# Physical Science December 7, 2011 Ms Cilli Pages 206-209.

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Physical Science December 7, 2011 Ms Cilli Pages 206-209

Describe the energy changes that take place during chemical reactions. Classify chemical reactions as exothermic or endothermic. Explain how energy is conserved during chemical reactions.

C 3 H 8 + 5O 2  3CO 2 + 4H 2 O

Chemical Energy: Chemical reactions involve the ________ of bonds in the reactants and the ________ of bonds in the products.

Breaking bondsForming Bonds

Is heat lost or gained? 1. A plastic bottle of water is placed in a freezer. After several hours, the water has frozen solid. 2. A chef places a stick of solid butter in a saucepan, and heats the saucepan over low heat on a stove. After several minutes, the stick of butter has melted.

Exothermic: Endothermic:

1. A plastic bottle of water is placed in a freezer. After several hours, the water has frozen solid. 2. A chef places a stick of solid butter in a saucepan, and heats the saucepan over low heat on a stove. After several minutes, the stick of butter has melted. 1. A plastic bottle of water is placed in a freezer. After several hours, the water has frozen solid. 2. A chef places a stick of solid butter in a saucepan, and heats the saucepan over low heat on a stove. After several minutes, the stick of butter has melted.

Heat is on the _____ side

All together now

Is it endothermic or exothermic? (Look and ask yourself what side the heat is on) C 3 H 8 + 5O 2  3CO 2 + 4H 2 O + 2220kJ 2HgO + 181.7 kJ  2Hg + O 2 Is it endothermic or exothermic? (Look and ask yourself what side the heat is on) C 3 H 8 + 5O 2  3CO 2 + 4H 2 O + 2220kJ 2HgO + 181.7 kJ  2Hg + O 2

Which one is not one of the 5 types of chemical reactions? a.synthesis b.decomposition c.single-replacement d.double-replacement e.All of these are chemical reactions Which one is not one of the 5 types of chemical reactions? a.synthesis b.decomposition c.single-replacement d.double-replacement e.All of these are chemical reactions

Independent Practice: – Read section 7.3 – Work on the study guide Homework: – Complete the section 7.3 HW – Due Thursday, December 8 by 8PM