How is equilibrium reached in diffusion

From Wikipedia The diffusion continues until the colour is evenly distributed. At this point, the process is at equilibrium. Diffusion across a membrane A substance may be present in unequal concentrations on either side of a cell membrane, as shown in the left-hand side of the figure below. At that point, equilibrium is reached. Related questions How does temperature affect dynamic equilibrium? Why is dynamic equilibrium important for living organisms? What is dynamic equilibrium?

What are some common mistakes students make with dynamic equilibrium? A distinguishing feature of diffusion is that it results in mixing or mass transport without requiring bulk motion. Thus, diffusion should not be confused with convection or advection, which are other transport mechanisms that use bulk motion to move particles from one place to another. Diffusion : Particles moving from areas of high concentration to areas of low concentration. Molecular diffusion, often called simply diffusion, is the thermal motion of all liquid or gas particles at temperatures above absolute zero.

The rate of this movement is a function of temperature, viscosity of the fluid and the size mass of the particles. The mixture of a solute in a solvent is called a solution. Just like the first cup, the sugar is the solute, and the water is the solvent. But now you have two mixtures of different solute concentrations. In comparing two solutions of unequal solute concentration, the solution with the higher solute concentration is hypertonic , and the solution with the lower solute concentration is hypotonic.

Solutions of equal solute concentration are isotonic. The first sugar solution is hypotonic to the second solution. The second sugar solution is hypertonic to the first. You now add the two solutions to a beaker that has been divided by a semipermeable membrane, with pores that are too small for the sugar molecules to pass through, but are big enough for the water molecules to pass through. The hypertonic solution is one one side of the membrane and the hypotonic solution on the other.

The hypertonic solution has a lower water concentration than the hypotonic solution, so a concentration gradient of water now exists across the membrane. Water molecules will move from the side of higher water concentration to the side of lower concentration until both solutions are isotonic.

At this point, equilibrium is reached. Red blood cells behave the same way see figure below. When red blood cells are in a hypertonic higher concentration solution, water flows out of the cell faster than it comes in. This results in crenation shriveling of the blood cell. On the other extreme, a red blood cell that is hypotonic lower concentration outside the cell will result in more water flowing into the cell than out. This results in swelling of the cell and potential hemolysis bursting of the cell.

In an isotonic solution, the flow of water in and out of the cell is happening at the same rate. Osmosis is the diffusion of water molecules across a semipermeable membrane from an area of lower concentration solution i. Water moves into and out of cells by osmosis. A red blood cell will swell and undergo hemolysis burst when placed in a hypotonic solution. When placed in a hypertonic solution, a red blood cell will lose water and undergo crenation shrivel. Animal cells tend to do best in an isotonic environment, where the flow of water in and out of the cell is occurring at equal rates.

If the substance can cross the cell membrane, its particles will tend to move toward the area where it is less concentrated until equilibrium is reached. At that point, the concentration of the substance on both sides of the cell membrane will be the same. Because diffusion depends upon random particle movements, substances diffuse across membranes without requiring the cell to use energy. Even when equilibrium is reached, particles of a solution will continue to move across the membrane in both directions.

However, because almost equal numbers of particles move in each direction, there is no further change in concentration.

Equilibrium is reached in a system when the concentration of a solute is Look at the beaker on the left in the figure at right. There are more sugar molecules on the left side of the selectively permeable membrane than on the right side. That means that the concentration of water is lower on the left than it is on the right. The membrane is permeable to water but not to sugar. This means that water can cross the membrane in both directions, but sugar cannot.

As a result, there is a net movement of water from the area of high concentration to the area of low concentration. Water will tend to move across the membrane to the left until equilibrium is reached. At that point, the concentrations of water and sugar will be the same on both sides of the membrane. For organisms to survive, they must have a way to balance the intake and loss of water. Osmosis exerts a pressure known as osmotic pressure on the hypertonic side of a selectively permeable membrane.

Osmotic pressure can cause serious problems for a cell. Because the cell is filled with salts, sugars, proteins, and other molecules, it will almost always be hypertonic to fresh water. This means that osmotic pressure should produce a net movement of water into a typical cell that is surrounded by fresh water.

If that happens, the volume of a cell will increase until the cell becomes swollen. Eventually, the cell may burst like an overinflated balloon. Fortunately, cells in large organisms are not in danger of bursting.

Most cells in such organisms do not come in contact with fresh water. Instead, the cells are bathed in fluids, such as blood, that are isotonic. These isotonic fluids have concentrations of dissolved materials roughly equal to those in the cells themselves. Other cells, such as plant cells and bacteria, which do come into contact with fresh water, are surrounded by tough cell walls.

The cell walls prevent the cells from expanding, even under tremendous osmotic pressure. However, the increased osmotic pressure makes the cells extremely vulnerable to injuries to their cell walls.

Which plant and bacterial cell structure protects the cells from damage from osmotic pressure? Facilitated diffusion does not require the cell to use energy because