The Extraordinary Properties of Water Where there’s life……there’s water!!!

Water threeoxygen hydrogenA water molecule (H 2 O), is made up of three atoms --- one oxygen and two hydrogen. H H O

Water is Polar positively negativelyHaving positively and negatively charged sides. oxygen negativeThe oxygen end “acts” negative hydrogen positiveThe hydrogen end “acts” positive The term “POLARITY” means the molecule has an uneven distribution of electrons

What are the Properties of Water? The Universal Solvent

Properties of Water CohesionCohesion AdhesionAdhesion

Cohesion – “Co” means “With or Together” Attraction between similar substancesAttraction between similar substances (why water is attracted to itself) ( why water is attracted to itself) Due to Hydrogen bondsDue to Hydrogen bonds

Cohesion Produces a surface film on water calledProduces a surface film on water called surface tension that allows insects to walk on water and leaves to float.surface tension that allows insects to walk on water and leaves to float. Surface Tension - a measure of the strength of water’s surfaceSurface Tension - a measure of the strength of water’s surface

Adhesion Attraction of H 2 O to different substances.Attraction of H 2 O to different substances. Due to hydrogen bondsDue to hydrogen bonds Ex:paper towels soak up water, meniscus in a graduated cylinder.Ex:paper towels soak up water, meniscus in a graduated cylinder.

Adhesion Also Causes Water to … Form spheres & hold onto plant leaves Attach to a silken spider web

Both Cohesion and Adhesion Causes Capillary Action Capillary action gives water the ability to “climb” structures

High Specific Heat Amount of heat needed to raise the temp of 1g of H 2 O 1° C.Amount of heat needed to raise the temp of 1g of H 2 O 1° C. Water has a very HIGH specific heat.Water has a very HIGH specific heat. Crucial in temperature stability in living systems to maintain homeostasis.Crucial in temperature stability in living systems to maintain homeostasis.

High Heat of Vaporization Amount of energy to convert 1g water from a liquid to a gas.Amount of energy to convert 1g water from a liquid to a gas. Called vaporization or evaporationCalled vaporization or evaporation

High Heat of Vaporization As water evaporates, it removes a lot of heat with it (cooling effect).As water evaporates, it removes a lot of heat with it (cooling effect). Ex: evaporation of sweat from the bodyEx: evaporation of sweat from the body

Water is Less Dense as a Solid Ice is less denseIce is less dense as a solid than as a liquid – therefore it floats Other materials contract when they solidify, but water expands.

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

Water is a Solvent Solvent: any substance that dissolves other substances.Solvent: any substance that dissolves other substances. Water is a very versatile solventWater is a very versatile solvent Other polar substances dissolve easily in water.Other polar substances dissolve easily in water.

Solution Mixture of 2 or more substances.Mixture of 2 or more substances. Evenly distributedEvenly distributed + +

MIXTURE Materials composed of 2 or more elements or compounds that are physically mixed but not chemically combined.

Hydrophilic (“water-loving” ) substances that dissolve easily in water are known as water soluble. Examples: salts, polar compounds (sugar).

Hydrophobic (means “water-fearing”) substances that do not dissolve easily in water separate and are known as insoluble.. Examples: oils, fats, lipids, waxes. These substances are non-polar.

Acids, Bases and pH One water molecule in 550 million naturally dissociates into a Hydrogen Ion (H + ) and a Hydroxide Ion (OH - ) Hydrogen Ion Hydroxide Ion Acid Base Acid Base H 2 O  H + + OH -

The pH Scale Ranges from 0 to 14 Measures strength of an acid or base by concentration of H + ions and OH - ions. Pure Water has a pH level of 7.

Acids Acids Substance that contains high concentration of H + ions. pH of acids range from 0- 6 Strong acids have a pH of 1-3

Bases Bases OH - ionsSubstance that have lower concentrations of H + ions thus increasing OH - ions Bases have a pH value range from 8 to 14. Strong Bases have a pH of 11 to 14

Buffers Weak acids or bases that react with strong acids or bases to prevent sharp, sudden changes in pH (neutralization). Produced naturally by the body to maintain homeostasisProduced naturally by the body to maintain homeostasis Weak Acid Weak Base