Should we control a chemical that: Causes excessive sweating and vomiting. Is a major component in acid rain. Can cause severe burns in its gaseous state.

Accidental inhalation can kill you. Contributes to erosion. Decreases the effectiveness of car brakes. Has been found in tumors of terminal cancer patients.

What is the chemical? Dihydrogen monoxide Otherwise known as H2O

Chapter 3 Water and the Fitness of the Environment

Question? What molecule Is the most common In living Cells? Water - most cells are 70 - 95% water.

The Water Planet

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

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

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

Water transport in trees uses Cohesion and Adhesion

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

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

Heat Total quantity of kinetic energy due to molecular motion.

Temperature Measures the average speed of the molecules.

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

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

San Bernardino Burbank Santa Barbara 73° 100° 90° Riverside 96° Fig. 3-5 San Bernardino 100° Burbank 90° Santa Barbara 73° Riverside 96° Los Angeles (Airport) 75° Santa Ana 84° Palm Springs 106° 70s (°F) 80s Pacific Ocean 90s 100s Figure 3.5 The effect of a large body of water on climate San Diego 72° 40 miles

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

Evaporative Cooling

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

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

Solids and Liquids Water Benzene Floats Sinks

States of Matter Liquid Gas Solid

Result Aquatic life can live under ice.

Water Is A Versatile Solvent Water will form a solution with many materials. Why? Hydrogen bonding

Solution Homogeneous mixture of two or more substances.

Solvent The dissolving agent. The material in the greater quantity.

Solute The substance that is dissolved. The material in the lesser quantity.

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

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

Solution Concentration Usually based on Molarity. Molarity - the number of moles of solute per liter of solution.

Moles The molecular weight of a substance in grams. One Avogadro’s number of molecules. 6.02 X 1023

One Mole of each Sugar Copper Sulfate Sulfur Mercury Oxide Sodium Chloride Copper

Comment AP Biology students should be able to calculate solutions in Molarity.

Dissociation of Water Water can sometimes split into two ions. In pure water the concentration of each ion is 10-7 M

Adding certain solutes disrupts the balance between the two ions. The two ions are very reactive and can drastically affect a cell.

Acids Materials that can release H+ Example: HCl HCl H+ + Cl-

Acid Rain

Acid Rain

Bases Materials that can absorb H+ Often reduce H+ by producing OH- Example: NaOH NaOH Na+ + OH-

Neutrals Materials that are neither acids nor bases.

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

pH Scale

Example: For a neutral solution: [H+] is 10-7 or - log 10-7 or - (-7)

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

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

Figure 3.9 The pH scale and pH values of some aqueous solutions 1 Battery acid Gastric juice, lemon juice 2 H+ H+ H+ H+ OH– 3 Vinegar, beer, wine, cola OH– H+ H+ Increasingly Acidic [H+] > [OH–] H+ H+ 4 Acidic solution Tomato juice Black coffee 5 Rainwater 6 Urine OH– Saliva OH– Neutral [H+] = [OH–] H+ H+ OH– 7 Pure water OH– OH– H+ Human blood, tears H+ H+ 8 Seawater Neutral solution 9 Figure 3.9 The pH scale and pH values of some aqueous solutions 10 Increasingly Basic [H+] < [OH–] Milk of magnesia OH– OH– 11 OH– H+ OH– OH– Household ammonia OH– H+ OH– 12 Basic solution Household bleach 13 Oven cleaner 14

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

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