Should we control a chemical that: u Causes excessive sweating and vomiting. u Is a major component in acid rain. u Can cause severe burns in its gaseous state. u Accidental inhalation can kill you. u Contributes to erosion. u Decreases the effectiveness of car brakes. u Has been found in tumors of terminal cancer patients.

What is the chemical? u Dihydrogen monoxide u Otherwise known as H 2 O

Water and the Environment

The Water Planet

Properties Of Water u Be ready and able to discuss several of the following properties. u Focus on definitions and examples. u Review water structure and H-bonds from Chapter 2.

Liquid Water Is Cohesive u Water sticks to water. u Why? Because the polarity of water results in hydrogen bonding.

Liquid Water is Adhesive u Water sticks to other molecules. u Why? Hydrogen bonding.

Water transport in trees uses Cohesion and Adhesion

Water Has A High Surface Tension u The surface of water is difficult to stretch or break. u Why? Hydrogen bonding.

Water Has A High Specific Heat u Specific Heat - the amount of heat needed to raise 1 g of the substance 1 degree C. u Why? Hydrogen bonding.

Heat u Total quantity of kinetic energy due to molecular motion.

Temperature u Measures the average speed of the molecules.

Celsius Scale u Will be used for most of our temperature measurements. u O o C - water freezes u 100 o C - water boils u 37 o C - human body

Water Stabilizes Temperature u Water can absorb and store a huge amount of heat from the sun. u Result - climate moderation u Result - organisms are able to survive temperature changes.

Fig. 3-5 San Diego 72° 40 miles Pacific Ocean 70s (°F ) 80s 90s 100s Santa Barbara 73° Los Angeles (Airport) 75° Burbank 90° San Bernardino 100° Riverside 96° Santa Ana 84° Palm Springs 106°

Water Has A High Heat Of Vaporization u Heat of Vaporization: the quantity of heat a liquid must absorb for 1g of it to convert to a gaseous state.

Evaporative Cooling

Result: u Water cools organisms from excessive heat buildup. u Why? Hydrogen bonding

Water Expands When It Freezes u The distance between water molecules INCREASES from the liquid to the solid form. u Why? u Hydrogen bonding

Solids and Liquids WaterBenzene Floats Sinks

Solid LiquidGas States of Matter

Result u Aquatic life can live under ice.

Hydrophilic Materials u Materials that dissolve in water. u Hydro - water u philic - to like or love u Have ionic or polar regions (polar covalent bonds) on their molecules for H + bonds.

Hydrophobic u Materials that repel water. u Hydro - water u phobic - to fear u Have non-polar covalent bonds. Ex - lipids.

Without Water Life Would Not Be Possible!!

pH Scale u A logarithmic scale for showing H + concentration pH = - log [H + ]

pH Scale

Example: For a neutral solution: [H + ] is or - log or - (-7) or 7

Acids and Bases u Acids: pH <7 etc. u Bases: pH >7 etc. u Each pH unit is a 10x change in H +

Comment u [H + ] + [OH - ] = 14 u Therefore, if you know the concentration of one ion, you can easily calculate the other.

Fig. 3-9 Neutral solution Acidic solution Basic solution OH – H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Neutral [H + ] = [OH – ] Increasingly Acidic [H + ] > [OH – ] Increasingly Basic [H + ] < [OH – ] pH Scale Battery acid Gastric juice, lemon juice Vinegar, beer, wine, cola Tomato juice Black coffee Rainwater Urine Saliva Pure water Human blood, tears Seawater 9 10 Milk of magnesia Household ammonia Household bleach Oven cleaner

Buffers u Materials that have both acid and base properties. u Resist pH shifts. u Cells and other biological solutions often contain buffers to prevent damage.

Summary u Be able to discuss the properties of water. u Be able to measure solution concentrations in Molarity. u Be able to work pH scale questions.