What is Diffusion?
Diffusion can be defined as the procedure involving the net movement of anything like energy, ions, atoms, and molecules normally from a place with a higher concentration to a place with a lower concentration. The driving force behind diffusion is a gradient in chemical potential or Gibbs free energy. Contrary to popular belief, the uphill diffusion of something from a place with a lower concentration to a place with a higher concentration is possible (for instance, in spinodal decomposition).
Diffusion is studied in a variety of fields from economics, sociology, and biology, to chemistry, physics (particle diffusion), and finance (the diffusion of price values, people, and ideas). Despite the little bit of difference in the way they are studied, the central idea of diffusion remains the same i.e., something undergoing diffusion starts from a place with a higher concentration of that said thing under discussion.
A Detailed Example Of Diffusion
Start by collecting some water in a container or a beaker, add a few crystals of copper sulfate to it at one specific region and leave the newly formed concoction like that for some time. Do not disturb it all. Check on the beaker after some time and you will be surprised to see that there will be a uniformly colored solution in that beaker. In this example, you will see that both the crystals of copper sulfate and water diffuse independently. Therefore, you can conclude that a solute in a solution moves from a higher concentration to a lower concentration.
Is There Any Significance of Diffusion?
Yes, there is a great significance of diffusion, it is a part of many important life processes. Since it is the net movement of solutions, ions, particles, molecules, it plays a vital role in the movement of the particles during the metabolic processes happening in the cells.
Other than that, diffusion is significant for the following reasons:
- Diffusion is also involved in the process of respiration as it helps in diffusing the CO2 (Carbon dioxide) out into the blood through the cell membrane.
- The process can also be seen in plant cells as the water present in the soil enters the plant with the help of diffusion through their root hair cells.
- The generation of electrical charge is also a product of diffusion that is responsible for the movement of ions across the neurons that are meant to generate the electrical charge.
What Are The Types of Diffusion?
Let’s move on to the types of diffusion that occur in different materials:
1. Simple Diffusion
Simple diffusion can be defined as just the movement of molecules on the path of their concentration gradient and this happens without the direct involvement of any other substance or molecules. Simple diffusion can either be the spreading of different substances via a medium or the movement of a molecule through a membrane.
Simple diffusion is super important in numerous physical phenomena, chemical reactions, geological events, and can even impact global weather patterns. When it comes to biological systems, simple diffusion occurs through a semipermeable membrane which is made up of lipid bilayer and has openings and pores that allow the easy passage of specific molecules.
2. Facilitated Diffusion
However, facilitated diffusion, as its name shows, needs another molecule which is known as the facilitator to diffuse across something. This kind of diffusion is needed for the movement of polar or large across a hydrophobic lipid bilayer. Another important role of facilitated diffusion is in biochemical processes occurring in every cell as communication occurs between different subcellular organelles.
What is the Disk Diffusion Method?
The disk diffusion method also commonly known as the DDM can be described as an agar diffusion method (also known as ADM). The reason for this is that the plant extract that needs to be tested diffuses from its reservoir via the ADM medium seeded with the concerned test microorganism. The reservoir used is normally a filter paper disk that you place on the top of an agar surface. An inhibition zone forms around the filter paper following incubation oif the plant extracts under testing are microbiologically active. You can calculate the antimicrobial potency of those plant extracts or the isolated compounds you want to test by using the diameter of the inhibition zone.
However, one thing to keep in mind is that the disk diffusion method is not a suitable way of experimentation for lipophilic extracts. The reason for this is that the diffusion of the water-insoluble EO (an example of lipophilic extracts) and its compounds from a filter paper disk into an agar medium is not adequate. And, as a result, the EOs provide negative results or very small inhibition zones are formed with the Disk Diffusion Method as compared to other tests.
What Are Some Examples of Diffusion?
