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Forming New Substances Cp. 2-1. Chemical Reactions. A chemical reaction is a process in which one or more substances change to make one or more new substances. The properties are different from the original substance(s).
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Chemical Reactions • A chemical reaction is a process in which one or more substances change to make one or more new substances. • The properties are different from the original substance(s).
Signs of a Chemical Reaction 1 2 4 3
A Change of Properties • Signs of chemical changes are not always accurate. Is this a chemical change? A gas is formed! No-this is a change of state, which you recall from 7th grade is what type of change? Physical
DEMO http://www.youtube.com/watch?v=nqDHwd9rG0s
Bonds: Holding Molecules together • A chemical bond is a force that holds 2 atoms together in a molecule. • For a chemical reaction to take place, bonds must break.
Breaking and making bonds • Molecules are always bumping into each other. • If enough energy is present, this will break existing bonds. • The atoms are free to rearrange and form new substances.
New bonds, new substances Reaction of Chlorine with Hydrogen A mixture of Chlorine and Hydrogen explodes when exposed to sunlight to give Hydrogen Chloride. In the dark, no reaction occurs, so activation of the reaction by light energy is required. Cl2 H2 2HCl plus Reaction of Chlorine with Metals Chlorine combines directly with all metals forming metal chloride salts. Na Cl2 Na+Cl- plus http://www.youtube.com/watch?v=VBReOjo3ri8
://www.youtube.com/watch?v=VVxWucoVn9A&NR=1 Gummy bear