Introduction
In chemistry related to fluids, it becomes imperative to study the internal motion or the process being executed when a force or a change in the state of motion of the fluid is being exerted on it. Regarding the study of fluids, an important property was discovered which was termed Viscosity. Viscosity was first proposed by Sir Isaac Newton who also gave the well-known law of viscosity. Before getting into the topic of high viscosity vs low viscosity, let us first know about an important term which is the Adjacent layer of fluids.
Adjacent layers of fluid are layers of the fluid that are near each other, with each layer moving at a different velocity. The layers are separated by a small distance known as the boundary layer.
The concept of adjacent layers of fluid was first proposed by Sir Isaac Newton in his book “Philosophi忙 Naturalis Principia Mathematica” (Mathematical Principles of Natural Philosophy) in 1687. In this book, Newton proposed that when a force is applied to a fluid, such as when a liquid flows through a pipe or a gas moves past an object, the fluid forms adjacent layers that slide past each other with different velocities.
Definition
The term Viscosity can be defined as follows: Viscosity is a property of a fluid that describes the resistance in motion between the internal layers of a fluid.
As we have studied earlier that fluid can internally be divided into multiple layers which possess different velocities. These velocities may have different directions as well. So, due to the difference in velocities of the layers, there exists an opposing force that resists the flow of fluid.
Due to this, the fluid may be highly viscous or low viscous. The terms high viscosity and low viscosity will be discussed further.
Viscosity is generally measured by the unit known as Pascal-second or centipoise. Viscosity plays an important role in many industrial and scientific applications, including fluid dynamics, chemical engineering, and lubrication. Understanding and controlling viscosity is crucial in industries such as oil and gas, food processing, and pharmaceuticals.
Viscosity also depends upon certain factors such as size, shape, and interaction between molecules of the fluid.
What is High Viscosity?
High viscosity refers to the viscosity of the fluid which has a high amount of resistance to the flow, amongst its internal layers. Fluids with high viscosity are known as high-viscous fluids.
These fluids when subjected to flow have very slow motion as they are highly resistant to flow and also oppose deformations. Fluids can have high viscosity due to various reasons, which include temperature, pressure, molecular interaction, and size of molecules.
When the molecules of the fluid have strong forces of interaction between them, then the fluid has high viscosity. Bonds such as dipole-dipole interaction and hydrogen bonding can be responsible for the phenomenon.
When there is a low temperature in the surroundings it results in high viscosity as the molecules do not get enough energy to easily slide over others. Similarly, high pressure is also suitable for fluid to attain high viscosity.
What is Low Viscosity?
A fluid is said to have low viscosity if the layers of the fluid easily slide over each other, that is the friction between them is comparatively low and it does not resist the flow of motion of the fluid.
Low viscous fluids can also be deformed easily, since they have a good flow in the motion it does not oppose the fluid to be deformed.
Higher temperatures and low pressure is the most suitable condition for a fluid to have low viscosity. At higher temperatures, molecules of the fluid gains energy and become excited due to it. This causes the flow of layers to be smooth in nature.
The fluids with low viscosity have very weak interactions between their molecules. Due to this, the molecules of the adjacent layers generate very less friction in the movement or motion of the fluid. Forces like London force or Weak Van Der Waal鈥檚 forces can possibly be present in low viscous fluids.
Difference between High viscosity and Low viscosity
High Viscosity |
Low Viscosity |
| High resistance to shear and tensile forces | Does not resist any forces. |
| Does not deform easily. | Low viscous fluids can easily be deformed. |
| High viscous fluids are thick and sticky. | Low viscous fluids are thin and runny. |
| Resistance to flow is very high. | These fluids can easily flow. |
| Surface tension is very high in these fluids. | Low viscous fluids have low surface tension. |
| Molecules have strong interactions between them. | Poor molecular interaction is present. |
| Low temperature and high-pressure increase viscosity. | High temperature and low-pressure decrease viscosity. |
| High viscous are used in places where resistance to flow and deformation is useful. | Used in places that require a good flow of fluid. |
| Example – Honey, tar, etc. | Examples – water, alcohol, etc. |
Examples of Viscosity of some common fluids
In the present world there are multiple fluids that we use in our day-to-day life and which become necessary for the operation of a smooth living, one such fluid is water. While some fluids are used for cooking purposes, some are used in heavy machinery. Depending on the viscosity they possess each fluid is useful in a particular industry or process. Hence, knowing about the viscosity of some important fluids is a necessity.
