Mr Chips: Investigation to find an isotonic solution for potatoes

Authors Avatar

Mr Chips:

 Investigation to find an isotonic solution for potatoes

Introduction

Investigation aimed to find out the amount of grams of salt solute needed to create an isotonic solution to prevent osmosis in fresh cut potato chips. Osmosis is the movement of water molecules through a selectively-permeable membrane down a water potential gradient. More specifically, it is the movement of water across a selectively permeable membrane from an area of high water potential (low solute concentration) to an area of low water potential (high solute concentration). The water molecules will continue to move through the semi-permeable membrane until both sides have reached a state of equilibrium. Isotonic solution is a solution in which its solute concentration is the same as the solute concentration of another solution with which it is compared

In plant cells when water moves into the vacuole it increases in size and pushes the cell membrane against the cell wall, this causes the cellulose cell wall to stretch slightly and when it can stretch no further it becomes taut and firm. The pressure inside the cell rises and eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. At this point the cell wall prevents the cell from bursting and is said to be fully turgid. Turgidity is very important to plants because this is what provides support to make the green parts of plants stand firm.

When plant cells are placed in highly concentrated solute solutions they lose water through osmosis. Water is drawn from the cell and the vacuole contracts and shrinks drawing the cell membrane away from the cell wall. The effects of the water loss is called plasmolysis and cells in this condition are said to be plasmolysed or flaccid.

When plant cells are placed in a solution which has exactly the same osmotic strength as the cells they are in a state between turgidity and flaccidity and as there is no gradient for the molecules to travel down, equilibrium is set.

To create a fair test certain variables of the experiment need to be considered.  Firstly, the independent variable; this is the only changing factor in the experiment and will be the concentration percentage of Sodium chloride (NaCl) in each dilute solution.

The dependant variable is the factor influenced by the experiment and is a measure of the change in mass of the single potato chips. This will be calculated on a top pan balance and measurements taken before and after the experiment. The mean of each percentage change will be calculated and plotted into a graph to allow the ability to pin point the exact concentration of sodium chloride needed to produce an isotonic solution.

Join now!

The controlled variables are all other aspects of the experiment and need to be kept the same to ensure that the method used will produce fair and accurate results.

These controlled variables include:

  • Amount of solution for each concentration for each boiling tube (25 cm3)
  • Scales used to measure the chips is the same
  • Temperature of the atmosphere in which the investigation takes place, (room temperature) controlled by carrying it out in the same location each time
  • Surface on which the investigation takes place, level bench
  • Length of time in which the chip is submerged in ...

This is a preview of the whole essay

Here's what a teacher thought of this essay

Avatar

This is a well written report on an investigation that has been approached in a good way. 1. Researched information needs to be referenced. 2. The report is missing several subheadings. 3. The analysis needs to use data from the investigation to back up the pattern. 4. The evaluation should suggest further research opportunities. ****