General ---------Biology ------------------Online-------------       -wilcox@sunline.net Ch.  2 :  The Chemical Context of Life

The following asks questions followed by blanks.  You can answer the question mentally or you can print this page and fill in the blank by hand.  If you have questions, or are unsure of your answers, ask a question at the start of class.  Do not turn this page in.  Only turn in those assignments that specifically direct you to turn them in.  The Assignments for each chapter can be viewed by clicking on the Assignments link at the bottom of the contents page of each chapter, e.g.  Ch. 2 Contents..

Lets start with something you probably already know about elements and molecules based on the hierarchy table from the previous chapter. Describe the relationship between:
atoms and molecules: _____________________________________________

There are a bunch of elements, some of the names will be familiar.  Click here to see a chart of all the elements, and use your "Back" button to return.

Now use simple reasoning to answer some questions that will help sort out the meaning
of the terms: atom, element and molecule. 

When you drink a glass of H₂O, what substance are you drinking?  _________

Water (H₂O) contains how many atoms of the element hydrogen (H)?  ____
Water contains how many atoms of the element oxygen (O)?____
How many atoms make up one molecule of H₂O? ____
How many atoms make up two molecules of water (2H₂O)? ____
How many different elements are in a molecule of water? ____

An atom of H or O cannot be broken down into subatomic particles (protons, neutrons, 
electrons) by chemical reactions or by the sort of high temperatures and pressures
normally possible on earth.  Only a "nuclear reaction" can split an atom.

To illustrate another aspect of elements, assume you had a bar of pure gold, i.e. the matter in the bar is made up entirely of atoms of the element gold. You could divide the bar into smaller and smaller pieces, and the smallest piece, that would have the characteristics of gold, would be a single atom.  Split the atom and you have protons, neutrons and electrons, and they are the same in any element: gold, lead, hydrogen, calcium, etc.  All protons are essentially identical. Ditto for neutrons and electrons. Combine the protons, neutrons and electrons in one way and the properties of calcium emerge.  Combine more protons, neutrons and electrons, and the properties of gold emerge, as in "emergent properties."

By varying the the number of protons, neutrons and electrons combined together, you could theoretically produce all the elements known to science. 

Only hydrogen and later helium were present in the first hundred million years after the universe came into existence.  It took billions of years for stars to condense from clouds of hydrogen gas and then burn, grow old and die.  When a star dies it causes a spectacular explosions called a "super nova."  A star dies because it runs out of hydrogen fuel, can no longer burn, then collapses in on it self causing very extreme pressures that  fuse the protons, neutrons and electrons making all the other elements, such as the carbon, hydrogen and oxygen that make up most of our bodies.  One reason you are so special is that you are made out of "star dust."

Optional activities:

Go to google.com and search for 

Summary:  You should be able to:

• recognize the definitions of elements, atoms and molecules
• answer simple questions using the terms "atoms, molecules and elements" (see fill-in-the-blank questions above)
• explain to a child why they are made out of "star dust "