18 Test tubes ­ there isn't much difference in the equipment that can be
used to hold the potato cylinders in the solution, however I find getting the
potato cylinders out of a test tube easier than getting them out of a wide
container.…read more

Page 4

Preview of page 4

Here's a taster:

After all the solutions were mixed we labeled them and put them aside. We then
began cutting the potato cylinders. We first set out the cutting tile, onto which we put
the potato. We cut the potato using a core borer, which gave us a perfect potato
cylinder that was identical to the rest.…read more

Page 5

Preview of page 5

Here's a taster:

Strategy ­ S(c)
Before doing our preliminary work, within our group we agreed on a general technique
that we were going to use to do the experiment and use the preliminary work to check
whether the method was good or not and how it could have been improved. In our
preliminary experiments we tested a range of different core borer sizes to see which
one gave us optimal results.…read more

Page 6

Preview of page 6

Page 7

Preview of page 7

Here's a taster:

Range used: - from 0% NaCl concentration (i.e. distilled water) to 5% NaCl
concentration
Change in mass measured: - every 1.…read more

Comments

No comments have yet been made

Similar All resources:

See all All resources »See all resources »