Let’s look at some diffusion in liquids examples along with daily life, human body, and nature:
Examples of Diffusion in Daily Life
As mentioned above, diffusion happens everywhere, it is a universal physical phenomenon. Let’s look at some of its notable examples in our daily lives:
1. Perfume
When you spray perfume, cigarette smoke, air freshener, or any type of strongly scented substance in one part of a room, it slowly reaches other parts of that room because of diffusion.
2. Balloons
Have you ever wondered why helium balloons slowly come back to the ground? The reason for that is the slow diffusion of helium from a region rich in helium (inside the balloon) to a region that is not that concentrated in helium (the outside air).
3. Food Coloring
When you pour a drop of food coloring in water, it spreads throughout the container via diffusion as the molecules gradually spread evenly through water, thus forming one particular shade.
4. Soda
Have you ever noticed that sodas lose their fizz after some time? It happens because of diffusion because the air has a lower concentration of the fizzy CO2 that is present in the soda. As a result, the molecules of the bubbly CO2 leave the soda and disperse into the air.
Examples of Diffusion in The Human Body
As we have established above, diffusion runs the human body as it is responsible for all the important biochemical and biological processes happening in the body.
If diffusion stopped happening in the human body, life would stop as well. Let’s look at some examples of diffusion happening inside the human body:
1. Breathing
The most important process taking place in the human body is directly related to diffusion. When we take a deep breath, the oxygen only enters our bloodstream when the Oxygen (O2) molecules diffuse into deoxygenated blood. The process of breathing in and breathing out is a mechanical action, however, the oxygen only enters the bloodstream via diffusion.
2. Calcium
We do not need calcium just for our bones, we also need it for other physical functions, movement of muscles, and sending nerve signals. When there is inadequate calcium in the bloodstream, the thyroid gland present in the human body secretes a chemical that causes our bones to release calcium. The calcium then diffuses into the blood and solves the issue.
3. Kidneys
Even kidneys display diffusion as they filter dangerous chemicals and substances from the bloodstream via microscopic tubes known as nephrons. The nephrons separate the blood from waste substances, toxins, and chemicals, reabsorb the water and important nutrients back in the blood via diffusion.
4. Liver
The liver synthesizes proteins in the human body and in the process of that synthesis it also produces a potentially harmful waste product known as urea. Thankfully, with the help of diffusion, the urea diffuses into our bloodstream just upstream of our kidneys and is then filtered out.
Examples of Diffusion in Nature
Diffusion is truly a universal physical phenomenon, and so many natural processes depend on it.
1. Air Pollution
Air possesses approximately 21% oxygen, 1% argon, 78% nitrogen, and 0.04% carbon dioxide along with trace amounts of other gasses in its natural state. Many mechanical, agricultural, and industrial processes produce waste stuff as a by-product that diffuses into the air and pollutes it.
2. Crystals
Crystals naturally have vacant spaces in their atomic structure through which the atoms can diffuse. When you compress a crystal, the atoms go into those tiny vacancies, as a result, they create new vacancies and this changes the atomic structure of the crystal.
3. Intracellular Motion
Intracellular motion is the motion that happens inside one side instead of between multiple cells. Diffusion occurs when a new chemical or substance enters the cytosol of a cell. The cytosol is fluid and is a part of a cell’s insides. When a new particle, chemical, or molecule enters the cell, it diffuses uniformly through the cytosol.
4. Leaves
Leaves also make use of diffusion during the night. Plants breathe in Carbon Dioxide (CO2) during the day and, as a result, breathe out oxygen via osmosis (it opens and closes the stomata). However, during nighttime, the stomata remain open so osmosis is not required and Carbon Dioxide (CO2) enters the plant via diffusion.
Factors that Influence Diffusion
Many factors can influence the process of diffusion and disrupt it even. Some of those factors include particle size, temperature, steepness of the concentration gradient, and area of interaction. These factors, on their own, and collectively can change the extent, intensity, and rate of diffusion.
1. Temperature
In every system, the molecules move with a specific amount of kinetic energy which is normally not directed in any certain manner and if you look at it, it might appear totally random. When these moving molecules collide with each other, the direction in which they are moving changes. With the change in their direction, their velocity and momentum also change.
