KEY CONCEPT Water’s unique properties allow life to exist on Earth.

Life depends on hydrogen bonds in water. Water is a polar molecule. Polar molecules have slightly charged regions. Nonpolar molecules do not have charged regions O H _ + Atom: Oxygen Charge: negative (-) 1. Weak Hydrogen bond 2. Explain: form between slightly positive and slightly negative atoms---break easily Atom: Hydrogen Charge: positive (+) O H _ + O H _ +

Properties of water related to hydrogen bonds: 1. Capillary action in plants….water moves up roots 2. Cohesion-water likes to bond with other water molecules (are cohesive or tight) 3. Adhesion-water will stick to or adhere to the sides of things

Many compounds dissolve in water. A solution is formed when one substance dissolves in another. Solvents dissolve other substances-usually water Solutes dissolve in a solvent. solution

Some compounds form acids or bases. An acid releases a hydrogen ion when it dissolves in water. high H+ concentration, taste sour… pH = 1-6.9 (1 is strongest acid, 6.9 is weakest) more acidic stomach acid pH between 1 and 3

A neutral solution has a pH of 7. pure water pH 7

A base removes hydrogen ions from a solution. low H+ concentration, taste bitter….are slippery Called basic or alkaline pH = 7.1-14 (7.1 is weakest base, 14 is strongest) bile pH between 8 and 9 more basic