Viscosity The viscosity of a fluid is a measure up of the difficulty which molecules have actually passing each other in a fluid. The is dependent ~ above the size and shape the the molecules and by the magnitude of the cohesive forces and also intermolecular bonds such as hydrogen bonding. Spherical molecules have actually less circulation resistance than long molecules which can come to be entangled. Very viscous liquids have tendency to be long chained molecules. Because that example, honey has a much greater viscosity 보다 water. Viscosity is very dependent ~ above temperature, diminish with raised temperature.
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Why is honey more viscous than water? honey is a mixture of mostly of fructose, glucose and also water and also with the continuing to be ingredients composed of miscellaneous saccharine, essential acids, minerals and also enzymes. Love husband in part is an ext viscous (thick) than water due to strong inter-molecular forces. However in enhancement the structure of glucose, fructose and other saccharine are big in size contrasted to water molecules and also can come to be entangled. Viscosity defines how a fluid resists forces, or an ext specifically shear forces. Shear is the kind of pressure that occurs as soon as two objects slide parallel to one another. Fluids through low viscosity have actually a short resistance come shear forces, and also therefore the molecules flow quickly and are straightforward to move through. A fluid that has no resistance to shear tension is known as one ideal fluid or inviscid fluid. Zero viscosity is observed just at really low temperatures. Otherwise, every fluids have positive viscosity, and also are technically said to be viscous or viscid. However, a fluid is claimed to be viscous if that viscosity is substantially greater than water"s, and also may be defined as mobile if the viscosity is noticeably less than water"s. If the viscosity is very high, the liquid will appear to be a hard in the quick term. The SI physical unit of dynamic viscosity is the pascal-second (Pa·s), (equivalent to (N·s)/m2, or kg/(m·s)). The devices for viscosity space the centipoise or poise but can it is in expressed in other acceptable dimensions as well. Some conversion factors are as follows:

100 Centipoise = 1 Poise 1 Centipoise = 1 mPa s (Millipascal Second) 1 Poise = 0.1 Pa s (Pascal Second) Centipoise = Centistoke x particular Gravity

How is Viscosity Measured?

The formula for measuring viscosity:

viscosity = shear stress/ shear rate

A shear anxiety is identified as the component of stress coplanar through a product cross section. Shear stress arises from the pressure vector ingredient parallel come the cross section. Shear stress = force applied/cross-sectional area of product with area parallel come the applied force vector

The shear rate for a liquid flowing between two parallel plates, one relocating at a consistent speed and the various other one stationary (Couette flow), is characterized by:

shear price = velocity the the relocating plate, measure in meters every second/ the distance in between the 2 parallel plates, measure up in meters.

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The units are expressed in centipoise(cP), i m sorry is the tantamount of 1 mPa s (millipascal second).

Approximate Viscosities of usual Materials (At Room Temperature-70°F) *

Material Viscosity in Centipoise
Water 1 cps
Milk 3 cps
SAE 40 motor Oil 650-900 cps
Castrol Oil 1,000 cps
Honey 10,000 cps
Ketchup 50,000 cps
Sour Cream 100,000 cps
Peanut Butter 250,000 cps

Newtonian vs. Non-Newtonian Fluids

Isaac Newton, the guy who found the over formula, thought that, in ~ a offered temperature and also shear stress, the viscosity the a liquid would remain constant regardless of transforms to the shear rate.

He was only partly right. A few fluids, such together water and also honey, carry out behave this way. We call these fluidsNewtonian fluids. Many fluids, however, have viscosities the fluctuate depending on the shear rate. These room calledNon-Newtonian fluids.

A non-Newtonian liquid is a fluid whose flow properties different in any means from those that Newtonian fluids. Most commonly, the viscosity (the measure up of a fluid"s ability to resist steady deformation by shear or tensile stresses) that non-Newtonian fluids is dependent on shear price or shear price history.

There are five types of non-Newtonian fluids: thixotropic, rheopectic, pseudoplastic, dilatant, and also plastic. Different considerations are required when measuring each of these liquid types. See species of Non-Newtonian fluids for much more details.

Many generally found substances room non-Newtonian fluids, such as ketchup, custard, toothpaste, starch suspensions, paint, blood, and also shampoo.

Example of: slim thickening where viscosity increases with boosted stress: cornstarch and water.: sand and water

Examples of thin thinning whereby viscosity decreases with enhanced stress: whipped cream, ketchup, latex paint


Viscosity in the Food Industry

Viscosity measurements are used in the food market to maximize production efficiency and also cost effectiveness. The affects the rate at which a product travels v a pipe, how long the takes to collection or dry, and the time it takes to dispense the fluid into packaging. The production procedure has to it is in designed v the viscosity the the product in mind, making certain that pipes space angled come optimize flow, or that dispensers provide the appropriate amount of pressure to induce flow, yet not so much that the packaging will overfill.

Viscosity is also a characteristic of the texture of food.The product’s viscosity must be measured and also monitored during production to ensure that each batch is consistent and also will go with the production process efficiently.

Non-Newtonian Fluids in Food Design

Many frequently found substances space non-Newtonian fluids, such as ketchup, custard, mustard, whip cream and also various food thickening agents.

See more: What Is The Lewis Structure Of N2 (Nitrogen Gas)? Chemical Bonding: N 2 Lewis Structure

Non-Newtonian shear thinning is one obviously desirable attribute that enables a condiment come be yielded easily from a bottle (low viscosity in ~ "squeezing" shear rates) and yet retain a well-off texture top top the plate (high viscosity at short shear rates). Comparison this behavior to the Newtonian flow of love husband which necessitates a tough squeeze on distribution yet operation under its own weight.

References and Readings

Hands-on Activity: measuring Viscosity Why doesn"t the viscosity that water readjust much through temperature favor it go for various other substances? no Newtonian Fluids science of Food Thickening Agents Rheology experimentation reveals a human being of difference in between condiments of similar viscosity values


Test your Understanding: 1. What statement is no true about viscosity a) Viscosity defines how a fluid resists forces b) Viscosity continues to be constain regardless of shear stress c) viscosity is a measure of the challenge which molecules have actually passing each various other in a fluid d) Viscosity is dependent ~ above the size and also shape of molecule 2. Why is honey much more viscous than water? a) because honey contains large molecules and also can come to be entangled b) due to the fact that many the the molecules space bonded come each various other c) early to solid inter-molecular forces d) both a and also c room correct 3. Why is the knowledge of viscosity import for the food industry. a) Many generally found substances space non-Newtonian fluids, such together ketchup, custard, mustard, whip cream and various food thickening agents. b) Non-Newtonian shear thinning enables fluids to conveniently be eliminated from containers however retain form on the key c) viscosity is crucial in developing food thickeners d) all of the over 4. What are the units for viscosity in the SI System: a) newton m/sec2 b) the newton-second every square meter or a Pascal second (Pa*s) c) Centipoise or MilliPascal second d) joules m/sec2 5. Under what problems can us observe zero viscosity a) at really high temperatures b) at zero degrees Centigrade c) in the real people viscosity have the right to only be it was observed at really low temperatures