1. Chapter 2-1

2.  A substance made up of two or more different types of atoms bonded together.  Elements are to compounds as letters are to words.  Elements change when they form compounds.  Sounds of letters change to form words

4.  All compounds have the same ratio of elements.  Ammonia: 3 hydrogen for every nitrogen  Ratio of 3:1  Hydrazoic acid: 1 hydrogen for 3 nitrogen atoms  Ratio of 1:3  Different ratios = different properties

5.  A chemical formula uses chemical symbols and the ratios of elements to represent a compound.  Carbon Dioxide: 1 carbon and 2 oxygen  Symbol for Carbon CC  Symbol for Oxygen  O  CO 2  Subscript: Number to the lower right, tells the number of atoms

7.  Hydrogen Chloride: 1 hydrogen and 1 chlorine  Water: 2 Hydrogen and 1 Oxygen  Ammonia: 1 Nitrogen and 3 Hydrogen  CH 4 C3H8C3H8

8.  Hydrogen Chloride: 1 hydrogen and 1 chlorine  HCl  Water: 2 Hydrogen and 1 Oxygen H2OH2O  Ammonia: 1 Nitrogen and 3 Hydrogen  NH 3  CH 4  Methane: 1 Carbon and 4 Hydrogen C3H8C3H8  Propane: 3 Carbon and 8 Hydrogen

9.  Page 45 numbers 1, 2, 4 and 6.