Diffusion Rate

Introduction

• Diffusion rate shows how fast the process of diffusion take place.

• The net migration of particles from a region of high concentration to one of low concentration is referred to as diffusion, which is a physical phenomenon. Diffusing substances might be solids, liquids, or gases.

• Similar to this, any of the three physical states could potentially be present in the medium where diffusion takes place. The airborne movement of ammonia gas serves as an illustration of this. Similar to how nitrogen gas would swiftly diffuse into the atmosphere if a liquid nitrogen canister had a small leak.

What is Diffusion?

Diffusion is a phenomenon that results in the movement of molecules of substance from a high-concentration area to a low-concentration area. It happens when molecules move randomly. An illustration of how liquid and gas particles migrate from a high concentration to a low concentration is shown below.

Fig: Diffusion

Types of Diffusion

Diffusion is of two types. They are explained below −

Simple diffusion

• Simple diffusion is just the migration of molecules along their concentration gradient when no additional molecules are directly involved. It may entail the movement of a particle over a membrane or the dispersion of a substance through a medium.

• Diffusion occurs over a lipid bilayer-based semi-permeable membrane in the majority of biological systems is an example of simple diffusion. Specific molecules can pass through the membrane's pores and holes.

Facilitated diffusion

• In contrast, facilitated diffusion, as the name suggests, necessitates the presence of a second molecule for diffusion to take place. Large or polar molecules must be transported through the hydrophobic lipid bilayer via facilitated diffusion.

• All cell's biochemical functions depend on facilitated diffusion since there is a constant connection between the numerous subcellular compartments.

• For instance, compared to a sodium ion that is almost identical in size and charge but has a considerably higher affinity for the channel protein that transports potassium ions.

Factors affecting Diffusion

The rate and extent of diffusion can be changed by any one of the factors given below.

Temperature

• Molecules move with a given amount of kinetic energy in every system. It can seem random and is typically not oriented in any particular way. These molecules change their direction of motion as well as their momentum and velocity when they encounter one another.

• All particles in the system have an increase in kinetic energy as the temperature rises. As a result, collisions and the pace at which solvent and solute molecules travel both increases.

Area of interaction

• If dry ice is split into several pieces, the area that interacts with the atmosphere rapidly grows. Within dry ice, fewer molecules only come into contact with other carbon dioxide particles. As a result, the rate at which the gas diffuses into the air likewise increases.

• For instance, purple vapours start to form and mix with air when iodine is sublimated over a hot burner. When sublimation is done in a small crucible, the fumes slowly travel towards the container's opening before quickly dissipating. The rate of diffusion stays low even though they are constrained to the crucible limited surface area.

The steepness of the concentration Gradient

It follows that the likelihood of a molecule diffusing away from the centre area is higher when the medium has a very low concentration of the solute. This is so because the likelihood of molecules leaving a region with higher saturation is what largely drives diffusion.

Particle Size

• A smaller particle will diffuse more quickly than a larger-sized molecule at any given temperature. This has to do with both the molecule's mass and surface area.

• Smaller, lighter particles will diffuse more quickly than bigger, heavier molecules because of their smaller surface areas.

• As an illustration, both carbon dioxide and oxygen gas diffuse slightly more quickly than iodine gas, yet both gases travel more swiftly than iodine gas.

Examples of Diffusion

• Without needing to be stirred, sugar dissolves evenly and sweetens the water.

• The incense stick is lit, and as it burns, smoke fills the space as it is released into the air.

• The water diffuses when boiling water is added to the dry noodles, rehydrating them and giving them a plumper, more saturated appearance.

Causes of Diffusion

Diffusion is a physical and natural process that occurs without shaking or agitating the liquids. Diffusion occurs in gases and liquids because random molecular movement is possible. The molecules run into one other and move in different direction.

Significance of Diffusion

The various life processes all entail the crucial mechanism of diffusion. It is the net movement of particles, ions, molecules, solutions, etc., as was already mentioned. Diffusion is crucial to the movement of molecules in all living things as they are metabolized by cells.

The following are some reasons why diffusion is significant −

• As part of the respiration process, this technique helps release carbon dioxide gas into the blood through the cell membrane.

• Diffusion also occurs in plant cells. All green plants receive water from the earth through the root hair cells.

• Ion transfer across neurons that results in an electrical charge is caused by diffusion.

Conclusion

• Diffusion is a physical phenomenon which has a wide range of applications, which cause the transfer of particles or molecules from a high to a low concentration gradient.

• Spreading of smell, dissolving solids in liquids and blood flow, all these work under the principle of diffusion. Factors like temperature, area of interaction and particle size, and concentration gradient govern the diffusion rate.

FAQs

1. What is osmosis?

It involves the passage of solvent molecules via a semipermeable membrane from an area of lower concentration to a region of higher concentration. Since water serves as the solvent for all living things, osmosis is understood by biologists to be the diffusion of water over a membrane with selective permeability. Osmosis, for instance, is used by plants to extract water and minerals from their roots.

2. Is dialysis a diffusion process?

Yes, it is the movement of solutes through a membrane with a certain permeability. A membrane is said to be selectively permeable if it only permits a limited number of ions and molecules to flow through while preventing the passage of others.

3. What is the meaning of the word diffusion?

The Latin term diffundere, which means “to spread out,” is the root of the English word diffusion.

4. Why is the diffusion of gases faster than liquids?

Because gas particles move very swiftly in all directions while liquid particles move slowly in comparison to gas particles, diffusion happens more quickly in gases than in a liquid.

5. What is Graham’s law?

Graham's law states that the square root of the molar mass of a given gas is inversely proportional to the rate of effusion or diffusion of that gas.