The intermolecular forces present in a compound play a role in that Surface tension: Liquids with stronger intermolecular forces tend to have higher surface. Surface tension is an effect within the surface layer of a liquid that causes the layer to behave as an Surface tension is caused by the effects of intermolecular forces at the interface. Solution of a statics problem involving surface tension. Figure 2 illustrates the molecular basis for surface tension by considering the surface tension causes the liquid surface to contract, a force F is needed to move the . We will now use this equilibrium relation to obtain an . PROBLEMS. 1.
Due to a combination of these two effects, long-chain hydrocarbons such as motor oils are highly viscous.
11.E: Liquids and Intermolecular Forces (Exercises)
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.
E: Liquids and Intermolecular Forces (Exercises) - Chemistry LibreTexts
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. 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.
The meniscus will be concave. A water droplet, it's able to have this roughly round shape because all the little water molecules on the surface of the water droplet, and here the surface might even be on the bottom of the water droplet. They are more attracted to each other than they are to the surrounding air, so they're able to form this type of a shape. You might've seen it if you go to a pond or a stream sometimes, so you see some still water.
And let's say, let me do this in blue. So let's say that this is the surface of the water right over here. You might have seen insects that are able to walk on the surface of the water. And I'm not doing a great job at drawing the insects.
They don't look exactly like that. But they can walk on the surface of the water. You might've seen or you might've even tried to do something like put a paperclip on the water.
And even though this thing is actually more dense than the water and you might expect it to sink, but because of the surface tension, which really forms something of a film on top of the water, the thing won't penetrate the surface, so the paperclip will float, unless you were to push on it a little bit and it allow it to puncture the surface, and then it would actually sink, which is what you would expect because it is actually denser. You'd even see this if you were to take a cup, if you were to take a cup and you were to fill it all the way up to the rim and then a little bit higher, it won't immediately overflow.
- Surface tension
- Tension Superficial
It won't immediately overflow. If you're very careful, you'll see that you form a bulge here.
11.4: Intermolecular Forces in Action: Surface Tension, Viscosity, and Capillary Action
And that bulges because those individual water molecules are more attracted to each other than they are to the surrounding air. So that allows for something of a little bulge. Effect of temperature on surface tension Surface tension of water Because intermolecular forces between water molecules are due to hydrogen bonds and these are high energy, surface tension for water is larger than many other liquids.
Comparison of surface tension of water and other liquids Measurement of surface tension There are various methods to measure surface tension of a liquid. One such method consists of a platinum ring placed over the surface of the liquid. The force required to separate the ring from the surface is measured with a high precision scale. Free body Diagram of Dunoy's Ring Surface Tension Statics Surface tension plays an important role in systems where small forces are involved wherever there is a liquid-air interface.
Sample Problem 1 A glass slide is in contact with a water surface along one of its sides as shown in the figure below. What is the magnitude of the force required to overcome surface tension as the slide is lifted from the water surface?