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Chemistry Review Balancing Equations In a chemical equation each side must have the same number and type of atoms. Examples: H2 + Na + O 2 H2O H2 NaH NEVER CHANGE THE CORRECT FORMULA IN ORDER TO BALANCE AN EQUATION! COEFFICIENTS ONLY! Challenge __C5H12 + __O2 __H2O + __CO2 + Energy _____ C _____ _____ H _____ _____ O _____ Law of Conservation of Matter The law states that matter cannot be created or destroyed. In a chemical equation, each side of the equation must consist of the same number of molecules. C(s) + O2(g) CO2(g) This chemical equation is balanced since there is one carbon atom and two oxygen atoms on each side, thus proving the Law of Conservation of Matter. Renewable vs. Nonrenewable Renewable energy sources are resources that can be sustained Examples: Solar Energy, Wind Energy, Geothermal Energy, and Hydropower Non-renewable energy sources are resources that cannot be sustained Examples: Gasoline, Coal, Natural Gas, and Diesel Physical and Chemical Changes Physical properties are observed with our senses and can be determined with out destroying the object Example: Color, shape, mass, length and odor Chemical properties indicate how a substance reacts with something else. Example: Iron rusting, wood burning and copper oxidizing Physical and Chemical Changes Physical Change: Identity stays the same Chemical Change: Identity changes Examples Sodium hydroxide dissolves in water ____________ Evaporation ___________ Milk sours ___________ Wood rotting __________ A tire is inflated with air __________ More Examples… Evaporation: _________ Melting: ___________ Wood- rotting: _________ Freezing: ___________ Metals, Non Metals, Metalloids (semi-metals) Properties of Each Metals: • • • • Conduct Malleable Reacts with acid Shiny Non-Metals: • • • • Do not conduct Brittle Do not react with acids Dull/not shiny Metalloids: • Conduct •Malleable •Do not react with acids •Dull/not shiny Conservation of Energy Exothermic Reaction- A reaction in which energy is given off or released and bonds form. As a result, new compounds are formed Endothermic Reaction- A reaction that requires the addition of energy. As a result, bonds break. Chemical potential 4H + 2O energy II 2 H2 + O2 2 H2O III I Time If the overall chemical potential energy decreases then the reaction is exothermic. If the overall chemical potential energy increases then the reaction is endothermic. Therefore this is an _________________ reaction. Types of Energy Kinetic Energy- The energy an object possesses due to its motion. Potential Energy- Stored energy. There are many different forms of energy such as: Heat Light Chemical Sound Energy Examples A rolling ball _______________ A photovoltaic cell ______________ A rollercoaster at its peak _____________ Steve jogging ______________ A parked car _______________ Heat of Combustion Heat of Combustion: The quantity of thermal energy given off when a certain amount of a substance burns. Heat of Combustion: Thermal energy released Mass of substance burned Thermal energy= M × C × ΔT Thermal energy= Mass of water × Specific heat of water × Change in temperature of water Example How much energy (kilojoules) is released by completely burning 25.0 mol hexane, C6H14? Solution: 25.0 mol hexane × 4141 kJ 1 mol hexane = 104,000 kJ - Burning 25 mol hexane would thus release 104,000 kJ of Thermal Energy Specific Heat of Water 4.2 J/g0C 1 Cal/ goC Specific Heat Capacity: quantity of thermal energy needed to raise the temperature of 1 gram of a material by 1oC. The End (: