Osmometer: An Introduction
An osmometer is an apparatus used for measuring the osmotic power of a solution, colloid, or compound. It’s an instrument used for measuring osmotic pressure. It calculates osmotic concentration on a scale of milliosmoles per unit of weight. It provides us with the osmotic strength and pressure of various colloidal systems.
What is an Osmometer?
An osmometer measures the osmotic strength of a solution, colloid, or compound.
Several different osmometers are deployed:
Vapour pressure osmometers: They determine the osmotically active particles that degenerate the vapour pressure of the solution.
Membrane osmometer: It measures the osmotic pressure of a solution's separation from pure solvent by a semipermeable membrane.
Freezing point depression osmometer: They determine the osmotic strength as osmotically active compounds depress the freezing point of the solution.
Osmometer Principle
A potato osmometer is used to define the process of osmosis in living plant cells. In a potato osmometer, the water moves into the cells through the semipermeable membrane. It works on a principle of the movement of water or solvent from a higher potential region to a lower potential region where it's separated by a semipermeable membrane, so the molecules progress from the pure state to the concentrated state.
Potato Osmometer
Also known as potato osmoscope, it is used to determine the process of osmosis in living plant cells. In this osmometer, water from surrounding areas moves into the cells of the potato plant through a semipermeable membrane. Then water moves from cell to cell from a region of higher concentration to a region of lower concentration. The potato osmometer demonstrates the process of osmosis in a potato plant effectively where transportation of nutrients and discharge of metabolic wastes occur along with the maintaining of intracellular fluid level in the plant.
Osmosis in Potato
Osmosis is a process in which solvent molecules move through a semipermeable membrane from a region of higher concentration to a region of lower water concentration. The fluid that moves through the membrane is the solvent, and solute is the dissolved particles present in it. Osmosis in potatoes happens when water moves from a region of less concentration. When a potato is placed in salt water, the water inside the potato moves out by osmosis.
Permeability in Potato Osmoscope
Permeability is the state of a substance to allow the passage or movement of molecules through it. Since the potato tissue is impermeable to sugars and sodium ions, it is permeable in salt solution because there is a higher concentration of water molecules inside the tissue than outside it.
The cytoplasm of tuber cells acts as a semipermeable membrane, and a water gradient develops between the sugar solution in the osmoscope and the external water, thus, allowing water to enter the sugar solution causing the level to rise to prove the membrane of a living cell in the potato osmoscope is selectively permeable in nature.
Potato Osmometer Diagram
The sugar solution is osmotically active, and the cells of the tuber act as a semipermeable membrane, thus enabling water to enter the sugar solution through the process of osmosis.
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Potato Osmometer Experiment
Interesting Fact
An interesting fact is that the living cells of the potato demonstrate that water enters through the semipermeable membrane where the potato acts as an osmometer.
Important Questions
1. Is the usage of potatoes to prepare an osmoscope justified?
Ans. Potato is peeled on one side and completely flattened on the other and then placed in water in the petri dish that one side serves as the base, the water entering into the sugar solution through the tissues of the potato, which has a selective permeability in its membrane, it's important that the potato is peeled and not kept as it is. Potatoes are full of water and starch and will gain water when immersed in any solution and lose water in a concentrated solution, making them an ideal choice for usage as an osmoscope.
2. Compare the effect of osmosis in potato cells in solutions with different temperatures.
Ans. For observation of potato cells in solutions at different temperatures, we prepare two solutions in two Petri dishes with one cup of water and 2 tsp salt. We heat both solutions for 30 to 45 seconds until we see it's warm enough. We observe temperature rising and the osmosis rate gets faster because water molecules move quicker, crossing the membrane of the potato. The higher the temperature, the faster the water molecules move. The temperature not only influences the osmotic pressure but is directly proportional to the concentration of the solution.
Key Features of Study of Osmosis by Potato Osmometer
The potato tuber acts as an osmometer.
The living cells of potatoes demonstrate that water enters through the semi-selectively permeable membrane.
An osmometer measures the osmotic strength of a solution, colloid, or compound.
FAQs on Study of Osmosis by Potato Osmometer
1. Define reverse osmosis.
Reverse osmosis is a water purification process which employs a partially permeable membrane which removes ions and unwanted molecules from our drinking water. Reverse osmosis uses an applied pressure to override the osmotic pressure. This process removes different types of chemical and biological particles suspended in water. The water filtered after reverse osmosis is safe to drink as the contaminants are removed through the process, which may have a detrimental health issues.
2. What if a boiled potato is used instead of a raw potato in the potato osmometer experiment?
A boiled potato does not have living cells, and the process of osmosis cannot happen in it. The cells of a boiled potato are dead after being cooked at high temperatures, and the cell membrane is not viable either, so no osmosis or water movement can occur. Osmosis only occurs in a raw potato because of its living cells and cell membrane. When the potato is boiled, the cell wall breaks down, and carbohydrate content also breaks down, heralding a chemical change.
3. On the contrary, if a potato is placed in salt water, then what do we observe then?
If salt’s concentrated solution has a high gradient level, water moves out of the potato into the petri dish, thus leading to the shrinkage of potato cells. The salt solution has a high concentration of salt, and the water present in the petri dish has a low concentration of water as compared to the concentration of water inside the potato cells. So this will result in loss of water from the living cells of the potato, thus, making it plasmolysed and shrinkage.
