Physical and Chemical Changes

Physical and Chemical Changes

  • Submitted By: Rubberducky
  • Date Submitted: 12/07/2008 9:08 PM
  • Category: Science
  • Words: 382
  • Page: 2
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Dallas & Davis Physical and Chemical Changes Lab Background Information: Phase Change: When a substance or compound changes from one of the states(liquid, gas, solid) but stays the same in chemical composition. Ex. Freezing liquid H20 to a solid state Temperature Change: When a substance or compound undergoes a change in heat, which is caused by, a reaction or external source of heat or cold. Ex. Boiling water increasing the waters temperature. Physical Change: When a compound or substance undergoes a change in physical structure or appearance, but the same chemical composition remains. Ex. Melting Solid ice into liquid water Chemical Change: When a substance or compound undergoes a direct change in its chemical composition. Ex. C + O2 C02 Nuclear Change: A change of energy and mass, one million times the size of a chemical change. Ex. The nuclear fission of uranium. Exothermic: When a reaction occurs that releases energy or heat as a cause of the reaction. Ex. Any Combustion reaction Endothermic: When a reaction occurs that absorbs or takes in energy or heat as a cause of the reaction Ex. Spraying Nitrogen dioxide into regular air. Analysis Physical Change See attached See attached See attached The energy or heat is being absorbed by the water to go towards the next phase change. SolidLiquidGas 95-100 degrees Celsius. Heat was being added from an external force. Nothing was added to the water except from energy. If you were to take the liquid or gas H20 and freeze it again, it would be in the same solid state and chemical composition as it was previously. Endothermic. Heat energy was being absorbed by the H20. Ultimately making the H20’s temperature change and phases change. Chemical Change Since they are on exact opposite ends of the ph scale, equal amounts of each chemical must be added to have an accurate double replacement reaction. The heat came from the double...

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