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2.  Draw a water molecule. Label the elements and the charges.

4.  What is the chemical formula for water? H2OH2O  Two hydrogen atoms and one oxygen atom

5.  Why is water considered a polar molecule?  Because parts of the molecule have either a positive (+) or negative (-) charge  The oxygen and hydrogen are bonded because they share electrons, but they do not share them equally. So, the oxygen becomes slightly negative and the hydrogen is slightly positive.

6.  What is a hydrogen bond?  An attraction between the hydrogen of one water molecule and the oxygen of a separate water molecule.  Hydrogen bonds are like a magnetic attraction- they do not involve shared electrons

7.  Which has stronger hydrogen bonds- water or alcohol? How do you know?  Water has stronger hydrogen bonds  More drops of water fit on a penny, because they are better able to “hold on” to each other  Water needs to be at a higher temperature to boil because the hydrogen bonds are preventing the water molecules from increased movement

8.  What is cohesion?  Cohesion is the attraction between two molecules that are the same (water to water)  Water is very cohesive because it has strong hydrogen bonds

9.  What is heat capacity?  The ability to absorb heat energy without drastic changes in temperature.

10.  What has a higher heat capacity- water or alcohol?  Water has a higher heat capacity.  Alcohol boiled at a much lower temperature, meaning it’s hydrogen bonds weren’t as strong

11.  What is a solvent? Solute? Solution?  Solution: mixture of water and dissolved substances  Solute: the material that is being dissolved  Solvent: the liquid that the solute is being dissolved into  Solution: Salt water  Solvent: Water  Solute: Salt

12.  What affect do dissolved solutes have on freezing temperature?  Dissolved solutes lower the freezing temperature of liquids  This is why salt water must be cooled to a much lower temperature in order to freeze that plain water

13.  What is unique about water when it freezes?  It expands, causing ice to float  Water is the only liquid that does this

14.  Why is the layer of ice on top of lakes important?  It provides insulation for the water below

15.  What is the pH of pure water? 77

16.  What is the pH of an acid?  0-6.9  In other words, less than 7

17.  What is the pH of a base?  7.1-14  In other words, greater than 7

18.  Name three acidic foods  Lemon juice, coffee, sour candy  Acidic foods taste tart or sour

19.  Name three items that are bases  Bleach, ammonia, cleaner

20.  How do you find the average of a set of numbers?  Add everything up, and divide the sum by the number of numbers  Average of 6, 10, and 5  6 + 10 + 5 = 21  21 / 3 = 7

21.  What is the freezing point of pure water?  0 °C

22.  What is the boiling point of pure water?  100 °C

23.  What is a covalent bond?  A covalent bond connects two atoms by sharing an electron  The hydrogen is bonded to the oxygen (in the same molecule) through a covalent bond

24.  Why is polarity important to life on earth?  Since water is polar, water can dissolve lots of substances  This is why water is called the universal solvent.

25.  Why is cohesion important to life on earth?  Cohesion is responsible for surface tension, which allows certain organisms to float.

26.  Why is adhesion important to life on earth?  Adhesion helps move water upwards through the stems of plants, since they don’t have any other way of moving the water against the force of gravity.

27.  How is water’s heat capacity important to life on earth?  The water in our cells can absorb a lot of heat energy without killing our cells  Oceans can absorb a lot of heat energy from the sun without getting so hot that it kills all of the fish and other organisms.

28.  Water Notes  Do Nows, PQQ’s and TOD’s  2.2 Worksheet  Complete a cheat sheet  Continue to redo the practice test! Practice makes perfect