Let’s take the example of a block of dry ice. Dry ice is basically just Carbon Dioxide in solid form, and let’s place this block of dry ice inside a container. The molecules of carbon dioxide present in the center of the block will majorly just mostly collide with one another and they will remain inside the solid mass. However, the molecules that are located in the periphery, the rapidly moving molecules present in the air will affect their movement as well, and, as a result, the peripheral molecules will begin to diffuse into the air. This process results in the formation of a concentration gradient, in which the concentration of carbon dioxide is slowly reduced with distance from the block of dry ice.
What happens in such scenarios is that the kinetic energy of all molecules present in a system increases as the temperature increases. As a result, the rate at which solute and solvent molecules move increases and their collisions also increase. In other words, the block of dry ice (or even regular ice) will undergo evaporation quicker when it is warm outside because the molecule will move with more energy and will quickly escape the solid-state.
2. Area of Interaction
Let’s continue with the example discussed above of the block of dry ice. Imagine if you break that block of dry ice into a lot of pieces, the area of that ice that interacts with the atmosphere surrounding it also increases immediately. Consequently, the number of molecules of Carbon Dioxide that only collide with other molecules of the gas within dry ice decreases, and the rate with which they diffuse into the air increases.
You can understand the area of interaction and its influence on the process of diffusion even better if the gas you are experimenting with has color.
For example, if you sublimate iodine over a hot stove or bunsen burner, you will notice that purple fumes are formed when you heat it and mix it with the air. If you carry out the sublimation in a narrow crucible, you will notice that the fumes will gradually diffuse towards the mouth of that narrow crucible and will disappear rapidly. The reason behind this is that when the surface area is smaller, the rate of diffusion of a substance remains low.
You can also observe this when you mix two liquid reactants. You will notice that as you stir them the area of interaction of the chemicals will increase and it will allow them to diffuse more quickly.
3. Steepness of The Concentration Gradient
The process of diffusion is mainly powered by the probability of molecules. For instance, when you diffuse iodine gas, if you place the narrow crucible in another closed container and heat the iodine crystals for a long time, the rate at which the purple gas disappears (as discussed above) will decrease. This reduction in its disappearance is because, as time goes on, the larger container, in which the narrow crucible is enclosed, starts to have enough iodine gas that some of that gas will start going back to the narrow crucible.
4. Particle Size
No matter what the temperature, the rate at which a smaller particle diffuses will always be more rapid than the rate at which a larger-sized molecule diffuses. This is influenced by both the surface areas and the mass of the molecule because a heavier molecule with a larger mass and larger surface area will diffuse slowly. On the other hand, a lighter molecule with a smaller mass and smaller surface area will diffuse more quickly.
For instance, if we look at oxygen gas; its molecules will undergo diffusion more quickly as compared to the molecules of carbon dioxide. However, if we compare both of them to iodine gas, then both Carbon Dioxide and Oxygen will diffuse more quickly.
What is Identity Diffusion?
The concept of identity diffusion is not directly related to the diffusion we are discussing, however, many people still mistake it for a type of diffusion because of its name.
Identity diffusion is a phenomenon in which people who have this said condition have not committed to a specific path to attain their future and are not even making any effort to come up with a plan. This included both occupational and ideological futures.
Normally, people undergo identity diffusion during their adolescence because it is a time when people are still working on their identities, but it can pass on to adulthood.
What is Passive Diffusion?
Passive diffusion can be defined as the by which molecules diffuse from a place with a higher concentration to a place with a lower concentration and it is vital for the passage of important drugs through membranes. For instance, if we talk about lipid-soluble drugs, they can penetrate lipid membranes without any difficulty.
Conclusion
And there you have a complete rundown of diffusion, its types, its examples, and the factors that can influence the rate of diffusion. If you want to understand the concept of diffusion better, we recommend you ask your physics tutor to explain its types and examples with real-life examples.
We hope we were able to clear your concept of diffusion. Best of luck!
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