To Do… Electronic homework (Lon-Capa) HW6 Type 1 due Monday, April 21 by 7 pm; HW6 Type 2 due Wednesday, April 23 by 7 pm Wednesday’s lab: Be prepared Read lab book PreLab Assignment Proper attire Watch videos 1

Big Ideas – Discussed All matter is made up of atoms. Atoms are in constant motion (kinetic molecular theory). Chemical reactions are re- arrangements of atoms (substances change into other substances). 2

Big Ideas – To Be Discussed Chemical changes are accompanied by energy changes. At the same conditions, some substances are liquids, some are solids, and others are gases. Atoms have structure. 3

Questions to Consider: Why are there molecules? Why are there phases of matter? Why does water, for example, have the properties that it does? 4

Overall goal: Atomic StructureChemical Bonding3D Molecular StructureMolecular Properties 5

Clicker Question Which is lower in potential energy? Which is more stable? H 2 /O 2 or H 2 O Lower PEMore Stable A) H 2 /O 2 H 2 O B) H 2 O H 2 /O 2 C) H 2 /O 2 H 2 /O 2 D) H 2 O H 2 O 6

Big Ideas – Energy A system is more stable with lower potential energy. Achieving low potential energy is a driving force. Thus, if energy is transferred into a system, the system will work to transfer this energy out. 7

Clicker Question Which is lower in potential energy and more stable? Lower PEMore Stable A) Unburned match Unburned Match B) Burned Match Unburned match C) Burned Match Burned Match D) Unburned match Burned Match 8

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Clicker Question A banana is frozen by liquid nitrogen. Label each process as endothermic or exothermic. (The system is underlined.) BananaLiquid Nitrogen A)EndothermicEndothermic B)ExothermicEndothermic C) EndothermicExothermic D) ExothermicExothermic 10

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Clicker Question Is the freezing of water an endothermic or exothermic process? (The system is underlined.) A)endothermic B)exothermic C) neither 13

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Exothermic: more energy leaves the system overall Endothermic: more energy goes into the system overall 2H 2 + O 2  2H 2 O2H 2 O  2H 2 + O 2 15