Surface Tension of Water Research

Water (H2O) is a good solvent because it is partially polarized. The hydrogen ends of the water molecule have a partial positive charge, and the oxygen end of the molecule has a partial negative charge. This is because the oxygen atom holds on more tightly to the electrons it shares with the hydrogen atoms. The partial charges make it possible for water molecules to arrange themselves around charged atoms (ions) in solution, like the sodium (Na+) and chloride (Cl−) ions that dissociate when table salt dissolves in water.

Surface Tension: The measure of how difficult it is to stretch or break the surface of a liquid.

Attraction between water molecules which allows insects and other objects to float a top the water

When an object falls onto the surface, it has to push the water molecules apart. If the effect of the weight of the object is insufficient to match the attractive forces between molecules in the surface layer, the object will not enter the surface.

Hydrogen bonds contribute to a property of water called cohesion or the tendency of water molecules to stick together.

In the third stage of this experiment, the density of a liquid was determined and compared to known standards. A 100ml beaker was filled to about half-full with room-temperature distilled water. The temperature of the water in ◦C was recorded in order to compare to known standards later. A 50ml beaker was then weighed on a scale in order to determine mass and recorded. A sample of the distilled water with an exact volume of 10ml was then placed in the 50ml beaker using a volumetric pipette. The 50ml beaker with the 10ml of water was then weighed again and the initial mass of the beaker was subtracted from this mass to obtain the mass of the 10ml of water. With the volume and the mass of the water now known, density was calculated using d = m/V and recorded in g/ml. This process was then repeated to check for precision and compared to standard values to check for accuracy. Standard values were obtained from CRC Handbook, 88th Ed.

The force of buoyancy is important in many different areas, and especially in the making of ships. The surface area that is touching the water of the ship is very large, due to the shape of the hull, and that, beside the density of the ship, is what keeps the ship

In the article, a student in Brookville, NY asks about the behaviors of water—specifically, why it would become a sphere in space when it doesn’t have a shape. The author answers this by giving her a thorough explanation. She states that unlike liquids on Earth, which are content with staying at the “bottom of a glass”, liquids in space react differently in the nearly weightless environment of the space shuttles. Molecules in liquid water are mutually attracted towards one another, but, they do not mind breaking this bond. According to the author, that is the reason liquid water can take the shape of vessel it’s poured into. However, the water molecules at the surface are only attracted to other water molecules below them and sideways to them

Another factor is the Momentum Thickness, ϴ. It is defined as the thickness of a layer of freestream fluid carrying a momentum flow rate equal to the reduction in momentum flow rate caused by the formation of the boundary layer. Closer to the surface of the object, the flow is slower. This means that the momentum is also slower. ϴ is a measurement of the compensation that makes us the momentum flow rate that was lost due to the formation of the boundary layer. The momentum thickness is useful in determining the skin friction drag on a surface. [5] When deriving this equation it is assumed the flow is incompressible and steady. Momentum Thickness is an indication of Drag.

In water, an object has to be less dense than water to float. The same goes for cereal, which is less dense than milk and allows them to float. In liquids, cohesive forces are strong enough to keep molecules together but weak enough to slide past each other. Fluids with high viscosity have strong cohesive forces and fluids with low cohesive forces have weak cohesive forces. Viscosity can be calculated by its flow rate.

Tension is the state of being stretched tight. For example if you have a piece of paper and you try to stretch it won’t this is called tension. If you cut out the bottom of a cup the tension is gone. If you try to replace the bottom of the paper cups with something else for example, sand you can also see that the sand replaces the bottom of the cups. The sand replaces the base to make it even stronger than it was before. The sand’s replacing the tension which causes the cups to stretch back out again and make this experiment a lot more interesting.

Intermolecular Forces: Evaporation and Surface Tension Purpose: The purpose of this laboratory experiment to learn about experimentally determines the temperature changes caused by evaporation of various liquids and relate this date to strength of the Intermolecular Forces. Principles: Predict the rate of evaporation based on the types of intermolecular attractions between molecules. Draw Lewis structures of simple organic molecules. Understand how intermolecular attraction relates to physical properties such as boiling Raw date: Substance Formula tmax (°C) tmin (°C) t (tmax–tmin) (°C) methanol CH3OH 23.76 2.83 20.93 ethanol C2H5OH 28.89 12.37 16.57 1-propanol C3H7OH 27.19 13.50 13.69 1-butanol C4H9OH 28.03 16.78 11.25 n-heptane C7H16

[2] Kinnas, Dynamic Viscosity of Air as a Function of Time, http://www.ce.utexas.edu/prof/kinnas/319lab/Book/CH1/PROPS/GIFS/dynair.gif Accessed on 15/04/2013

Weather a surface is hydrophobic or hydrophilic largely depends upon surface chemistry. Each and every surface has energy which is proportional to area .For liquids surface tension is identical to surface energy. And we know everything moves towards reducing its energy therefore drops tend to be spherical. But what about droplets on a solid surface. Drops form an inverted cup like structure and the angle made by drop surface with the solid surface is called the contact angle. Every surface has Surface Energy. There is surface energy or surface tension between air-solid-liquid. Contact angle is defined as the equilibrium angle made by liquid surface with the solid surface.Young’s equation describes the force balance between the interfacial tensions formed at the solid–liquid–vapor contact line.

The purpose of this module is to investigate hydrostatic forces on a plane surface under partial and full submersion.