My science fair project is on the surface tension of water and what affects the surface tension of water. The question that I am going to ask is how does temperature and salinity of water affect the surface tension of the water. My hypothesis is that the colder and the saltier that the water is, the stronger that the surface tension of the water will be. Some of the background research that I have done has explained to me that the surface tension of water is a property of a liquids surface that can cause it to resist external forces.
Surface tension is caused by the property of cohesion which is intermolecular attraction between two or more similar molecules. The molecules on the surface of the liquid in this case water have no molecules on top of them and are pulled inward which creates internal pressure of the liquid which causes the surface to contract to the minimal area possible.
An easier way to look at it is like this, a molecule that is in contact with an acquaintance is in a lower state of energy than if it were alone so there for the interior of molecules have as many neighbors as they can possibly have but the outer molecules that are on the surface do not try to do such and they have a much higher energy because of it.
I also found that surface tension is measured in forces per unit length and stated in newton’s per meter but it can also be measured as joules per square meter if it is in the use of thermodynamics where it is expressed as work done per unit of area where it is stored as potential energy which is the energy that a piece of matter has because of its position or because of its arrangement of parts.
Water molecules that are at the surface are like a frozen stretched out sheet of optimally bonded molecules, as the molecules shake into the minimal energy configuration.
Each water molecule which consists of one oxygen and two hydrogen’s also known as H2O can form hydrogen bonds with four other water molecules. The way that surface tension forms is first that the number of hydrogen bonds of water molecules on the surface is maximized as much as possible then entropy which is a statistical measure of the disorder of a closed system is maximized by minimizing the amount of water molecules on the surface. Lastly tension on the surface of the water is increased as the high energy molecules move to the low energy regions of the fluid.
The air outside of the surface film is hydrophobic which means that it cannot form a hydrogen bond that is why the water molecules cannot form hydrogen bonds with the air because air is composed of largely spaced gas molecules. The surface of the water does come into contact with the air though but it happens rarely and when it does the nitrogen and oxygen molecules collide with the water and no bonds are formed so the gas molecules return to freely float around the air. The interface boundary of the liquid in this case water is formed by the difference in attractions between liquids and gases.
The measurement of surface tension of a liquid is really just a measurement of forces because of its various properties of balancing the forces which create surface tension. Surface interactions are very critical in analyzing the behavior of liquids. Modern methods of surface tension measurement can be digital, like the Goniometer method, which measures surface contact angle and the capillary pressure between two fixed fluids, like water and air. This method measures pressure differences of the two fluids and compares the pressure to the shape of the liquids surface. There are very many uses of surface tension measurement.
Surface interactions are a major process in examining the behavior of liquids. The relationship between the pressures involved in surface tension measurement is very important in defining their properties. There are several different forms of surface tension which means that there are many different ways of measuring surface tension in terms of data applications and analyzations. The most commonly known way is called the du Nouy ring method developed in 1925 by Pierre Lecomte du Nouy which is a method which uses a force to lift a platinum ring from the surface of a liquid and measuring the amount of force that was required to do so.
I did much research into the ideas and theories behind surface tension and what I found most interesting was the different ways of measuring the surface tension and how the surface tension cannot bond with air. Bibliography: * Coffey, J. (n. d. ). Surface Tension. Universe Today — Space and astronomy news. Retrieved November 9, 2011, from http://www. universetoday. com/81655/surface-tension/ * Surface tension. (n. d. ). Attension – Precision made simple. Retrieved November 9, 2011, from http://www. attension. com/surface-tension. aspx * Viscosity-Surface Tension-properties of liquid. (n. d. ). Welcome to City Collegiate.
Retrieved November 9, 2011, from http://www. citycollegiate. com/viscosity. htm * ayers, a. (n. d. ). What Is Surface Tension? : Hydrogen Bonds, Organized Water and Maximized Entropy | Suite101. com. Suite101. com: Online Magazine and Writers’ Network. Retrieved November 9, 2011, from http://www. suite101. com/content/what-is-surface-tension-a133497 * mcdonagh, b. (n. d. ). Surface Tension Measurement – ATA Scientific Articles. Particle Size Analyser, Rheometers, CD Spectropolarimeters – ATA Scientific. Retrieved November 9, 2011, from http://www. atascientific. com. au/blog/2010/06/21/surface-tension-measurement//