Properties of Water

     Today in class we reviewed the properties of water and talked about why those properties make water such a vital substance. The first property about water which makes it important is its high heat capacity, which allows water to absorb a high amount of energy without changing phases, so it moderates the earth's temperature. Water's polarity, the hydrogen atoms being slightly positive and the oxygen atoms being slightly negative, allow for cohesion and adhesion. Cohesion is water's tendency to bond with other water molecules, which leads it to have a high surface tension and leads it to fall in drops instead of in individual molecules. Adhesion is water's tendency to bond with other substances, for instance a paper towel. This property explains why paper towels can soak up water so easily and why water will climb up a straw. This tendency to climb up narrow tubes is called capillary action, which is vital to the ecosystem because it is why water climbs up plants' tubes. Another important property is water's ability to become less dense when it freezes, because the hydrogen bonds expand to have less mass per volume. Because the top layer of water freezes and floats, it allows for marine life to survive underneath the frozen surface.
     Later in class we did an short experiment to demonstrate cohesion. We each had a penny, a pipette, and a beaker of water. We saw how many large drops of water could be placed on the penny before the surface tension was broken. We did this twice and took the average, and then the third time we put the average number of drops and did it a third time using that number. 

A penny experiencing cohesion, 27 drops of water

After the correct number of water drops was on the penny, we observed what would happen if we touched the surface of the water with a toothpick. We observed adhesion, the water went up to meet the toothpick and bonded with it.

The water adhering to the toothpick

 After this we dipped the toothpick in detergent and touched the surface to see what would happen. This broke the surface because detergent is a surfactant, so it broke up the bonds in the water.

After touching the water with the surfactant