Chapter: 3 Water

Molecule That Supports All of Life

3/4 of the Earth’s surface Abundance is the main reason the Earth is habitable Figure 3.1

Polarity of water molecules  Hydrogen bonds between molecules  Properties Hydrogen bonds + H  – Figure 3.2

Bonding to neighboring molecules Due to hydrogen bonding Cohesion Bonding to neighboring molecules Due to hydrogen bonding Hydrogen bonds + H  – Figure 3.2

Water conducting cells Transpiration pull water up through the microscopic vessels of plants Water conducting cells 100 µm Figure 3.3

Surface tension Figure 3.4

Water moderates air temperature Absorbs heat from air that is warmer and releasing the stored heat to air that is cooler

Water High Specific Heat Amount of heat absorbed or lost to change its temperature  hydrogen bonds

Evaporative Cooling Allows water to cool a surface

Hydrogen bonds in ice More “ordered” than in liquid water  less dense Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Hydrogen bond Figure 3.5

Since ice floats in water Life can exist under the frozen surfaces of lakes and polar seas

Polar regions of water molecule interact with ionic compounds Solvent of Life Polar regions of water molecule interact with ionic compounds Negative oxygen regions of polar water molecules are attracted to sodium cations (Na+). + Cl – – Na+ Positive hydrogen regions of water molecules cling to chloride anions (Cl–). Cl– Figure 3.6

pH scale pH Scale 1 2 Increasingly Acidic [H+] > [OH–] 3 4 5 6 Increasingly Basic [H+] < [OH–] Neutral [H+] = [OH–] Oven cleaner 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH Scale Battery acid Digestive (stomach) juice, lemon juice Vinegar, beer, wine, cola Tomato juice Black coffee Rainwater Urine Pure water Human blood Seawater Milk of magnesia Household ammonia Household bleach Figure 3.8

Buffers Minimize changes in pH

Acid precipitation Can damage ecosystems More acidic Acid rain 1 2 3 4 5 6 7 8 9 10 11 12 13 14 More acidic Acid rain Normal rain More basic Figure 3.9