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Osmosis Concepts, Applications, and Labs

Osmosis is the movement of water molecules from an area of high concentration to an area of low concentration through a selectively permeable membrane. This helps to balance the concentration of solutes (dissolved substances) on both sides of the membrane. The process occurs naturally and helps cells regulate their water balance and maintain proper function. Osmosis is an important process in biology and is used in many real-world applications, such as in the treatment of dialysis patients and in the preservation of fruits and vegetables.

Cell membranes are selectively permeable and regulate osmosis by controlling the movement of molecules across the membrane. They use proteins to control the size and charge of molecules, allowing some molecules to pass through while blocking others. This allows cells to maintain homeostasis, or a balance of chemicals within the cell, by allowing only certain substances to enter or exit. Osmosis helps create this balance when water moves into and out of the cell based on concentration gradients of solutes inside and outside of the cell.

osmosis and cells
Diagram showing osmosis in plant cell illustration

Osmosis plays an important role in dialysis. During this medical procedure, a semi-permeable membrane is used to separate molecules with different charges and sizes. This membrane allows water to cross over, but it blocks out larger molecules such as proteins. As a result, the concentration of solutes inside the blood gradually increases until it reaches equilibrium with the environment outside of the membrane. This helps cleanse the blood from unwanted substances such as extra salts and toxins, making dialysis an indispensable tool for treating kidney failure.

Osmosis is used in preserving fruits and vegetables by controlling their water content. When fruits and vegetables are stored in a solution with a lower concentration of solutes (such as sugar or salt) than their own tissues, water will move from the tissues into the solution through osmosis. This helps to slow down the decay process by reducing the amount of water available for bacteria and other microbes to grow.

For example, if you want to preserve sliced apples, you can dip them in a solution of sugar and water, which will cause the water in the apples to move into the solution. This reduces the amount of water available for bacteria to grow, which slows down the decay process and helps to preserve the freshness of the apples.

In a similar manner, pickling vegetables such as cucumbers involves soaking them in a solution of vinegar, salt, and spices. The vinegar and salt create an environment that is unfavorable for bacteria and other microbes to grow, which helps to preserve the vegetables for a longer period of time.

Overall, osmosis is an effective tool for preserving fruits and vegetables by controlling their water content and helping to slow down the decay process.

Osmosis is used in water desalination as a process to remove salt and other minerals from seawater to make it suitable for drinking and other purposes. In osmosis-based desalination, seawater is separated from freshwater using a selectively permeable membrane.

The seawater is placed on one side of the membrane, and fresh water is placed on the other side. Osmosis causes the water molecules to move from the side with the high concentration of salt (the seawater) to the side with the low concentration of salt (the fresh water). This creates a flow of water from the seawater to the fresh water, and the salt and other minerals are left behind on the seawater side.

This flow of water can be collected and purified to make it safe for drinking and other purposes. The process can be repeated multiple times to further purify the water and remove more and more of the salt and other minerals.

Overall, osmosis is an effective way to desalinate seawater, making it a valuable tool for addressing the growing need for fresh water in coastal regions and other areas where water is scarce.

Osmosis Lab Pre-Lab

Here is a simple osmosis lab using gummy bears:


  • Gummy bears
  • Distilled water
  • Sugar water (made by dissolving sugar in water)
  • Clear cups or jars (2 for each solution)
  • Ruler or measuring tape


  1. Start by measuring the initial size of the gummy bears using a ruler or measuring tape. Record the size in a table.
  2. Place a gummy bear in each of the two clear cups or jars.
  3. Fill one of the cups with distilled water and the other cup with sugar water. Make sure the water covers the gummy bear completely.
  4. Leave the gummy bears in the solution for at least 30 minutes or until you observe a change in their size.
  5. Remove the gummy bears from the cups and measure their size again. Record the new size in the table.
  6. Compare the initial and final size of the gummy bear in each solution to see the effect of osmosis on the gummy bears.
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Win Elements

I have more than a decade of teaching experience and school leadership at a high school. I co-founded Win Elements LLC to provide two practical tools to solve many school problems and transform the school culture of learning.
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