Properties of Water Objective: MC.1.B.3 Investigate the properties and importance of water and its significance for life: surface tension adhesion cohesion polarity pH

Vocabulary cohesion –the attraction of same type molecules; in water it causes drops to form. adhesion- the attraction of different type of molecules; water sticks to certain other molecules. surface tension-a combination of adhesion and cohesion properties making it possible for objects or certain organisms to sit on top of water. pH- a 0 to 14 scale that shows how much H+ (hydrogen ion) or OH- (hydroxide ion) are present in a solution; polarity – a property of a molecule causing it to have + and – poles; water has polarity. capillary action- a property of water that is caused by adhesion and cohesion; it allows water to rise against gravity in narrow tubes such as up a plant.

Oceans cover 3/4th of the Earth’s surface Oceans cover 3/4th of the Earth’s surface. Water is the single most abundant compound in most living things.

Water can be found naturally in all three states.

Why do frozen water bottles sometimes explode?

Why does ice float? ICE

Water floats because… As water freezes, it expands outward. This makes it less dense than liquid water. Most liquids contract. Water is different. As you know, from Physical Science, the more dense object always sinks! http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg

How would life in this pond be different if frozen water sank instead of floated? Tie your answer to a concept we learned in Ecology.

Water http://vimeo.com/37064053

The Water Molecule A water molecule (H2O) is neutral. Water is formed from the elements of Hydrogen and Oxygen.

Water Structure Unequal Sharing of electrons produces a polar molecule. Sad Reindeer  MICKEY MOUSE http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg Stop at 2:10 minutes

Water’s polarity gives it some unusual characteristics! Hydrogen Bonds Cohesion Adhesion Surface Tension Capillary Action Solvent pH High specific heat

1. Hydrogen Bonding Hydrogen bonding happens in polar molecules. These are bonds between electronegative atoms such as Oxygen (O), Nitrogen (N) or Fluorine (F) and Hydrogen (H). Stronger than van der Waals but weaker than covalent and ionic bonds. A single water molecule can make as many as four hydrogen bonds!

2. Cohesion Due to the Hydrogen bonds the water molecules stick together slightly, which is called cohesion.

3. Adhesion When water molecules stick to other molecules, we call it adhesion. Ex: the walls of tubes. http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg Start: 2:10 Stop 2:31

4. Surface Tension Water’s hydrogen bonds also give it a strong surface tension. Surface tension is how difficult it is to break the surface of a liquid. http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg Stop at 2:50

5. Capillary action Caused by adhesion and cohesion; It allows water to rise against gravity in narrow tubes such as up a plant. Trees and plants depend on this force to allow them to transport water from roots to their leaves.

6. It is a great solvent A solute is any substance that is dissolved. A solvent is the dissolving agent. Water makes a great solvent because of its polarity. It has the ability to attract both positive and negative ions.

Solvent and Solute

7. pH Acids and Bases H20 -> H+ + O H- Water yields Hydrogen hydroxide The Ph scale: Solutions above 7 are basic because they have more OH- ions. Solutions below 7 are acidic because they have more H+ ions. Buffers are solutions that are neutral or are barely acidic or basic

8. High specific heat Water absorbs a lot of heat before it changes temperature. This is how oceans, lakes and water vapor help regulate temperature on the Earth

What affect do oceans have on the earth’s temperature?