Water

Water  2 Hydrogen atoms + 1 Oxygen atom covalently bonded (polar)  Makes up 70-95% of living things, covers 75% of Earth  DRAW and LABEL this in your notes

Properties of Water  Cohesion created by the constant forming and reforming of hydrogen bonds between water molecules created by the constant forming and reforming of hydrogen bonds between water molecules creates a more structurally organized liquid creates a more structurally organized liquid Enables water to move against gravity Enables water to move against gravity

Forming Hydrogen Bonds  Draw this in your notes!!!

Properties of Water  Adhesion Created by the clinging of one substance to another Created by the clinging of one substance to another water adheres to the walls of vessels to counter the downward pull of gravity water adheres to the walls of vessels to counter the downward pull of gravity

Properties of Water  Surface Tension A measure of how difficult it is to stretch or break the surface of a liquid A measure of how difficult it is to stretch or break the surface of a liquid Water has a greater surface tension than most other liquids Water has a greater surface tension than most other liquids

Properties of Water  Moderating Temperatures Stabilizes air temperature by absorbing heat from warmer air and releasing the stored heat to the cooler air Stabilizes air temperature by absorbing heat from warmer air and releasing the stored heat to the cooler air Used as the basis for Celsius scale to indicate temperature Used as the basis for Celsius scale to indicate temperature Water freezes at 0 o and boils at 100 oWater freezes at 0 o and boils at 100 o

Properties of Water  Specific Heat Amount of heat absorbed or lost for 1g of substance to change temperature of water 1 o Amount of heat absorbed or lost for 1g of substance to change temperature of water 1 o Water’s specific heat is 1 cal/g/ o C (10 times that of iron) Water’s specific heat is 1 cal/g/ o C (10 times that of iron) Must absorb or release a relatively large quantity of heat for temperature to change Must absorb or release a relatively large quantity of heat for temperature to change Organisms made mostly of water resist temperature changes Organisms made mostly of water resist temperature changes

Evaporative Cooling  Vaporization (evaporation): transformation from liquid to gas Helps to protect terrestrial organisms from overheating (sweating) Helps to protect terrestrial organisms from overheating (sweating) Contributes to stability of temperatures in lakes and ponds Contributes to stability of temperatures in lakes and ponds Helps moderate climate on Earth Helps moderate climate on Earth

Heat of Vaporization  the quantity of heat that must be absorbed for 1g of liquid to be converted to a gas  Water’s is high at 580 cal/g Due to large amount of heat needed to break hydrogen bonds Due to large amount of heat needed to break hydrogen bonds

Ice  Solid water (ice) is less dense than liquid water therefore, ice floats Caused by hydrogen bonds forming between water molecules and becoming stable Caused by hydrogen bonds forming between water molecules and becoming stable

Parts of Solutions  Solution: a liquid mixture of 2 or more substances  Aqueous solution: liquid in which water is the solvent  Solvent: dissolving agent of solutions  Solute: substance being dissolved

Water “Loving”  Hydrophilic: any substance with an attraction to water Substance does not have to dissolve Substance does not have to dissolve EX: cotton EX: cotton

Water “Non-Loving”  Hydrophobic: any substance which repels water Ex: vegetable oil

Water Molecules  A water molecule can dissociate into two parts: Hydrogen ion: H + Hydrogen ion: H + Hydroxide ion: OH - Hydroxide ion: OH -

pH  Acids: substances which increase H + concentration of a solution Ex: Nitric Acid: HNO 3 Ex: Nitric Acid: HNO 3  Bases: substances which increase OH - concentration of a solution Ex: Sodium hydroxide: NaOH Ex: Sodium hydroxide: NaOH  Buffers: substances that minimize changes in pH

pH Scale  Range from 0-14 Acids are 0-6 Acids are 0-6 Ex: gastric juice 2, urine 6Ex: gastric juice 2, urine 6 Bases are 8-14 Bases are 8-14 Ex: ammonia 13, sea water 8.5Ex: ammonia 13, sea water 8.5 Neutrals are at 7 Neutrals are at 7 Ex: Pure water, human blood is very closeEx: Pure water, human blood is very close

The End  Any Questions????