Life on Earth
Audesirk & Audesirk
Prentice-Hall, Inc.


Chapter 2: At a Glance


Matter and Energy
  • Energy exists in several forms that can be interconverted.

    The Structure of Matter
  • Atoms, the smallest units of elements, are composed of still smaller particles.
  • Atoms will react with other atoms only when there are vacancies in their outermost electron shells.

    Chemical Bonds: Joining Atoms to Make Molecules
  • Atoms can become stable by gaining or losing electrons, forming charged ions; the attraction between oppositely charged ions produces ionic bonds.
  • Atoms can become stable by sharing electrons with other atoms, forming covalent bonds.
  • Hydrogen bonds are weak electrical attractions between the polar parts molecules.

    Organic and Inorganic Molecules

    Water and Life
  • Water interacts with many other molecules.
  • The ph of a solution is a measure of its concentration of hydrogen ions.
  • A buffer helps maintain a solution at a relatively constant pH.
  • Water moderates the effects of temperature changes.
  • Water forms an unusual solid, ice.
  • Water molecules tend to stick together.



  • Designed in cooperation with Andrew Stull and Steven Brunasso.

    Last Update - July 25, 1997

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