Note the correlation between the surface tension of a liquid and the strength of the intermolecular forces: the stronger the intermolecular forces. more the intermolecular forces, lesser is the vapour pressure this is how it goes Vapor pressure is the amount of gas in equilibrium with the liquid and solid phases. The higher the In the end, we can make the overall relationship that. Answer to What is viscosity? What is the relationship between the intermolecular forces that exist in a liquid and its viscosity?.
They are low-viscosity fluids. High-viscosity fluids resist deformation. Consequently, they do not flow easily. Comparing high-viscosity fluid to low-viscosity fluid. At the same temperature, the former flows slower than the latter.
From ideally viscous liquids to elastic solids.
Relation between intermolecular bonding and the viscosity of a liquid?
Viscoelastic materials in everyday life. The two plates model Figure 3: The virtual viscous sandwich: Laminar flow consisting of infinitesimally thin layers. The two-plates model provides a mathematical description for viscosity. Think of a kind of sandwich : There are two plates with fluid placed in-between. The correct calculation of parameters related to viscosity depends on two criteria: The fluid does not glide along the plates but is in good contact with them.
Scientifically speaking, an adhesive force operates between fluid and plates. The flow is laminar. It forms infinitesimally thin layers and no turbulence i. You can picture laminar flow as a stack of paper sheets or beer mats. The lower plate does not move. The upper plate drifts aside very slowly and subjects the fluid to a stress, which is parallel to its surface: Shear stress Figure 4: Using the two-plates model to calculate the shear stress.
Using the two-plates model to calculate the shear rate.
Shear rate is the velocity of the moving plate divided by the distance between the plates. The two-plates model allows for calculating another parameter: The shear rate is the velocity of the upper plate in meters per second divided by the distance between the two plates in meters.
Therefore, the viscosity eta is shear stress divided by shear rate. Only Newtonian liquids can be described by this simple relation. Dynamic viscosity is shear stress divided by shear rate. What are Newtonian liquids? Viscosity functions show dynamic viscosity vs. Different types of flow behavior: A viscosity function shows the viscosity over the shear rate. For a Newtonian liquid, this function is a straight line curve 1 ; see figure 6.
Basics of viscometry :: Anton Paar Wiki
Typical Newtonian liquids are water or salad oil. If its viscosity changes with the shear rate, a liquid is non-Newtonian and — for exact definition — one has to specify the apparent viscosity. Different shear-dependent fluids behave differently: For some, their viscosity decreases when the shear rate increases curve 2 e. The flow behavior of non-Newtonian liquids can be far more complex than these basic examples. Still, shear rate is not the only influencer.
What influences flow behavior? A highly viscous substance features tightly linked molecules. The shear rate or the shear stress, respectively, as external force.
This includes all kinds of actions: The influence further depends on the strength and on the duration of the external force. These parameters determine under which conditions a substance flows and which type of flow it develops. To measure viscosity, laminar flow is required. Inner molecular structure, outside forces acting on the material, and current ambient conditions Figure 8. In laminar flow, molecules move in orderly layers, while in turbulent flow they follow no pattern.
Laminar or turbulent flow Laminar flow means that the substance moves in imaginary thin layers. Molecules do not move from one layer to another, their movement forms a regular pattern.
The moisture is absorbed by the entire fabric, not just the layer in contact with your body. Some liquids, such as gasoline, ethanol, and water, flow very readily and hence have a low viscosity. Others, such as motor oil, molasses, and maple syrup, flow very slowly and have a high viscosity.
The two most common methods for evaluating the viscosity of a liquid are 1 to measure the time it takes for a quantity of liquid to flow through a narrow vertical tube and 2 to measure the time it takes steel balls to fall through a given volume of the liquid.
The higher the viscosity, the slower the liquid flows through the tube and the steel balls fall. The viscosities of some representative liquids are listed in Table Because a liquid can flow only if the molecules can move past one another with minimal resistance, strong intermolecular attractive forces make it more difficult for molecules to move with respect to one another. This effect is due to the increased number of hydrogen bonds that can form between hydroxyl groups in adjacent molecules, resulting in dramatically stronger intermolecular attractive forces.
There is also a correlation between viscosity and molecular shape. Liquids consisting of long, flexible molecules tend to have higher viscosities than those composed of more spherical or shorter-chain molecules. London dispersion forces also increase with chain length.
- 11.4: Intermolecular Forces in Action: Surface Tension, Viscosity, and Capillary Action
Due to a combination of these two effects, long-chain hydrocarbons such as motor oils are highly viscous. Viscosity increases as intermolecular interactions or molecular size increases. Motor Oils Motor oils and other lubricants demonstrate the practical importance of controlling viscosity.
Viscosity decreases rapidly with increasing temperatures because the kinetic energy of the molecules increases, and higher kinetic energy enables the molecules to overcome the attractive forces that prevent the liquid from flowing.
So-called single-grade oils can cause major problems. If they are viscous enough to work at high operating temperatures SAE 50, for examplethen at low temperatures, they can be so viscous that a car is difficult to start or an engine is not properly lubricated.
These properties are achieved by a careful blend of additives that modulate the intermolecular interactions in the oil, thereby controlling the temperature dependence of the viscosity. Will the oil be pulled up into the tube by capillary action or pushed down below the surface of the liquid in the beaker? What will be the shape of the meniscus convex or concave? Identify the cohesive forces in the motor oil.
Determine whether the forces interact with the surface of glass. From the strength of this interaction, predict the behavior of the oil and the shape of the meniscus. Solution A Motor oil is a nonpolar liquid consisting largely of hydrocarbon chains.
The cohesive forces responsible for its high boiling point are almost solely London dispersion forces between the hydrocarbon chains. B Such a liquid cannot form strong interactions with the polar Si—OH groups of glass, so the surface of the oil inside the capillary will be lower than the level of the liquid in the beaker.
Relation between intermolecular bonding and the viscosity of a liquid? | Yahoo Answers
The oil will have a convex meniscus similar to that of mercury. Will the ethylene glycol be pulled up into the tube by capillary action or pushed down below the surface of the liquid in the beaker? Answer Capillary action will pull the ethylene glycol up into the capillary.