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

2. 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. Ex: fats, oils, waxes

3. 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 polar bonds with other polar or ionic molecules.
Ex.: Blood sticks to capillaries

4. Hydrogen Bond Between 2 water molecules = COHESION

5. Polar bond between water and another negative atom = ADHESION

7. High Specific Heat = hydrogen bonds resist changes in temperature.

8. 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)

9. Additional Information
The freezing point is the temperature and pressure at which a liquid material changes from a liquid to a solid. The freezing point of a liquid can be raised or lowered by adding other chemicals to it, such as by adding salt to water. Molecules slow down when forming a solid and pack tightly. Lipids(fats) tend to have a low freezing point.

10. 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)

11. 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.
High Specific Heat: water’s hydrogen bonds resist changes in temp.
Cohesion: water molecules H.B. to each other.
Adhesion: water molecules bond to other polar or ionic things.

12. 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

13. “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)
Colloid: Particles intermediate in size between those found in solutions and suspensions can be mixed such that they remain evenly distributed without settling out. Ex.: Blood, milk, smoke, fog

14. 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.

15. Some compounds form acids or bases.
Acids release a hydrogen ion when it dissolves in water. 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

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

17. Bases remove hydrogen ions from a solution.
They have low hydrogen ion (H+) concentration, high hydroxide ion (OH-) concentration
pH greater than 7
bile pH between 8 and 9
more basic

18. STOP & REVIEW
An _______ releases a __________ ______when it dissolves in water.
An acid releases a hydrogen ion when it dissolves in water.
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