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Liquids and Solids

Liquids and Solids. Phase Changes. Solid to Liquid Melting Fusing Ice melts at 0 degrees Celsius. Phase Changes. Liquid to gas vapor ization E vapor ation Boiling A vapor is the gas phase of a substance that is liquid at room temperature water boils at 100 degrees Celsius.

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Liquids and Solids

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  1. Liquids and Solids

  2. Phase Changes Solid to Liquid • Melting • Fusing • Ice melts at 0 degrees Celsius

  3. Phase Changes Liquid to gas • vaporization • Evaporation • Boiling • A vapor is the gas phase of a substance that is liquid at room temperature • water boils at 100 degrees Celsius

  4. Phase Changes Gas to Liquid • Condensation • Water vapor condenses to water liquid at 100 degrees Celsius

  5. Phase Changes Liquid to Solid • solidification • freezing • Crystallization • water freezes at 0 degrees Celsius

  6. Phase Changes Solid to Gas (skip liquid) • sublimation • Dry ice (Solid carbon dioxide) sublimes into carbon dioxide gas at room temperature

  7. Phase Changes Gas to Solid (skip liquid) • deposition • Water vapor deposits into ice crystals on cold surfaces

  8. Heating Curve

  9. Heating Curve of Water

  10. Cooling Curve

  11. Cooling Curve gas condensing liquid freezing solid

  12. During a phase change: The temperature does not change (flat line) Average kinetic energydoes not change Potential Energy changes!

  13. KE increases PE increases

  14. Energy equations Q = mcΔt Can only be used when there is no phase change occurring

  15. Energy equations Q = mhf Can only be used when there is melting or freezing occurring Hf is the heat of fusion (Notice there is no temperature term, since temp does not change)

  16. Energy equations Q = mhv Can only be used when there is boiling or condensing occurring Hv is the heat of vaporization (Notice there is no temperature term, since temp does not change)

  17. Example # 1 • Which equation would you use for this problem? • How many joules of heat are absorbed when 50 g of water is heated from 30.2 degrees C to 58.6 degrees C? • Q = mcΔt

  18. Answer Q = 50g x 4.18 J/goc x (58.6 – 30.2oC) Q = 5936J

  19. Example # 2 • Which equation would you use for this problem? • How many joules of heat are required to melt 225 g of ice at 0 degrees C? • Q = mHf

  20. Answer Q = 225g x 334 J/g Q = 75,150 J Q = 75.15 kJ

  21. Example # 3 • Which equation would you use for this problem? • How many joules of heat are required to vaporize 423 g of water at 100 degrees C? • Q = mHv

  22. Answer Q = 423g x 2260 J/g Q = 955,980 J Q = 955.98 kJ

  23. Why does boiling 1 g of water require so much more energy than melting 1 g of water? Boiling = 2260 J/g Melting = 334 J/g

  24. Lots of energy needed to separate the particles from liquid to gas

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