Biology Ch. 2 Crossword (2)

2. An important class of catalysts in living things.
4. The number of protons in an atom.
5. The central core of an atom and consists of the protons and neutrons.
9. An atom or molecule with an electrical charge.
11. The result of the combination of two compounds.
12. Solutions in which water is the solvent.
14. A solution in which no more solute can dissolve.
16. The reactions in which electrons are transferred between atoms.
18. Pure substances that cannot be broken down chemically into simpler kinds of matter.
19. The OH- ion.
20. Chemical substances that neutralize small amounts of either an acid or base added to a solution.

1. The breaking apart of a molecule into two ions composed of opposite charge.
2. Reactions that involve a net absorption of free energy.
3. The rate at which atoms or molecules of any substance moves.
6. Most elements tend to undergo ________, combining in ways that cause their atoms to become stable.
7. The simplest part of a substance that retains all of the properties of the substance.
8. The amount of energy needed to start the reaction.
10. The quantity of matter an object has.
13. The energy in a system that is available for work.
14. A mixture in which one or more substances are uniformly distributed in another substance.
15. A solution is an ____ if the number of hydronium ions is greater than the number of hydroxide ions.
17. Forms when two atoms share one or more pairs of electrons.