Water and Buffers

Amazing Water!!! Cohesion Surface Tension Adhesion High Specific Heat High Heat of Vaporization Density Universal Solvent

Interaction Between Water Molecules Negative Oxygen end of one water molecule is attracted to the Positive Hydrogen end of another water molecule to form a HYDROGEN BOND

Cohesion Water molecules sticking to each other Hydrogen bonding between individual water molecules Constantly forming and breaking Transpiration in plants, surface tension,…

Surface Tension Measure of how difficult it is to stretch or break the surface of a liquid Important to “water striders” Important in your lungs

Adhesion The clinging of one substance to another Water sticking to glass water clinging to the sides of the xylem in plants helps to counter gravity

Adhesion Causes Capillary Action Gives water the ability to “climb” structures Diameter of tube vs. height? Combined with cohesion =

High Specific Heat The amount of heat required to change 1g of a substance 1 o c. Water will change its temp less when absorbing or losing a given amount of heat Land near large water bodies have milder climates than inland regions Water resists dramatic changes Internal body temps remain constant

High Heat of Vaporization

Heat of Vaporization 580 cal for 1g of H 2 O Evaporation from leaves keeps plant tissues from overheating A panting wolf rids its body of 540 calories of heat energy with each gram of water vapor exhaled. H 2 O’s high heat of vaporization helps moderate Earth’s temp. Quantity of heat a liquid must absorb for 1g of it to be converted from liquid to gas

Santa Barbara 73° Los Angeles (Airport) 75° Pacific Ocean 68° Santa Ana 84° Burbank 90° San Bernardino 100° Palm Springs 106° Riverside 96° San Diego 72° 40 miles 70s (°F) 80s 90s 100s

Density of Water At “normal” temps, water acts like anything else Kinetic Theory of Matter Gets interesting around 4°C

Density of Water As H 2 O cools the molecules slip closer together down to 4 0 C At 0 o C water becomes locked in a crystalline lattice The H-bonds keep the molecules farther apart than expected Ice floats, insulates the water below

Fall/Spring Overturns

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

Water, the Universal Solvent Due to the polar nature of H 2 O Dissolves –Polar substances— alcohol, sugar –Ionic substances—salt, baking soda

pH Scale A measure of the H + concentration in solution, defined as pH = - log H + Each pH unit is a tenfold difference in H + or OH -. Biological systems between 6 – 8 Blood 7.4

Buffers Substances that resist changes in pH when acids or bases are added. Produced naturally by the body to maintain homeostasis Bicarbonate buffer in human body maintains blood pH around 7.4

Quick Quiz

1.Draw a water molecule with labeled atoms and charges. 2.What is the property called that describes water sticking to itself? 3.What makes a solution acidic? 4.What has a higher pH, ammonia or lemon juice? 5.Why do we sweat?

Quick Quiz 1.Draw a water molecule with labeled atoms and charges.

Quick Quiz 1.Draw a water molecule with labeled atoms and charges. 2.What is the property called that describes water sticking to itself?

Quick Quiz 1.Draw a water molecule with labeled atoms and charges. 2.What is the property called that describes water sticking to itself? 3.What makes a solution acidic?

Quick Quiz 1.Draw a water molecule with labeled atoms and charges. 2.What is the property called that describes water sticking to itself? 3.What makes a solution acidic? 4.What has a higher pH, bleach or lemon juice?

Quick Quiz 1.Draw a water molecule with labeled atoms and charges. 2.What is the property called that describes water sticking to itself? 3.What makes a solution acidic? 4.What has a higher pH, bleach or lemon juice? 5.Why do we sweat?