2-2 Properties of Water

Importance of Water Water is the most abundant molecule on earth and in all organisms Liquid water covers 75% of the earth’s surface Without water life as we know it could not exist You would die after about 5 days without water!

The Water Molecule + + H H H2O H H O Two hydrogen atoms, one oxygen atom H H O Water is polar: part of the molecule is slightly positive and part is slightly negative. Hydrogen atoms are slightly positive. Oxygen atom is slightly negative. Oxygen + + H H

Hydrogen bonding Because water is polar it can stick together The hydrogen of one molecule is attracted to the oxygen of another. Cohesion is when water molecules stick together Adhesion is when water sticks to other surfaces

Water is not always pure… Mixture: a substance composed of two or more elements or compounds that are mixed together (not chemically combined). Two types of mixtures form with water Solution: mixture of two or more substances that are evenly distributed Has two parts Solute- what is being dissolved Solvent- substance that the solute is dissolved in Suspension: mixture of water and nondissolved particles

Example of a solution All the ions are evenly dispersed in the water Cl- Cl- Na+ Na+ water Water All the ions are evenly dispersed in the water

Acids, Bases and pH H2O  H+ + OH- Copy down the following notes Acids, Bases and pH H2O  H+ + OH- Water  hydrogen ion + hydroxide ion We can measure how many hydrogen ions a substance has. pH Scale: a measurement system that shows the concentration H+ ions. Scale ranges from 0 – 14 0 – 6.9 = acidic: H+ > OH- 7.0 = neutral (water) H+ = OH- 7.1 – 14 = basic H+ < OH-

Buffers Weak acids or bases that regulated pH Keeps the pH the same Maintains homeostasis There are buffers in our blood