“Properties of Water”

Water has a very simple atomic structure. This structure consists of two hydrogen (H) atoms bonded to one oxygen (O) atom. The unique way in which the hydrogen atoms are attached to the oxygen atom causes one side of the molecule to have a negative charge and the area in the opposite direction to have a positive charge. The hydrogen side of the water molecule has a slight positive charge. The oxygen side of the water molecule has a slight negative charge. This polarity causes molecules of water to be attracted to each other forming strong molecular bonds.

HYDROGEN BONDS PROPERTIES of water due to POLARITY cohesive behavior resists changes in temperature high heat of vaporization expands when it freezes universal solvent

polar molecule a molecule that has electrically charged areas molecule with a slightly positive end and a slightly negative end as a result of electrons being shared unequally forming an attraction that holds the molecules together

between water molecules to form drops and remain cohesion attractive force between water molecules that allows water to form drops and remain a liquid at room temperatures 

between water molecules adhesion                attractive force between water molecules and other solid substances

the water runs along the glass and does not fall straight. Caused by adhesion the water runs along the glass and does not fall straight.

capillary action the combined force of attraction between water molecules and with molecules of other surrounding materials process that moves water through narrow tubes or small porous spaces 

capillary action

Capillary action is related to the adhesive properties of water. You can see capillary action 'in action' by placing a straw into a glass of water. The water 'climbs' up the straw. What is happening is that the water molecules are attracted to the straw molecules. When one water molecule moves closer to the straw molecules the other water molecules (which are cohesively attracted to that water molecule) also move up into the straw. Capillary action is limited by gravity and the size of the tube. The thinner the tube or straw, the higher up capillary action will pull the water.

EXAMPLES: capillary action adhesion + cohesion = capillary action water taken up by roots All due to hydrogen bonding!

the tightness across the surface of water surface tension                the tightness across the surface of water due to the cohesive properties of water that is caused by the polar molecules pulling on one another

Water behaves as if covered by an invisible skin. Water has a greater surface tension than most other liquids because hydrogen bonds among surface water molecules resist stretching or breaking the surface. Water behaves as if covered by an invisible skin. Some animals can stand, walk, or run on water without breaking the surface. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

buoyancy              the upward force on an object produced by the surrounding fluid (liquid or gas) in which it is fully or partially immersed  the net upward force is equal to the weight of the fluid displaced by the object

universal solvent Water is considered to be the universal solvent. More substances will dissolve in water than any other liquid.  This includes other polar substances (such as sugar) and ionic compounds (such as salt).    

specific heat                amount of heat energy required to raise the temperature of 1 kg of a substance by 1 degree Celsius

Water’s high specific heat ensures slow temperature changes. Water can absorb large amounts of heat energy before it begins to get hot.

Water’s high specific heat ensures slow temperature changes. Water releases heat energy slowly when it cools.

Water is Less Dense as a Solid Ice is less dense as a solid than as a liquid (ice floats) Liquid water has hydrogen bonds that are constantly being broken and reformed. Frozen water forms a crystal-like lattice whereby molecules are set at fixed distances. 1

Water is Less Dense as a Solid Which is ice and which is water? 1

Water is Less Dense as a Solid Ice 1

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-

The pH Scale Indicates the concentration of H+ ions Ranges from 0 – 14 pH of 7 is neutral pH 0 up to 7 is acid … H+ pH above 7 – 14 is basic… OH- Each pH unit represents a factor of 10X change in concentration pH 3 is 10 x 10 x 10 (1000) stronger than a pH of 6

Acids Strong Acids have a pH of 1-3 Produce lots of H+ ions

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

Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH (neutralization). Produced naturally by the body to maintain homeostasis Weak Acid Weak Base