Diffusion and concentration

Introduction

Diffusion and concentration process are fascinating phenomenon in the science field. It is a visible process in the physical world. The study of diffusion processes started in the 19th century. The spreading of the fragrance of flowers is the best-known example of this process. This process involves the random movement of substances such as atoms, ions, molecules, etc. from a region of higher concentration to a lower concentration. It always requires a concentration gradient that is a difference in concentration. The number of particles present in the total volume or a given volume is the concentration. For a given substance, if there is a difference in concentration, it is defined as the concentration gradient.

What is Diffusion?

The process that involves the movement of particles or substances from a region of higher concentration to a lower concentration is diffusion. That is, the random motion of particles will take place from the more concentrated region to the less concentrated region. A concentration gradient is always essential to show the diffusion process. The phenomenon of transfer of particles will remain until there is no difference in concentration between the systems or the concentration gradient becomes zero. The rate of diffusion depends directly on the concentration gradient.

In solids, liquids, and gases, the molecules present in them are in constant motion because of the kinetic energy present in these molecules. And during these motions, the molecules also undergo collisions with each other. The collision of molecules makes the molecules move in random directions. This collision is responsible for propelling out molecules to a less concentrated area. That is why the transfer of molecules is always from a more concentrated region to a less concentrated region. And after the completion of diffusion, the unequally distributed molecules become uniformly distributed and thus form a dynamic equilibrium. The name dynamic equilibrium is given because the molecules are still in motion, but there is no change in concentration.

Types of Diffusion

There are two types of diffusion, simple and facilitated diffusion. They are explained in detail below.

• Simple diffusion − The diffusion process that doesn't involve the use of any other molecules. It simply involves the transfer of molecules from a highly concentrated region to a less concentrated region. It is mainly present in biological systems that involve the transfer of particles in and out of the cells.

• Facilitated diffusion − The type of diffusion process that needs the presence of a facilitator or an external molecule to make the diffusion process. It requires the use of a carrier that can carry a particular substance. It is especially essential for the movement of larger and polar molecules. This is faster than simple diffusion.

Factors affecting Diffusion

The process of diffusion is affected by certain external factors too. Some of the factors that impact the rate of diffusion are explained below.

• Temperature − When the temperature is increased, the kinetic energy of molecules will also increase and so the collision between molecules will also increase. The increased kinetic energy thereby increases the propelling out of molecules to a less concentrated region. That is, increased temperature will increase the rate of diffusion too.

• Particle size − The particle size will also have an effect on the rate of diffusion at a given temperature. The diffusion will be high when the particle size is smaller. The diffusion of oxygen gas is faster than iodine gas.

• Surface area − As the surface area of particles increases, the process of diffusion will also increase.

• Concentration gradient − When the difference between the concentration of two regions is high, the rate of diffusion will also be high.

Examples of Diffusion

Some examples of diffusion in the physical world are pointed out below.

• The spreading of fragrance or smell of perfumes, incense sticks, food, etc.

• Making tea with the help of tea bags.

• The opening of soda water involves the spreading of carbon dioxide.

• Air pollution results from the spread of small dust particles.

• Food colouring is an example of diffusion.

• The entering of oxygen into the bloodstream during breathing is an example of diffusion.

• The human body needs water for many processes, and the diffusion of water is responsible for this.

Causes of Diffusion

Diffusion is a natural process that is caused by the transfer of molecules from a region of higher concentration to a low concentration. It doesn't need any shaking or mixing of solutions. Molecules present in gas, solid, and liquid also participate in the process of diffusion. The random motion of molecules is a cause of the diffusion process.

Significance of Diffusion

Diffusion plays an important role in our daily life activities.

• The process of diffusion has a major role in the biological system, which helps in the transfer of molecules in and out of the cells of the human body.

• The diffusion process is responsible for the intake of water by plants from the soil.

• The smell of certain gases is very significant and that helps in the prevention of certain accidents in the chemical industries.

• The exchange of respiratory gases is also an effect of the diffusion process.

Conclusion

Diffusion is a significant phenomenon with many applications in the biological, physical, and chemical fields. The process involves the transfer or movement of particles from a region of higher concentration to a region that is less concentrated. Certain external factors can affect the rate of diffusion. They are temperature, particle size, concentration gradient, surface area, etc. There are mainly two types of diffusion, simple and facilitated diffusion. Simple diffusion doesn't need any external molecule to facilitate the process, while facilitated diffusion needs the use of a facilitator to make the diffusion process. It is mainly for large-sized molecules. There exist many applications for diffusion such as the spread of fragrance, respiratory gases transport, water transport over the body, particle transport in and out of cells, etc.

FAQs

1. What is osmosis?

It is a special category of diffusion that involves the transfer of water from a region that has a high-water concentration to a region that has less water concentration through a semipermeable membrane. Semi-permeable membranes are thin layers that allow the passage of small particles.

2. How does distance affect diffusion?

When the distance between two regions is in a moderate range, the process of diffusion will take place faster and is because of the reason that molecules do not need to travel long distances to get diffused.

3. Which cell shape is best for diffusion?

The rate of diffusion will be faster when cells have a spherical shape because it has more surface area.

4. Does diffusion require a membrane?

Diffusion doesn't require the use of a semi-permeable membrane, only a concentration gradient is required.

5. What is the effect of entropy during diffusion?

Diffusion is a spontaneous process, so the process of diffusion increases the entropy too. While it decreases the Gibbs free energy.