What is Viscosity in The Field of Chemistry
Example of Viscosity
- Cooking Oil
- Honey
- Lubricant
- Engine Oil
- Brake Oil
- Liquid Soap
Definition of Viscosity
What is Viscosity
Understand viscosity very simply?
Now we are going to explain viscosity so simply that a kid can also understand.
Imagine you have two bottles: one filled with water and the other with honey. When you pour them out, you'll notice that water flows quickly and easily, while honey flows slowly and is much thicker.
Viscosity is a way to describe how thick or thin a liquid is and how easily it flows. Water has low viscosity because it flows easily, while honey has high viscosity because it flows slowly and is sticky.
So, in simple terms, viscosity is like the "thickness" of a liquid and how fast or slow it moves.
Let's use some everyday examples to explain viscosity:
- Water vs. Honey: Imagine you have a glass of water and a jar of honey. When you pour water, it flows quickly and easily. But when you pour honey, it flows slowly and is thick. Water has low viscosity, and honey has high viscosity.
- Ketchup: When you try to pour ketchup from a bottle, it doesn't come out easily because it's thick. You might have to shake the bottle or squeeze it. Ketchup has high viscosity.
- Oil vs. Syrup: If you pour cooking oil and maple syrup, you'll notice that oil flows faster and more smoothly than syrup. Oil has lower viscosity compared to syrup.
So, viscosity is like the "thickness" of a liquid and how easily it flows. Low viscosity means it flows easily (like water), and high viscosity means it flows slowly (like honey or ketchup).
What is absolute viscosity?
Absolute viscosity is also known as dynamic viscosity. It is a fundamental property of a fluid that describes its resistance to shear or flow when subjected to an applied force.
It quantifies how easily a fluid deforms or flows when a shearing force is applied to it. The SI unit of absolute viscosity is the pascal-second (Pas), but other units like the poise (P) and the centipoise (cP) are also commonly used.
What is Meaning of Viscous
Who Poses Viscosity
Formula of Viscosity
Newton’s Viscosity Law
Unit of Viscosity
Relation of viscosity with temperature
Temperature -> | 27 °C | 77 °C |
Viscosity of Water | 0.85×10-3 pascal second | 0.36×10-3 pascal second |
Viscosity of Air | 1.85×10-5 pascal second | 2.08×10-5 pascal second |
Types of Viscosity
1. Dynamic Viscosity
Formula of Dynamic Viscosity
Formula of Kinematic Viscosity
Viscometers and its uses
Viscometers are scientific instruments designed to measure the viscosity of a fluid. Viscosity is a measure of a fluid's resistance to flow. Viscosity is a critical property in various fields of science, chemistry and industry.
Viscometers are essential tools for determining the flow behaviour and consistency of liquids, and they have a wide range of uses across different applications.
Some of the primary uses of viscometers:
1. Quality Control in Manufacturing: Viscometers are commonly used in industries such as food and beverages, pharmaceuticals, cosmetics, oils and chemicals to ensure product quality and consistency. Manufacturers can use viscometers to check the viscosity of raw materials and finished products to meet specific quality standards.
I personally used viscometers in QC lab to test viscosity of engine oils in Savita Oil Technology Ltd.
2. Oil and Petroleum Industry: In the oil and petroleum industry, viscometers are crucial for measuring the viscosity of crude oil, lubricants, and fuel oils. This information is essential for product formulation, transportation, and ensuring proper lubrication in machinery and engines.
3. Paints and Coatings: Viscosity plays a significant role in the application and performance of paints and coatings. Viscometers help manufacturers control the viscosity of paint formulations to ensure they are suitable for spraying, brushing, or rolling onto surfaces.
4. Pharmaceuticals: Pharmaceutical companies use viscometers to measure the viscosity of drug formulations, including syrups, suspensions, and creams. Consistency in viscosity is crucial to ensure accurate dosing and drug delivery. Viscosity results plays important roles in stablishing the quality standards of many drugs.
Now I am working in pharma company, and we will always check that viscosity results are within range in drug analysis COA (Certificate of analysis) along with other quality parameters.
