1. Phase Changes

2. Drill Convert 15 degrees Fahrenheit to Celsius Convert your answer to Kelvin How many states of matter exist? What are they?

3. Review: 3 Phases of Matter Solid Liquid Gas But are there only 3?

4. STATES OF MATTER Four States vs. Four Phases? Solid Liquid Gas PlasmaIs there another state?

5. What is a Phase Change?Phase Change Is a change from one state of matter (solid, liquid, gas ) to another. Phase changes are physical changes because: - It only affects physical appearance, not chemical make-up. - Reversible

6. What happens during a phase change? During a phase change, heat energy is either absorbed or released. Heat energy is released as molecules slow down and move closer together. Heat energy is absorbed as molecules speed up and expand.

7. Types of Phase Changes

8. Melting Phase change from a solid to a liquid Molecules speed up, move farther apart, and absorb heat energy

9. Freezing Phase Change from a liquid to a solid Molecule slow down, move closer together and release heat energy.

10. PHASE CHANGES Description of Phase Change Term for Phase Change Heat Movement During Phase Change Solid to liquid Melting Heat goes into the solid as it melts. Liquid to solid Freezing Heat leaves the liquid as it freezes.

11. PHASE CHANGES Description of Phase Change Term for Phase Change Heat Movement During Phase Change Liquid to gas Vaporization, which includes boiling and evaporation Heat goes into the liquid as it vaporizes. Gas to liquidCondensation Heat leaves the gas as it condenses. Solid to gasSublimation Heat goes into the solid as it sublimates.

12. Phases of Matter Is ENERGY being ADDED or TAKEN AWAY in this phase change: © 2013 S. Coates SolidLiquid ADDED The added energy has caused the chocolate particles to speed up. Before they were vibrating in place, now they are moving fast enough to slip past one another. ADDED The added energy has caused the chocolate particles to speed up. Before they were vibrating in place, now they are moving fast enough to slip past one another.

13. Phases of Matter Is ENERGY being ADDED or TAKEN AWAY in this phase change: © 2013 S. Coates LiquidGas ADDED The added energy has caused the water particles to speed up. Before they were moving fast enough to slip past one another, now they have enough energy to break away from one another and expand.

14. Phases of Matter Is ENERGY being ADDED or TAKEN AWAY in this phase change: © 2013 S. Coates LiquidSolid Taken Away Taking away energy from a puddle slows the water molecules down so that they no longer slide past one another.

15. STATES OF MATTER SOLID LIQUID GAS PLASMA Tightly packed, in a regular pattern Vibrate, but do not move from place to place Close together with no regular arrangement. Vibrate, move about, and slide past each other Well separated with no regular arrangement. Vibrate and move freely at high speeds Has no definite volume or shape and is composed of electrical charged particles

16. Vaporization (Boiling) Phase change from a liquid to gas. It occurs at the boiling point of matter. Molecules speed up, move farther apart, and absorb heat energy.

17. Evaporation Phase change from a liquid to a gas on the surface of a liquid (occurs at all temperatures). Molecules speed up, move farther apart, and absorb heat energy.

18. Condensation Phase change from a gas to a liquid. Molecule slow down, move closer together and release heat energy.

19. Sublimation Phase change from a solid to a gas. Molecules speed up, move farther apart, and absorb heat energy.

20. Deposition Phase change from a gas to a solid. Molecules slow down, move closer together and release heat energy.

21. Graphing a Phase Change

22. Melting & Boiling Points Melting Point: The temperature at which a solid changes into a liquid. Boiling Point: The temperature at which a liquid changes into a gas. What is a Freezing point? Compare the freezing and melting points of water.

23. Summary

24. What is the melting point of this substance? 50˚C 100˚C The boiling point? Just to review before we start…

25. It takes energy to heat stuff up! for pure substance in single phase - can calculate how much E needed using: Q = mC  T Q = energy in Joules m = mass in grams C = specific heat capacity  T = change in temperature = T f - T i on other hand, when something cools down, energy is released!

26. Temperature Time Q = mC liquid  T Q = mC solid  T Q = mC gas  T C = specific heat capacity (amount heat required to raise temp of 1g of pure substance by 1  C) C is a physical constant unique for every pure substance CAN YOU FIND THE SPECIFIC HEAT OF WATER ON YOUR REFERENCE TABLE? IIIIII IV V

27. So, how do we calculate the amount of energy required during a phase change? H F = Heat of Fusion (Q = mH F ) H V = Heat of Vaporization (Q=mH V ) We use one of these two constants instead of specific heat and delta T Q = mC  T

28. How much heat is absorbed when 10 grams of ice melts at 0 o C? Heat absorbed = mass of substance x heat of fusion of substance Q = mH f = (10 g)(334 J/g) = 3340 J Where does this energy go? – Particles must overcome forces of attraction to move farther apart during phase change (s → l)

29. H 2 O changing from solid to liquid requires 3,340J/g It takes a lot more energy to go from liquid to gas than from solid to liquid. Why? H 2 O changing from liquid to gas requires 22,600J/g * greater energy required to change from liquid to gas because particles are spreading farther apart!

30. Heating curve of H 2 O

31. Graphing a Phase Change – Why is there no change in temperature during a phase change? – Define melting and boiling points. – What is the melting point and boiling point of water? – At what temperature does water freeze and become a solid?