Water

Water

O and H are bonded together by Covalent Bonds O and H share electrons but they are closer to the Oxygen This makes the O slightly negative - and the H slightly positive + Water is a POLAR Molecule. The O is a little -, the H is a little +. The positive end (H) of one water molecule attracts the negative end (O) of another water molecule, until all the water molecules are connected.

Density

Solid water is less dense than liquid water Water is the only substances that expands when it freezes. Ice is less dense than liquid water - Ice FLOATS If ice sank... all life in ponds, lakes and oceans would be crushed! Ice on top insulates lakes and oceans from colder air temperatures.

High Heat of Vaporization

Water absorbs heat when it evaporates. When organisms sweat - they cool off.

Universal Solvent

Water dissolves most substances (good solvent). Water inside the cells and body can carry nutrients and waste around. Water is used to "wash" - it dissolves stuff

Capillary action

water moves up thin tubes The thinner the tube, the higher the water moves. As water crawls up a tube, it pulls other water molecules through cohesion - crawl up and pull-

Hydrogen Bond

weak attraction between the slightly negative oxygen of one molecule, and the slightly positive hydrogen of another H-Bonds are weak - Draw the charge and the H-bonds between these water molecules - use dotted lines.

Solvent

what dissolves the solute (most common: water)

Solute

what is dissolved (salt, sugar, etc.)

Adhesion

Adhesion: attraction between molecules of different substances. Water loves other substances. Adhesion explains why: - A meniscus forms in graduated cylinders/tubes. (water sticks to the glass and "crawls up") When water moves up a thin tube it is called Capillary Action. Water moves up against gravity!!! Water moves from the roots to the top of plants through small vessels called xylem.

Why is water so important for life?

Cohesion and adhesion give water High Surface Tension 2. Water can move up through small tubes against gravity = Capillarity 3. Water dissolves most substances (Universal Solvent). 3. Water is able to absorb large amounts of heat. Stabilize temperatures 4. Water absorbs heat when it evaporates. Organisms can cool off. 6. Solid water (ice) is less dense than liquid water. Water expands when it freezes and floats.

Cohesion

Cohesion: attraction between molecules of the same substance. Water is very cohesive because water molecules are attracted to each other by H-bonds. Molecules hold on to each other tightly and create high surface tension. Cohesion explains why insects can walk on water, or why water makes drops.

How do water molecules stick together?

Hydrogen Bonds

High Specific Heat

It takes a long time for water to heat up and cool off. Water absorbs large amounts of heat and then releases the heat slowly. This is why oceans stabilize temperatures. Areas near the ocean stay cooler in the summer and do not get as cold in the winter.

pH of a solution: 0 -14

pH: Measures how acid or basic a solution is. Measures the concentration of H+ ions in the solution . Acids release more H+. Bases release more OH- 0=Very Acid 7=neutral 14=Very Basic