5. Food and Beverage Industry: In the food industry, viscometers are used to measure the viscosity of various products, including sauces, beverages, and dairy products. Proper viscosity ensures the desired texture and mouthfeel of food products.
6. Polymer and Plastics: The viscosity of polymer melts is vital in the manufacturing of plastics, rubber, and other polymer-based products. Viscometers help control the processing conditions and quality of these materials.
7. Environmental Testing: Viscometers are used in environmental studies and water quality analysis to measure the viscosity of water samples and other liquids. Changes in viscosity can provide insights into the presence of pollutants or contaminants.
8. Research and Development: Scientists and researchers use viscometers to investigate the rheological properties of fluids, conduct experiments, and develop new materials. Viscometry is essential in various scientific disciplines, including chemistry, physics, and materials science.
9. Cosmetics and Personal Care: In the cosmetics industry, viscometers are used to assess the consistency and texture of skincare products, shampoos, and lotions. This ensures that the products are easy to apply and provide the desired sensory experience.
10. Biotechnology and Pharmaceuticals: Viscometers are used in biotechnology and pharmaceutical research to measure the viscosity of biological fluids, such as blood or cell culture media. Understanding viscosity can aid in the development of drug delivery systems and medical devices.
Overall, viscometers are versatile instruments that play a crucial role in ensuring product quality, optimizing manufacturing processes, and advancing scientific research in a wide range of industries. They come in various types, including rotational viscometers, capillary viscometers, and vibrational viscometers, each suited to specific analysis, research, testing application and measurement requirements.
Newtonian and nonnewtonian fluids
Example of Newtonian and nonnewtonian fluids
Newtonian Fluids
Newtonian fluids have a constant viscosity regardless of the applied stress. Their flow behaviour is linear and predictable. Examples include:
- Water: Flows easily and has a constant viscosity.
- Air: A gas that behaves predictably under different conditions.
- Alcohol: Maintains a consistent flow and viscosity.
Non-Newtonian Fluids
Non-Newtonian fluids have a viscosity that changes with the applied stress or shear rate. Their flow behaviour is non-linear and can be quite interesting. Examples include:
- Ketchup: Becomes less viscous when shaken or squeezed (shear-thinning behaviour).
- Cornstarch and Water Mixture (Oobleck): Acts like a solid when a sudden force is applied but flows like a liquid under slow movement (shear-thickening behaviour).
- Toothpaste: Flows easily when squeezed out of the tube but stays in place on the toothbrush (yield stress behaviour).
Characteristics of Newtonian Fluids:
Characteristics of Non-Newtonian Fluids:
What is the viscosity of water:
The viscosity of water (H2O) at the room temperature (that is at about 20 degrees Celsius or 68 degrees Fahrenheit) is approximately 1.002 millipascal-seconds (mPa·s) or 1.002 centipoise (cP).
This measurement value of 1.002 mPa·s (approx.) represents the resistance of water to flow and is used as a reference point for measuring the viscosity of other liquids. Viscosity can change with temperature; generally, water becomes less viscous as it is heated and more viscous as it cools.
Water is a chemical compound with chemical formula H2O. Water molecule contains two hydrogen and one oxygen atom. These atoms are connected by covalent bonds to form water molecule. This water molecule is essential for life on earth. Water molecules act as universal solvent for both living and non-living things. So, this chemical compound (water) is very essential for life on this planet earth.
Dynamic viscosity & kinematic viscosity of water
Dynamic viscosity & kinematic viscosity of water along with density at different temperatures from 20°C to 30°C.
Temp. [°C] | Dyn. Viscosity [mPa.s] | Kin. Viscosity [mm²/s] | Density [g/cm³] |
20 | 1.002 | 1.003 | 0.998 |
21 | 0.978 | 0.980 | 0.998 |
22 | 0.954 | 0.957 | 0.998 |
23 | 0.932 | 0.934 | 0.998 |
24 | 0.911 | 0.913 | 0.997 |
25 | 0.890 | 0.893 | 0.997 |
26 | 0.870 | 0.873 | 0.997 |
27 | 0.851 | 0.854 | 0.997 |
28 | 0.832 | 0.836 | 0.996 |
29 | 0.815 | 0.818 | 0.996 |
30 | 0.797 | 0.801 | 0.996 |
Uses of Viscosity in Real world
- Viscosity plays a crucial role in many real-world applications. Here are some of the examples of real world uses or applications of viscosity:Automgtive Industry: Engine oils are designed with specific viscosities to ensure proper lubrication of engine parts. The right viscosity helps reduce friction and wear, improving engine performance and longevity.
