Some+Properties+of+Liquids

__Liquids__
Intermolecular forces help us understand familiar properties of liquids.

__Viscosity__
Viscosity, the resistance of a liquid to flow, is why liquids flow at different speeds. For example, molasses flows very slowly while water flows easily. This means that the greater the viscosity, the slower the flow. The individual molecules of a liquid interacting with one another affect viscosity, therefore, the attractive forces between molecules cause them to be intertwined. For this reason, it makes sense that viscosity increases with increasing molecular weight. On the other hand, viscosity decreases with increasing temperature because the greater kinetic energy allows molecules to overcome the attractive forces more easily. Viscosity can be determined by measuring the rate of steel spheres falling through the liquid. A sphere would fall slowly if viscosity is increased. Viscosity is recorded in poise (P) or in centipoise (cP).

This picture shows how different liquids have different speeds of fluidity.

__Surface Tension__
Surface tension is the energy required to increase the surface area of a liquid by a unit amount. Surface tension is an affect that causes the surface layer of a liquid to behave like an elastic sheet. The larger the surface layer, the more energy there is, and in order to minimize the energy the liquids assume a shape with the smallest surface area. This is what causes water to "bead up" forming distorted spheres. This occurs due to an imbalance of intermolecular forces at the surface of the liquid. Due to hydrogen bonding, water has a high surface tension. Cohesive forces bind similar molecules to one another (i.e : hydrogen bonding in water). Adhesive forces bind a substance to a surface. Adhesive forces can be seen when water placed in a glass tube sticks to the glass because the adhesive forces overcome the adhesive forces between the water molecules. The curved upper surface in such a glass tube creates a meniscus (a U shape). However, if it had been mercury in the glass, the meniscus would be curved downward because the cohesive forces would be greater than the adhesive forces. Capillary action is when liquids rise up narrow tubes. This is the cause of surface tension reducing the area and therefore pulling the liquid up the tube. The liquid will continue to rise until the cohesive and adhesive forces are balanced by gravity on the liquid. An example of capillary action is when water and dissolved nutrients move up through plants. This picture shows how capillary action works. This pictures represents how the molecules of water are more attracted to the glass than to its own molecules. This is why the water goes up so far in the glass tube. The mercury molecules are more attracted to each other rather than the glass which is why the liquid does not rise up the glass tube very far.

Sources: http://www.chemistryexplained.com/images/chfa_03_img0509.jpg [|http://images.google.com/imgres?imgurl=http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T791087A.gif&imgrefurl=http://encarta.msn.com/media_461551264/Capillary_Action.html&h=328&w=4]