Forming New Substances Cp. 2-11 Chemical ReactionsA 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).

2 Signs of a Chemical Reaction

14323 A Change of PropertiesSigns 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?Physical4DEMO

http://www.youtube.com/watch?v=nqDHwd9rG0s5 Bonds: Holding Molecules togetherA chemical bond is a force that holds 2 atoms together in a molecule.For a chemical reaction to take place, bonds must break.

6 Breaking and making bondsMolecules 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.

7 Student activity

8 New bonds, new substancesReaction of Chlorine with HydrogenA 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. Cl2H2plus2HClReaction of Chlorine with MetalsChlorine combines directly with all metals forming metal chloride salts. Cl2http://www.youtube.com/watch?v=VBReOjo3ri8NaplusNa+Cl-9://www.youtube.com/watch?v=VVxWucoVn9A&NR=1Gummy bear10