8th Grade Critical Skills

1. Water

     a) One molecule of water is made of 2                           hydrogen atoms and 1 oxygen atom

     b) Chemical symbol for oxygen- O

     c) Chemical symbol for hydrogen –H

 2. Compound- two or more chemical elements           chemically bound together

 3. Chemical formula- a description of how many       elements are in a compound

    b) The chemical formula for water is  H2O

    c)  For water, 1 g = 1 mL = 1 cm3 = 1 cc


4. Archimedes of Samos

     a) Considered to be one of the greatest                         scientists of ancient Greece

     b) Began the development of scientific                         notation

     c) Eureka! – The Story of the Crown of King                 Minos

     d) Discovered the Law of  Density


Density =  Mass (g) / Volume  (mL or cm3)


     e) Law of Volume of Rectangles (regularly-                 shaped objects)


Volume = Length  x  Width  x  Height

5. Directly inspired Galileo and Isaac Newton to        investigate the mathematics of motion

6. Specific gravity

     a) The ratio of the density of an object to the             density of a standard,  usually water

     b) Specific gravity is a numeric (it has no                     units)

7. ‘Mystery’ Knowledge That Few Take Notice Of

     a) “What you see on the macro-scale, you see             on the micro-scale’.” (Plato)

     b)  For example, let's compare the atom to our            solar system

           (1) There is  a lot of space between the Sun                  and the planets.  There is also a lot of                      space between the nucleus and the                          electrons  in an atom.

              (2) The planets travel in elliptical orbits                         around the Sun.  The electrons travel                        in elliptical orbits around the nucleus                      of the atom.

               (3) The planets spin (rotate) on their                               axes as they travel (revolve) around                         the Sun.  Likewise, the electrons spin                       (rotate) as they travel (revolve)                                   around the nucleus.                                                                           

Professor's Note:  You learned in class that  what we see on the macro-scale (i.e., the solar system), we will often see on the micro-scale (i.e., the atom).  If this observation is a universal principle, I suspect that both either both gravity and electromagnetism are found in both scales or gravity is simply a result of electromagnetism.  My thoughts are included here to demonstrate the way I am trying to teach you to think about the natural world around you.  -Mr. Mac

8. Just as there is a lot of space inside the atom,        there is a lot of space between molecules

9. Example: Salt dissolving in water

     a) The salt crystals break down into sodium               and chlorine ions

     b) The sodium and chlorine ions go into the                 empty spaces between the water molecules

     c) Ion- a charged atom that has lost or gained           one or more electrons.



10. Table Salt

     a) The chemical name of table salt is ‘sodium             chloride’

     b) The chemical formula of sodium chloride is           ‘NaCl’

     c) The chemical symbol for sodium is ‘Na’

     d) The chemical symbol for chlorine is ‘Cl’

     e) A molecule of sodium chloride contains one           sodium atom and one chlorine atom

     f) Salt water is an example of a solution

11. Salinity

     a) Salinity is defined as a description of how               much salt is dissolved in a given amount of           water

     b) The average salinity of fresh water is 0%

     c) The average salinity of water in the Atlantic          Ocean is 35%

     d) The average salinity of water in the Dead               Sea is 350%  (This water is considered                     saturated- all of the empty space between             the water molecules is filled up with                         dissolved salt)

Floating in a Swimming Pool & the Dead Sea

Note how much of the swimmer's body remains above water in the Dead Sea video clip.  The space between the water molecules in Dead Sea water is totally occupied.  This leaves no space for your body so you float higher and have trouble swimming in it.  The Dead Sea is about eight times saltier than the Atlantic Ocean.

12. The density of ocean water also limits the               amount of cargo a ship can carry.  

13. Specific Gravity

     a) This is the ratio of the density of an object             or substance to the density of a standard,               usually water.

     b) If the specific gravity is less than 1, that                 object will float.

     c) If the specific gravity is greater than 1, that           object will sink.

14. Conductivity

     a) This is a measure of how well something                 can conduct electricity

     b) Salt water is a better electrical conductor               than fresh water

     c) The human body has salt water in it and can           conduct electricity very well

     d) Most materials than can conduct electricity           can also conduct heat

15. When working on your Putt-Putt Boat,  it will        help if you know some boating terms.

     a) Bow- the front of the hull

     b) Stern- the back of the hull

     c) Hull- the body of the boat that sets in the               water

     d) Starboard- the right side of the boat

     e) Port- the left side of the boat

Salt Dissolving in Water

Chemical Reaction Between Sodium and Chlorine to Form Sodium Chloride (Table Salt)

Merchant Badge Notes