- Food Industry: The viscosity of sauces, syrups, and other food products affects their texture and how they pour. For example, ketchup is designed to have a specific viscosity so it flows smoothly but not too quickly.
- Medicine: The viscosity of blood is an important factor in diagnosing and treating various medical conditions. Blood thinners, for example, are used to reduce blood viscosity and prevent clots.
- Cosmetics: The viscosity of lotions, creams, and shampoos affects their application and feel on the skin or hair. Manufacturers adjust viscosity to create products that are easy to use and effective.
- Paints and Coatings: The viscosity of paints and coatings determines how they spread and adhere to surfaces. Proper viscosity ensures a smooth, even application without drips or runs.
- Lubricants: Industrial machinery relies on lubricants with specific viscosities to reduce friction and wear between moving parts. The right viscosity ensures efficient operation and extends the life of the equipment.
- Inkjet Printing: The viscosity of ink affects how it flows through the printer nozzles and onto the paper. Proper viscosity ensures sharp, clear prints without smudging.
- Pharmaceuticals: The viscosity of liquid medications affects their dosing and administration. For example, syrups need to have the right viscosity to be easily swallowed and accurately measured.
- Chemical Engineering: Viscosity is a key factor in the design and operation of chemical reactors and pipelines. It affects the flow rates and mixing of reactants, impacting the efficiency of chemical processes.
- Environmental Science: The viscosity of pollutants, such as oil spills, affects their spread and cleanup. Understanding viscosity helps in developing effective methods for environmental remediation.
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Very Nice Explanation.
ReplyDeletehydrometer (show relative density(specific gravity) on hydrometer graduated scale).
Density of substance = reading at hydrometer x density of water at that temp. of substance
weighing balance
thermometer
ostwald viscometer
graduated cylinder
Relative density = hydrometer
Specific gravity is the density of a substance divided by the density of water.
Since (at standard temperature and pressure) water has a density of 1 gram/cm3,
and since all of the units cancel, specific gravity is usually very close to the same value as density (but without any units).
Specific gravity = Density of substance/density of water = weight of substance/weight of water
How tightly packed = how much / how big
or
Density = Mass / Volume
Instruments used to measure viscosity
Capillary Viscometer (The earliest methods for measuring viscosity were based on using capillary tubes and measuring the time it took for a volume of liquid to pass through the length of the tube.- Ostwald or Ubbelohde viscometers)
Zahn Cup (which is a small container with a handle, and a small hole in the bottom. The time it takes to empty the cup through the hole is correlated to viscosity. The Zahn cup is often used in the paint industry.)
Falling Sphere Viscometer (Falling Sphere Viscometer)
Vibrational Viscometer (Vibrational Viscometers measure the damping of an oscillating electromechanical resonator immersed in a fluid. This technique is often used in-process to give continuous readings in a product stream, batch vessel, or in other process applications.)
Rotational Viscometer (The rotational viscometer measures the torque required to turn an object in a fluid as a function of that fluid’s viscosity. This method is frequently used in quality control, and in production laboratories.)
Determination of viscosity of liquid using ostwald viscometer
V1 =((D1T1)/(D2T2))xV2
V1 = Viscosity of unknown liquid (Whoes to be calculated)
D1 = Density of unknown liquid
t1 = Time of flow of unknown liquid
V2 = Viscosity of standard liquid
D2 = Density of standard liquid
t2 = Time of flow of standard liquid
Requirement:-
Chemicals-
Distilled water
Ethanol
Acetone
Apparatus-
Ostwald viscometer
Electronic balance
Stopwatch