CHEMISTRY COMMUNITY

How does intermolecular forces relate to viscosity and surface tension?

Viscosity is the quality of being "sticky" or very dense. A great example of this is syrup, or honey, which are fluid but very dense. The reason that these viscous liquids are the way they are is because the bonds between the molecules are very strong. Stronger IMF means that liquids are more likely to be viscous. For instance, water has slightly stronger IMF than vegetable oil. When you spill water, it spreads quite a bit. But when you spill oil, it spreads a tad bit faster as the bonds between the oil bonds aren't as strong, so the liquid is able to expand faster. Surface tension, such as when a spider walks on water, depends on IMF strength. Because water has very strong IMF (due to h-bonding), breaking the surface of water takes a bit of energy. However, a spider's weight on top of a pond isn't strong enough to separate bonds between H20 molecules so that the spider sinks. This is because the water is polar and can form strong IMF.

higher surface tension higher viscosity

When molecules have stronger IMF, they are more strongly attracted to each other and therefore do not have as much motion as molecules that are not as attracted to each other. Therefore, molecules with a stronger IMF will have a higher viscosity than molecules with low IMF. The same thing applies to surface tension; when molecules of a liquid have strong IMF, they are more attracted to each other and are less likely to let something break those attractions in the liquid (for example, a fly sitting on water - the water has strong IMF and does not let the weight of the fly break the attractions holding it together). Therefore, stronger IMF leads to a higher surface tension, and weaker IMF leads to lower surface tension.

The result of higher strength intermolecular forces, resulting from the hydrogen bonds between the water molecules, it is harder to break apart those bonds, which causes surface tensions

viscosity and the strength of intermolecular forces are related?

Viscosity and Surface tension are directly related to one another; increase viscosity then the surface tension increases. This is due to the intermolecular forces between molecules. Take a look at water! Water has surface tension that stems from hydrogen bonding between H20 molecules, this means that on a tiny scale, water is viscous! Think of viscosity as a resistance to flow, and surface tension aids in that tiny resistance of movement.

SophiaBarden 3H wrote:Viscosity and Surface tension are directly related to one another; increase viscosity then the surface tension increases. This is due to the intermolecular forces between molecules. Take a look at water! Water has surface tension that stems from hydrogen bonding between H20 molecules, this means that on a tiny scale, water is viscous! Think of viscosity as a resistance to flow, and surface tension aids in that tiny resistance of movement.

This is really well said! You can think of a water bug and how is glides across the surface of water; the surface tension, caused by water molecules linking up strongly due to their H-bonds, of the resistance of the surface to being broken. That same strength in bonding can apply for viscosity as the liquid is so tightly held together it is hard for it to flow.