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Phase Changes

Phase Changes. Courtesy www.lab-initio.com. constant. Temperature remains __________ during a phase change. Water phase changes. Kinetic Energy, Potential Energy and a Heating Curve.

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Phase Changes

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  1. Phase Changes Courtesy www.lab-initio.com

  2. constant Temperature remains __________ during a phase change. Water phase changes

  3. Kinetic Energy, Potential Energy and a Heating Curve. • Since Temperature is a measure of "Average Kinetic Energy", any change in temperature is a change in Kinetic Energy. • Since temperature does not change during a phase change, the energy that is gained or lost is Potential Energy. • Remember the 3 Ps. Plateau, Phase change and Potential Energy Change.

  4. Add these abbreviations to graph! KE PE PE = Potential energy KE = Kinetic energy KE PE KE

  5. Exothermic Processes Processes in which energy is released as it proceeds, and surroundings become warmer Reactants  Products + energy

  6. Endothermic Processes Processes in which energy is absorbed as it proceeds, and surroundings become colder Reactants + energy  Products

  7. Standard Temperature • Standard Temperature equals: • 273 Kelvin (273 K) • 0 C

  8. Converting Celsius to Kelvin Many problems involving temperature require that the temperature be in KELVINS! Kelvins = C + 273 °C = Kelvins - 273

  9. Melting point • Melting - change from solid to liquid • Melting point - SPECIFIC temperature when melting occurs. • Each pure substance has a SPECIFIC melting point. • M.P. of Water = 0°C (32°F)

  10. Boiling Point • Boiling Point – temperature at which a liquid boils • Each pure substance has a SPECIFIC boiling point. • Examples: • B.P. of Water = 100°C (212°F)

  11. What’s the temperature at point B in kelvins?

  12. What’s the temperature at point C in kelvins?

  13. Which region is kinetic energy the highest? IV III II I

  14. Which region has the lowest potential energy? IV III II I

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