Demonstration of Osmosis process by Thistle Funnel Method


Osmosis is a physical phenomenon which occurs in all living organisms where movement of water molecules occurs between the cells or shifting of water occur from one cell to the other through a semi-permeable membrane. In this article I gave simple experiment through which osmosis process can be demonstrated. I gave some important questions as well as answers related to the experiment which will be useful for those preparing for final practical or theory exams of various Boards.

Introduction

Osmosis is a physical phenomenon in which water or solvent molecules move from dilute solution to a concentrated solution where both the solutions are separated by a semi-permeable membrane. In other words osmosis also can be defined as the movement of water molecules from its (water) higher concentration to its lower concentration through a semi-permeable membrane. In osmosis process movement of water molecules only occur between two deferentially concentrated solutions separated by a semi-permeable membrane. In plants or animals the cell membrane which separate two cells acts as semi-permeable membranes. Cell membrane or plasma membrane of plant cells and animal cells, egg's membrane, Goat's bladder membrane are the natural substance which act as semi-permeable membrane. Cellophane paper, Parchment paper, Viskins bag are the substances which act as semi-permeable membrane are artificial in nature.

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Aim of the Experiment

To demonstrate Osmosis process by Thistle funnel and egg's membrane.

Requirements:-

Beaker, Water, Sugar solution, Egg's membrane, an iron stand.
Demonstration of osmosis process
Demonstration of Osmosis process-(A) Experimental Setup and (B) Control Setup

Procedure for the experiment

A wide mouthed thistle funnel with a narrow long stem was taken. Then an egg's membrane collected from an egg is tied tightly around the wide mouth of the funnel with the help of a thread or rubber band. Now dilute sugar solution is carefully poured into the stem of the funnel to a certain level. The wide mouth of the funnel containing sugar solution is now kept in a beaker with the help of an Iron stand. Now three fourths of the beaker is filled with plain water. A similar control setup also arranged but by taking plain water in the beaker and also plain water in Thistle Funnel. The apparatus are left undisturbed for 10 minutes and we observe the changes in the experimental setup as well as in control setup.

Result

After few hours we find the level of sugar solution increases from its initial level in the experimental setup while there is no change in the level of water in the stem of Thistle Funnel in the control setup. This observation clearly indicates the movement of water molecules occurred from the beaker into Thistle Funnel in the case of experimental setup while in the control setup that there is no movement of water molecules from beaker into Thistle Funnel through egg's membrane because both the solutions are of same concentration.

Precautions:-

  1. The egg's membrane has to be tightly fastened to the mouth of the funnel.
  2. The initial level of sugar solution in the thistle funnel should be carefully noted.

Questions and answers related to the experiment


  1. What is the process demonstrated with the above experimental setup and define it?
  2. Ans. The phenomenon demonstrated in the above experimental setup is osmosis. Osmosis can be defined as the movement of water molecules from a dilute solution to a concentrated solution through a semi-permeable membrane.
  3. What would you observe in the experimental setup after an hour or so? Explain the change observed.
    Ans. There will be increase in the level of sugar solution in the stem of the Thistle Funnel because water molecules from beaker entered into it through the egg's membrane which is a semi-permeable membrane.

  4. Here is an experiment on Experiment on Transpiration in plants with dicot leaves
  5. Why a control setup was used for this experiment?
    Ans. By using a control setup we can clearly prove through that in osmosis process water molecules are only moving from a dilute solution to a concentrated solution through a semi-permeable membrane.

  6. Keeping in mind the root hair cell and its surroundings, name the parts that corresponds to concentrated sugar solution (1), egg's membrane paper (2), and water (3) in the beaker.
    Ans.
    1. Concentrated sugar solution in the Thistle Funnel corresponds to cell sap of root hair cell
    2. Egg's membrane corresponds to cell membrane of root hair cell
    3. Water in the beaker corresponds to soil solution.
  7. Name any other substance that can be used instead of egg's membrane in the above experiment?
    Ans. Parchment paper, Cellophane paper, Goat's bladder membrane.

  8. What is the nature of egg's membrane used in the above experiment?
    Ans. Egg's membrane acts as a semi-permeable membrane in the above experiment. A semi-permeable membrane is a membrane which allows smaller particles like water molecules through it but prevents the movement of larger particles like sugar or salt particles.

  9. Name the two conditions required for osmosis to occur in the above experimental setup?
    Ans.
    1. Presence of semi-permeable membrane (Egg's membrane)
    2. Different concentration of solutions in Thistle Funnel and Beaker

  10. What is the tonocity of the solution kept in the Thistle funnel of experimental setup and control setup? Define them.
    Ans. The tonocity of solution kept in the Thistle funnel of experimental setup is Hypertonic solution. A solution which is more concentrated in nature when compared to the surrounding solution is known as Hypertonic solution.

    The tonocity of solution kept in the Thistle funnel of control setup is Isotonic solution. A solution which is equal in concentration with surrounding solution is known as Isotonic solution.

  11. Here is an experiment on How to measure the rate of transpiration of a cut twig with Ganong's Potometer
  12. Give three significance of osmosis in living beings.
    Ans.
    1. Osmosis play an important role in the absorption of water by the roots of the plants from soil.

    2. Osmosis regulates the opening and closing of stomata.

    3. Osmosis maintains osmotic balance i.e. osmoregulation in animals.

    Here is a video of Osmosis experiment:-

    Courtesy:- Youtube.com


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