The most important inorganic compound for living organisms! Properties of Water The most important inorganic compound for living organisms!

Water is POLAR! Water has an unequal distribution of charges…the O atom has a (-) charge & each H atom has a (+) charge. Polarity refers to the property of having 2 opposite poles. HOW DOES THIS RELATE?

Hydrogen Bonds The oppositely charged ends of a water molecule can form weak interactions with each other known as HYDROGEN BONDS! Opposites Attract!

Cohesive An attraction of molecules of the same substance Water can “stick” to itself….surface tension! Explains why some insects can “walk on water”

Adhesive An attraction between molecules of different substances. Allows for capillary action….draws water out of roots up into the stems.

Water has a high heat capacity…what does that mean? Water is able to absorb large amounts of heat. As a result, lakes and oceans stabilize air and land temperatures.

Ice floats? Yes, Water is more dense as a liquid than a solid! Prevents lakes & ponds from freezing solid…life can survive at the bottom Also allows for mixing of nutrients in water

Universal Solvent Most all of our chemical reactions take place in SOLUTIONS….comprised of a solute (the substance dissolved) and a solvent (the substance in which the solute dissolves)…water is the greatest solvent on Earth!

In summation, Water is essential for life on Earth!

pH and the Importance to Life

Water hydrogen hydroxide Acids vs. Bases Produces H+ ions in solution and have pH values less than 7 Produces OH- ions in solution and have ph values greater than 7 H2O  H+ + OH- Water hydrogen hydroxide Pure water is NEUTRAL and has a pH of 7.

pH Scale: Goes from 0-14 - 0-6 = ACID 7 = NEUTRAL 8-14 = BASE NOTE: Every # is a factor of 10X!

Why do we care in BIOLOGY? Stomach is acidic (help break down food) Soil pH is key to plant life (Hydrangeas change color based on pH of soil) Acid Precipitation (affects both aquatic life and plants) Most biological processes take place in pH close to NEUTRAL (6.5-7.5), some slightly basic or acidic Enzymes function at certain pH

What is a buffer? Mixtures that can react with acids or bases to keep the pH within a certain range EXAMPLE: You have an upset stomach (ACIDIC), what do you take to help NEUTRALIZE the stomach acid?? A BASE!!!! (Tums!)

Let’s Watch!! http://www.youtube.com/watch?v=zTLiJE-j1-I&feature=PlayList&p=37CBB4FE24FC3885&playnext=1&playnext_from=PL&index=42