Jenna Zeringue
What Makes Water So Important?

Objective

24. Describe the influence of intermolecular forces on the physical and chemical properties of covalent compounds.
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Characteristics of Water
Formula- H2O
Freezing/Melting Point- 0°C
Boiling Point- 100°C


Heating Curve for Water:
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http://www.bbc.co.uk/schools/gcsebitesize/science/images/gatewaysci_08.gif

Intermolecular Force
The reason for many of water's characteristics is because it is a strong hydrogen bond. A hydrogen bond is an extremely strong dipole-dipole attraction. It occurs only when hydrogen is bonded to oxygen, nitrogen, or fluorine. A hydrogen bond is one of the three intermolecular forces. Intermolecular forces are bonding forces that hold the atoms of a molecule together. The negative end of one water molecule is attached to the positive end of another one to form a hydrogen bond. A normal boiling point is the temperature the liquid is when its vapor pressure is 1 atm. An atm is a pressure measuring unit. Water has a high boiling point because of its hydrogen bond. First, the heat added to the water is just trying to break the hydrogen bond. This uses a lot of energy. Then after it breaks the bonds, then it starts to vaporize the water molecules. A way to graph boiling points and freezing points of substances are heating and cooling curves. Heating curves show how the temperature changes as the substance is heated up. Cooling curves are just the opposite, showing the temperature changes as the substance is cooled.

Surface tension is caused by hydrogen bonds. Surface tension is the attraction of the molecules of a liquid to themselves. Some insects are able to walk on water because it has such a high surface tension.


Super Solvent

​One of the reasons water is so greatly needed on the earth is because it is such a great solvent. A solvent is defined as a substance that is used to dissolve other substances. Without water, waste, fertilizer, etc, would just keep piling up and would never go anywhere. The water is what dissolves the substances and what makes them not keep piling up. The reason water is such a great solvent is because the positive and negative ends of the molecule attach themselves to the negative and positive ends of the molecules in the substance. The force of attraction that the water molecules exert tears apart the molecules of the substance, making them dissolve (Schlager 880).

Common Misunderstanding
For most liquids, their liquid state is less dense than its solid state. This is not true for water. Ice is less dense than water, which is why it floats on top of water. When it freezes, the attractive forces between the water molecules force them to make a crystalline pattern. The crystalline pattern takes up more space than when in the liquid state. As a result, the water expands when forming ice.



Works Cited:
Schlager, Neil, Jayne Weisblatt, and David E. Newton. "Water." Chemical Compounds. 1st. 3. Detroit: Thomson Gale, 2006. Print.
http://www.kentchemistry.com/links/Matter/HeatingCurve.htm