Some highly viscous nature fluids:
1. Honey: 2-10 Pa路s or 2,000-10,000 cP
2. Motor oil: 10-20 Pa路s or 10,000-20,000 cP
3. Ketchup: 50-100 Pa路s or 50,000-100,000 cP
4. Corn syrup: 1,000-2,000 Pa路s or 1,000,000-2,000,000 cP
5. Printer’s ink: 10-100 Pa路s or 10,000-100,000 cP
6. Chocolate syrup: 50-100 Pa路s or 50,000-100,000 cP
Low-viscosity fluids are:
1. Blood: 3-4 mPa路s or 3-4 cP
2. Ethanol (alcohol): 0.0012 Pa路s or 1.2 cP
3. Olive oil: 0.07-0.12 Pa路s or 70-120 cP
4. Water: 0.001 Pa路s or 1 cP
5. Milk: 3-5 mPa路s or 3-5 cP
6. Gasoline: 0.0005-0.0015 Pa路s or 0.5-1.5 cP
Importance Of Viscosity
Viscosity holds great significance as well as importance in the industrial sector, research sector as well as in common day-to-day life in several ways. Here are some of the importance of viscosity:
1. Material characterization
It is important in the characterization and differentiation of materials based on their flow behavior. This is useful in materials science, where different materials may have different viscosities depending on their composition and molecular structure.
2. Quality control
In manufacturing processes and industrial production work viscosity can provide the measurement in order to ensure the quality of a particular product or a material being used for production. For example, if a product’s viscosity is not within a certain range, it may indicate a problem with the manufacturing process or an issue with the product itself.
3. Fluid dynamics
In the field of fluid dynamics, in order to know about the flow of any fluid material through various arrangements the analysis of its viscosity plays a crucial role, as knowing the viscosity of any fluid can predict its flow. This knowledge is useful in a wide range of fields, including engineering, geology, and environmental science.
4. Process optimization
Viscosity measurements can be used to optimize various processes, such as in the mixing of fluids, the injection of materials, and the flow of fluids through porous media. This can lead to more efficient and effective processes that save time and resources.
5. Safety
In some applications, such as in the handling of highly viscous materials like molten metals or hot asphalt, understanding the viscosity of the material is important for ensuring worker safety and preventing accidents.
Overall, the importance of viscosity lies in its ability to provide insights into the behavior of fluids and materials, and its practical applications in a wide range of fields and industries.
Applications
After knowing about the importance of viscosity let us now discuss some of its real-life applications.
1. Lubrication
Fluids of various viscosity are used as lubricants in the machinery in order to maintain the smooth operation and function of moving parts in machines used for industrial purposes or even in household work. In heavy machinery which generates a large amount of heat, we use highly viscous fluids as these are resistant to deformation and hence provide a smooth medium for the parts to move.
2. Flow control
Viscosity is used to control the flow of fluids in various processes, such as chemical manufacturing, food processing, and inkjet printing.
3. Coating and adhesion
Coating is the process that is done, in order to provide a protective layer to the equipment or any object. High viscous fluids such as heavy-duty paints are often used to provide the objects with a thick protective layer. Materials that are used as adhesives also have high Viscosity.
4. Injection molding
Injection molding is a process in which molten plastic is injected into the mold and is allowed to cool in order to cast the required shape, viscosity plays a crucial role in the completion of this process as determining the viscosity of the molten plastic can find out that if the plastic material would be injected smoothly or not.
5. Medical applications
Viscosity can be useful in medical fields as some diseases can be identified with the help of this analysis. If the viscosity of a sample of blood is not in the normal range then a person is possibly suffering from a disease. Quality checks of various medications can also be done using the viscosity analysis. It is also important in the design of medical devices, such as syringes and catheters.
6. Cooling and heat transfer
Low-viscosity fluids such as water and ethylene glycol are commonly used as coolants in various applications such as air conditioning, refrigeration, and engine cooling. These fluids are also used as heat transfer fluids in heating and cooling systems.
7. Hydraulic systems
Fluids that are low-viscosity like hydraulic oils are used in hydraulic systems to transmit power, control motion, and lubricate moving parts.
8. Pharmaceuticals
Low-viscosity fluids such as saline solutions are used in the production of pharmaceuticals for various purposes such as dilution, injection, and solvents.
9. Cleaning solutions
Low-viscosity cleaning solutions such as detergents and soaps are used for cleaning surfaces, fabrics, and dishes.
10. Cosmetics
Lotions, creams, and gels (low-viscosity fluids) are used in various cosmetic products for moisturizing, smoothing, and other skincare benefits.
Q&A
1. Is Higher viscosity thicker or thinner?
High viscous fluids are thicker in nature due to their molecular interactions and resistance to the flow of fluid
2. Which is better high or low viscosity?
In general both the kind of viscosities are favorable like in the lubrication of heavy machines high viscous fluids are preferred while in places that require coolants low viscous fluids are preferred.
3. What does it mean if the viscosity is high?
High viscosity in a fluid indicates that the molecular bonding in the fluid is very strong and the fluid is thicker in nature.
4. What does it mean if the viscosity is low?
Low viscosity in a fluid indicates that the molecular bonding in the fluid is very weak and the fluid is thinner in nature.
Let us know to summarize this topic and recall what we have studied in this article.
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Written By: Bharat Awasthi
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