1. How many mm is in 1 km?
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2. 2-2 Properties of Water
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3. A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.
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4. Water Molecule
The unequal sharing of electrons causes the water molecule to be polar. The hydrogen end of the molecule is slightly positive and the oxygen end is slightly negative.
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5. Hydrogen Bonds
Because of their partial positive and negative charges, polar molecules can attract each other.
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6. Cohesion is an attraction between molecules of the same substance
Cohesion is an attraction between molecules of the same substance. Because of hydrogen bonding, water is extremely cohesive.
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7. Adhesion is an attraction between molecules of different substances.
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8. Solutions and Suspensions
A mixture is a material composed of two or more elements or compounds that are physically mixed but not chemically combined.
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9. Two types of mixtures can be made with water
solutions
suspensions
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10. Solutions All the components of a solution are evenly distributed throughout the solution. solute—the substance that is dissolved. solvent—the substance in which the solute dissolves.
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11. When a crystal of table salt is placed in warm water, sodium and chloride ions are attracted to the polar water molecules.
Na+
Cl -
Water
When an ionic compound such as sodium chloride is placed in water, water molecules surround and separate the positive and negative ions.
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12. Suspensions 
Some materials do not dissolve when placed in water but separate into pieces so small that they do not settle out easily.
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13. Acids, Bases, and pH
A water molecule is neutral, but can react to form hydrogen and hydroxide ions.
H2O   H+ + OH-
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14. The pH scale 
Chemists devised a measurement system called the pH scale to indicate the concentration of H+ ions in solution.
The pH scale ranges from 0 to 14.
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15. At a pH of 7, the concentration of H+ ions and OH- ions is equal.
The pH Scale
At a pH of 7, the concentration of H+ ions and OH- ions is equal.
Sea water
Human blood
Pure water
Milk
Normal rainfall
The concentration of H+ ions determines whether solutions are acidic or basic.
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16. Acids An acid is any compound that forms H+ ions in solution.
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17. Bases
A base is a compound that produces hydroxide ions (OH- ions) in solution. 
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18. Buffers 
The pH of the fluids within most cells in the human body must generally be kept between 6.5 and 7.5.
Controlling pH is important for maintaining homeostasis.
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19. 2-2
A molecule in which the charges are unevenly distributed is called a
polar molecule.
cohesive molecule.
hydrogen molecule.
covalent molecule.
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20. 2-2 A dissolved substance is called a solvent. solution. solute.
Suspension.
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21. 2-2
A compound that produces hydroxide ions in solution is called a(an)
base.
buffer.
acid.
salt.
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22. 2-2 Hydrogen bonds between water molecules result from
adhesion between water molecules.
magnetic attractions between water molecules.
uneven electron distribution in each water molecule.
ionic bonds in the water molecule.
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23. 2-2 On a pH scale, a value of 2 means that the solution has
equal concentrations of H+ and OH- ions.
the same concentration of H+ ions as pure water.
higher concentration of H+ than in pure water.
lower concentration of H+ than in pure water.
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