Properties of Water

Water is one of the most important substances on the planet. Not only does it cover 2/3 of the earths surface, but we also use it to clean, drink, and make electricity. Most importantly water makes up 65% of our bodies making it absolutely impossible for us to live with out. There are many properties that differentiate water from other substances.



Polarity
Polarity means that the molecule has a slightly negative and positively charged end. Because water is polar it means that it can dissolve other polar molecules like sugar and ionic compounds like salt. Because the water molecules have a slightly negative and positive side the negative end of on molecule will attached to the positive side of another molecule create hydrogen bonds. Hydrogen bonds are a relatively week bond but they are the reason for adhesion and cohesion.


Adhesion/Cohesion
water is both adhesive and cohesive. Adhesion is how water is sticks to other things. A great example of this is called capillary action. When you place a straw in a glass of water the water climbs up the straw. This shows adhesion and how water sticks to other substances. The opposite of adhesion is cohesion. Cohesion is when water sticks to itself. An example of this is when you see beads or droplets of water. The water likes to stick to itself as oppose to spreading out.


Surface Tension
Surface tension is the tightness across the surface of water that is caused by the polar molecules pulling on one another. If an item is light enough and doesn't beak the surface of the water it will float on top of the water. This is how bugs can sometimes walk on top of water.


Specific Heat
Specific heat is a a characteristic property that determines the amount of heat needed to increase the temperature of a substances one degree Celsius. Water has a very high specific heat. This is why when your at the beach on a very hot day the sand feels very hot but the water stays cool. The sand has a lower specific heat which allows it to heat up quicker while the water remains the same temperature.


Amphotermism:
Water is amphoteric, which means that it can act as either an acid or a base in chemical reactions. According to the Bronsted-Lowry definition, an acid is defined as a species which donates a proton in a reaction, and a base as one which receives a proton. When reacting with a stronger acid, water acts as a base; when reacting with a stronger base, it acts as an acid.


Density/Lattice Formation of Ice:

Water is unlike any other substance because its solid form is less dense then its liquid form. When water is a liquid it is always breaking and creating new hydrogen bonds, so the molecules sit very close together and make the liquid very dense. As the liquid cools down and freezes the molecules don't move around as much making the bonds much more stable. When the liquid freezes the water molecules create lattice formations which are farther apart then how the molecules sit as a liquid make ice less dense than liquid water. 


http://www.youtube.com/watch?v=4auXUSY9c54 <- Click here to watch a youtube video on the properties of water.