H2O

What is water made of?? Water is made up of 1 oxygen atom bonded to 2 hydrogen atoms. These atoms share electrons to form a water molecule.

Why is water important?? About 75% of human body mass is water Plants contain 70-80% water About 71% of the Earth is covered in water

Why is water important in humans?? Regulates body temperature Makes up major organs Helps clean out wastes Transports nutrients throughout the body. Helps protect our organs from injury.

Water is STICKY (Polar) In each water molecule, the oxygen atom attracts more than its "fair share" of electrons The oxygen end “acts” negative The hydrogen end “acts” positive Which causes the water to be POLAR or STICKY

Opposites Attract Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND

What are the Properties of Water? Properties of water are made possible by H-bonding 1

Properties of H2O made possible by Hydrogen bonding Ice floats… Hydrogen bonds lock H2O molecules into a crystal structure when it freezes, and it leaves empty spaces between molecules. Which makes ice less dense as a solid than as a liquid

Water is Less Dense as a Solid Which is ice and which is water?

Cohesion The attraction of particles of the same substance is cohesion. H2O molecules stick together because of Hydrogen bonding, much the way holding hands keeps a crowd of people together.

Surface Tension The cohesive forces between water molecules form a film on the surface that makes it more difficult for objects to pass through

The attraction of particles of different substances is adhesion. Water will make hydrogen bonds with other surfaces such as glass, soil, plant tissues, and cotton.

Adhesion Capillary action-water molecules will “tow” each other along to move upwards against gravity. Example: transpiration in plants and trees pulls water from the roots towards the leaves.

Adhesion Causes Capillary Action Which gives water the ability to “climb up” through structures.

High Specific Heat Amount of heat needed to raise or lower 1g of a substance 1° C. Water resists temperature change, both for heating and cooling. Water can absorb or release large amounts of heat energy with little change in actual temperature.

In order for water to evaporate, hydrogen bonds must be broken. As water evaporates, it removes a lot of heat with it (cooling effect). This is why sweating cools you down. Water vapor forms a kind of global ‘‘blanket” which helps to keep the Earth warm..

Homeostasis Ability to maintain a steady state and stay constant when conditions change. Water is important to this process because: Insulates us from losing heat b. Resists temperature change Universal solvent – “Likes dissolve likes” Cools us down through sweat e. Ice protects against temperature extremes (insulates frozen lakes)

Properties of Water Hydrogen Bonding Cohesion Adhesion Surface Tension Adhesion Capillary Action High Specific Heat Homeostasis pH of 7

pH of Water is Neutral Waters pH is neutral (not acidic or basic) we are 70% water

Acids, Bases and pH H2O  H+ + OH- One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-) Hydrogen Ion Hydroxide Ion Acid Base H2O  H+ + OH-

Strong Acids have a pH of 1-3 Produce lots of H+ ions Strong Bases have a pH of 11 to 14 Contain lots of OH-ions and fewer H+ ions