© Shannon W. Helzer. All Rights Reserved. Unit 10 Phases and Phase Changes

© Shannon W. Helzer. All Rights Reserved. Phases of Water What are the three primary phases of the substance we know as “water?” a.Solid, Liquid, and Gasoline b.Hard, Gel, and Fluid c.Solid, Liquid, and Vapor d.Vapor, Gas, Steam 10-1

© Shannon W. Helzer. All Rights Reserved.  However, once the water began to freeze, the temperature remained a constant.  Once all of the water had changed phases and turned to ice, the ice’s temperature then began to fall.  Key Point: During phase changes, there is no change in temperature.  What happens to the temperature as a mass (i.e. water) freezes?  Let us take a look by putting a beaker of water into the freezer. Freezing  At first, the temperature of the water dropped. 10-2

© Shannon W. Helzer. All Rights Reserved. What did we observe?  First, we see that the temperature of the ice remained constant until it all melted.  Next, the temperature of the water increased until it began to boil.  Once it began boiling, the temperature of the water remained constant until it boiled away.  Once the water was completely boiled away to steam, the temperature of the steam began to increase.  Key Point: During phase changes, there is no change in temperature. Melting  What happens to the temperature as a mass (i.e. ice/water) heats up?  Let us take a look. 10-3

© Shannon W. Helzer. All Rights Reserved.  In the two previous slides we observed that the temperature of a substance (i.e. water and ice) remained constant at certain times when energy was added or removed.  What were these times?  Freezing, melting, condensing, and boiling are all known as phase changes of matter.  During these processes, energy transferred to or from the water did not increase or decrease the temperature of the water.  Instead it provided or removed the energy needed to change the phase of water. Phase Changes 10-4

© Shannon W. Helzer. All Rights Reserved. Latent Heats  Latent heat changes the phase of a substance without changing its temperature.  Latent heat of fusion, L f, is the amount of heat required to melt 1 kg of ice into water. L f = 3.34 x 10 5 J/kg.  Latent heat of vaporization, L v, is the amount of heat required to turn 1 kg of water into steam. L v = 2.26 x 10 6 J/kg.  How much heat is required to turn 1.0 kg of steam back into water? Water into ice?  -L v = x 10 5 J/kg and -L f = x 10 6 J/kg.  The negative sign indicates that the substance must give up or lose heat in order to change into the new phase.  The heats required to change the phase of a substance are: 10-5

© Shannon W. Helzer. All Rights Reserved. Phase Change/Latent Heat Graph  A graph for the temperature v. time for water as it goes from ice to water to boiling and finally to a vapor is shown below.  The same graph also applies for the reverse. LfLf LvLv Melting BoilingCondensing Freezing Water Ice Vapor 10-6

© Shannon W. Helzer. All Rights Reserved. WS 47 #2  g of ice at – 10.0  C is placed on a hot plate. When the hot plate is turned off and completely cooled, there is still g of ice remaining in the water.  Place point “A” at the approximate starting point on the graph for H2O.  Place point “B” at the approximate ending point on the graph for H2O.  What is the final temperature of the ice and water mixture? Why?  How many different “heats” will you need to solve this problem? Why?  How much heat did the hotplate transfer to the ice? 10-7

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  Watch the phase change animation below. Which points on the graph indicate the possible initial phase and the possible final phase of the H 2 O? 10-8

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  Watch the phase change animation below. Which points on the graph indicate the possible initial phase and the possible final phase of the H 2 O? 10-9

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  Watch the phase change animation below. Which points on the graph indicate the possible initial phase and the possible final phase of the H 2 O?  This animation is like WS 47 #

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  Watch the phase change animation below. Which points on the graph indicate the possible initial phase and the possible final phase of the H 2 O?  See WS 47 #

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  Watch the phase change animation below. Which points on the graph indicate the possible initial phase and the possible final phase of the H 2 O? 10-12

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  Watch the phase change animation below. Which points on the graph indicate the possible initial phase and the possible final phase of the H 2 O? 10-13

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  Watch the phase change animation below. Which points on the graph indicate the possible initial phase and the possible final phase of the H 2 O?  See WS 49 #

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Phase Diagrams – Initial and Final Points  WA 4-13

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  WA 4-13

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  WA

© Shannon W. Helzer. All Rights Reserved.

Locking Nut Gauge Adjustment Nut Gauge Drip Cup Temperature Sensor Steam Generator Securing Nut

© Shannon W. Helzer. All Rights Reserved. Phase Diagrams – Initial and Final Points  WA