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

2.2 Properties of Water O HH _ ++ Life depends on hydrogen bonds in water. Water is a polar molecule. –Polar molecules have slightly charged regions. – Nonpolar molecules do not have charged regions. Ex: fats, oils, waxes 1.Hydrogen bonds 2.Explain: form between slightly positive hydrogen atoms and slightly negative atoms. (oxygen) Atom: Oxygen Charge: Slightly negative Atom: Hydrogen Charge: Slightly positive

2.2 Properties of Water Hydrogen bonds are responsible for three important properties of water. –High Specific Heat: hydrogen bonds in water resist changes in temp. – a lot of energy is required to disrupt the hydrogen bonds. –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 form hydrogen bonds with each other. –Ex.: Surface tension holds spiders on water –Adhesion: water molecules form hydrogen with other polar or ionic molecules. –Ex.: Blood sticks to capillaries

2.2 Properties of Water Hydrogen Bond Between 2 water molecules = COHESION

2.2 Properties of Water Hydrogen Bond between water and another negative atom = ADHESION

2.2 Properties of Water

High Specific Heat = hydrogen bonds resist changes in temperature.

2.2 Properties of Water 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)

2.2 Properties of Water STOP & REVIEW __________ unique properties allow life to exist on Earth. Water’s____ unique properties allow life to exist on Earth ___________ is a polar molecule. Water is a polar molecule. _________ molecules have slightly charged regions. Polar molecules have slightly charged regions. Life depends on ________ ________ in water. They form between slightly positive hydrogen atoms and slightly negative atoms. (oxygen) Life depends on hydrogen bonds in water. They form between slightly positive hydrogen atoms and slightly negative atoms. (oxygen)

2.2 Properties of Water STOP & REVIEW Nonpolar molecules do not have________ regions. Nonpolar molecules do not have charged regions. Because of hydrogen bonding, water has what three important properties? –_______ _________ ______: water resists changes in temp. –____________: water molecules hydrogen bond to each other. –____________: water molecules hydrogen bond to other polar or ionic things. Because of hydrogen bonding, water has what three important properties? –High Specific Heat: water’s hydrogen bonds resist changes in temp. –Cohesion: water molecules H.B. to each other. –Adhesion: water molecules H.B. to othe rpolar or ionic things.

2.2 Properties of Water 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) –Happens because water is polar and exhibits the property of adhesion (can stick to other things). solution

2.2 Properties of Water “Like dissolves like.” –Polar solvents dissolve polar solutes. (Ex.: salt water) –Nonpolar solvents dissolve nonpolar solutes. (wax and oil) –Polar substances and nonpolar substances generally remain separate (think of water and oil) behave-strangely-christina-kleinberg

2.2 Properties of Water STOP & REVIEW A ____________is formed when one substance dissolves in another. A solution is a homogeneous mixture. A solution is formed when one substance dissolves in another. A solution is a homogeneous mixture. –__________dissolve other substances. –Solvents dissolve other substances. –___________dissolve in a solvent. –Solutes dissolve in a solvent.

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

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

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

2.2 Properties of Water STOP & REVIEW The pH range for an acid is? The pH range for an acid is? 0-6 A neutral solution has a pH of____. A neutral solution has a pH of__7__. A ______ removes hydrogen ions from a solution. A base removes hydrogen ions from a solution. The ph range for a base is? The ph range for a base is? 8-14