KEY CONCEPT Water’s unique properties allow life to exist on Earth.

Life depends on hydrogen bonds in water. Water is a polar molecule. Polar molecules have slightly charged regions. O H _ + Atom: Oxygen Charge: Slightly negative Hydrogen bonds Explain: form between slightly positive hydrogen atoms and slightly negative atoms. (oxygen) Atom: Hydrogen Charge: Slightly positive Nonpolar molecules do not have charged regions.

Hydrogen bonds are responsible for three important properties of water. High Specific Heat: water resists changes in temp. – a lot of energy is required Ex.: Provides stability of temperature for land masses surrounded by water & for the temperature of the human body, & makes it an effective cooling agent. Cohesion: water molecules stick to each other. Ex.: Surface tension holds spiders on water Adhesion: water molecules stick to other things. Ex.: Blood sticks to capillaries

Solid ice is less dense than liquid water Ice floats on water: one of the only solids to float on its liquid form – due to arrangement of water molecules due to charged regions (water is polar). Provides insulation for water below (stays at about 4 degrees C – freezing point is 0 degrees C)

STOP & REVIEW __________ unique properties allow life to exist on Earth. ___________ is a polar molecule. _________ molecules have slightly charged regions. Life depends on ________ ________ in water. They form between slightly positive hydrogen atoms and slightly negative atoms. (oxygen) Nonpolar molecules do not have________ regions. Because of hydrogen bonding, water has what three important properties? _______ _________ ______: water resists changes in temp. ____________: water molecules stick to each other. ____________: water molecules stick to other things.

STOP & REVIEW ANSWERS Water’s____ unique properties allow life to exist on Earth. Water is a polar molecule. Polar molecules have slightly charged regions. Life depends on hydrogen bonds in water. They form between slightly positive hydrogen atoms and slightly negative atoms. (oxygen) Nonpolar molecules do not have charged regions. Because of hydrogen bonding, water has what three important properties? High Specific Heat: water resists changes in temp. Cohesion: water molecules stick to each other. Adhesion: water molecules stick to other things.

Many compounds dissolve in water. A solution is formed when one substance dissolves in another. A solution is a homogeneous mixture. Parts of a solution (Ex. Salt water): Solvents dissolve other substances (Ex.: Water) Solutes dissolve in a solvent. (Ex. Salt) solution

“Like dissolves like.” Polar solvents dissolve polar solutes. (Ex.: sugar water) Nonpolar solvents dissolve nonpolar solutes. Polar substances and nonpolar substances generally remain separate (think of salad dressing – forms a suspension when shaken) http://ed.ted.com/lessons/how-polarity-makes-water-behave-strangely-christina-kleinberg

STOP & REVIEW A ____________is formed when one substance dissolves in another. A solution is a homogeneous mixture. __________dissolve other substances. ___________dissolve in a solvent.

STOP & REVIEW A solution is formed when one substance dissolves in another. A solution is a homogeneous mixture. Solvents dissolve other substances. Solutes dissolve in a solvent.

Some compounds form acids or bases. Acids have high hydrogen ion (H+) concentration, low hydroxide ion (OH- ) concentration pH less than 7 more acidic stomach acid pH between 1 and 3

Neutral solutions have equal hydrogen ion (H+) and hydroxide ion (OH- ) concentration pH: 7 pure water pH 7

Bases have low hydrogen ion (H+) concentration, high hydroxide ion (OH-) concentration pH greater than 7 bile pH between 8 and 9 more basic

STOP & REVIEW An acid has a high concentration of _______ _____. The pH range for an acid is? A neutral solution has a pH of____. A base removes hydrogen ions from a solution and there fore has a _________ hydrogen ion concentration. The ph range for a base is?

STOP & REVIEW ANSWERS An acid has a high concentration of hydrogen ions. The pH range for an acid is? 0-6 A neutral solution has a pH of__7__. A base removes hydrogen ions from a solution and there fore has a low hydrogen ion concentration. The ph range for a base is? 8-14