Properties of Water

Recently in Biology we have been studying the properties of water, and we did a lab focusing on three properties.  In the lab, we did a trial on the surface tension in water, using pennies.  The experiment required you to place as many droplets as you could onto a single penny without them falling off.  I learned that a penny can hold quite a few droplets because of surface tension.  In the next experiment we had to place a drop of water onto a piece of wax paper.  Using a toothpick, we had to split the drop of water in half.  As we were attempting to split it in half, the tiny droplet would not split; but it would simply just slide along the wax paper staying together which helped us examine the cohesion process.  The last part of the lab we experimented with a beaker of water, a string, and an empty beaker.  In this lab, Kelsea and I had to figure out how to take the water from the full beaker and run it down the  string to the empty beaker.  We figured out that in order to get the water to travel down the piece of string, we had to change the position of how the water was poured.  We finally discovered that if you hold the empty beaker directly below the string and beaker of water, and the full beaker, the water should travel directly down the string into the empty beaker.
While watching and observing the videos Water and Life: Overview and The Nature of Water, I learned many different things, along with definitions of certain words.  I observed that water is a solvent meaning it's chemical composition does not change when dissolved into another substance.  The molecular formula of water is H20 which means that the chemical composition of water consists of one oxygen atom and two hydrogen atoms.  I also found out there are two types of polarity which are bond polarity and molecular polarity.  Water exemplifies bond polarity because the oxygen atom and hydrogen atom are not evenly distributed among the two atoms.  They are closer to the oxygen atom than they are the hydrogen atom.  Water also shows molecular polarity because of it's bent shape.  Without a net "pull" in a direction, the molecule will not be polar.

                                                as shown above water molecules are bent




WORDS OF KNOWLEDGE

*Adhesion-The attractive force between molecules in one phase and different molecules in another phase.

*Cohesion-The attractive force between similar molecules in the same phase

-Sum of hydrogen bonds

*Hydrogen Bond-A weak to moderate attractive force between a hydrogen atom bonded to oxygen, nitrogen, or fluorine, and an oxygen, nitrogen, or fluorine atom on another atom.

-Usually represented by dotted lines

*Hydrophilic-Water-loving; easily dissolves in water

*Hydrophobic-Water-fearing; doesn’t dissolve in water

-ex: oil

*Polar Covalent Bond- A molecule where electrons are shared between the two atoms.  One atom is more electronegative than the other which causes the electrons to pull closer to it.  Partial charges are formed which creates dipole.

*Solvent-A liquid which dissolves another substance without any change in its chemical composition.

*Specific Heat-The amount of heat needed to raise the temperature of a 1-gram sample of a substance by 1 degree Celsius

*Surface Tension-The energy needed to increase the surface area of a liquid by a given amount.

*Electronegativity-The tendency of an atom in a bond to attract shared bonding electrons