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Important Terms & Notes. Feb. 27-28, 2014. Energy Flow During Phase Changes of Matter. Energy must be ABSORBED by matter when the phase changes from: Solid to Liquid and Liquid to Vapor. Energy must be RELEASED by matter when the phase changes from:
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Important Terms & Notes Feb. 27-28, 2014
Energy Flow During Phase Changes of Matter • Energy must be ABSORBED by matter when the phase changes from: • Solid to Liquid and Liquid to Vapor. • Energy must be RELEASED by matter when the phase changes from: • Vapor to Liquid and Liquid to Solid.
Heat of Vaporization • The amount of heat required to change the phase of 1 gram of a substance in liquid form into 1 gram of vapor. Q = mL • For H20: L = 540 cal/g
Heat of Fusion • The amount of heat given up to change the phase of 1 gram of a substance in liquid form into 1 gram of solid form (crystal/ice). Q = mL • For H20: L = 80 cal/g
Questions Regarding the Phase Diagram • 1. The phase of water present along "Leg A" of the diagram is: • ? vapor • ? solid • ?Liquid • 2. The phase change taking place, in the right-to-left direction, along Leg "B" is: • ? melting • ? boiling • ? freezing
Questions Regarding the Phase Diagram • 3. According to the diagram, during a phase change the temperature: • ? increases • ? remains constant • ? Fluctuates • ? decreases • 4. At normal atmospheric pressure, water boils at: • ? 100 ºC • ? 0 ºC • ? -20 ºC • ? 120 ºC
Questions Regarding the Phase Diagram • 5. The phase of water present along "Leg E" of the diagram is: • ? solid • ? vapor • ? liquid • 6. According to the diagram, freezing requires • ? absorption of energy • ? no energy change • ? removal of energy
Energy Interchange in a Refrigerator’s Cooling Cycle • Heat is taken in from the inner compartment as the Refrigerant (liquid) evaporates in the pipes (Evaporator) and changes phase to vapor. • The vapor is compressed and then pumped through a heat exchanger pipe assembly (Condenser) where heat is given up to the outside environment allowing the vapor to condense into liquid.