3 What is a Phase Change? It 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
4 What happens during a phase change? During a phase change, heat energy is either absorbed or released.
5 What is Exothermic change? Heat energy is released as molecules slow down and move closer together.Example: Gas to Liquid
6 What is Endothermic change? Heat energy is absorbed as molecules speed up and expand.Example: From solid to liquid
8 What is Melting? Phase change from a solid to a liquid Molecules speed up, move farther apart, and absorb heat energy
9 What is Freezing? Phase Change from a liquid to a solid Molecules slow down, move closer together and release heat energy.
10 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.
11 What is Evaporation? Phase change from a liquid to a gas Molecules speed up, move farther apart, and absorb heat energy.
12 What is Condensation? Phase change from a gas to a liquid. Molecule slow down, move closer together and release heat energy.
13 Sublimation is? Phase change from a solid directly to a gas. Liquid state doesn’t happen..!!!Molecules speed up, move farther apart, and absorb heat energy.Example:As dry ice (frozen carbon dioxide gas)gets warmer, it turnsinto carbon dioxide gas
14 Deposition is? Phase change from a gas to a solid. Again.. Liquid state doesn’t happen..!!!Molecules slow down, move closer together and release heat energy.
15 Melting & Boiling Points What is Melting Point:The temperature at which a solid changes into a liquid.What is Boiling Point:The temperature at which a liquid changes into a gas.What is a Freezing point?Point at which liquid becomes solid.
17 Summary When Heat energy is released it is called? Exothermic change Think of the prefix Exo as Exit
18 Summary When Heat energy is absorbed it is called? Endothermic change The prefix endo means in
19 Graphing a Phase Change Why is there no change in temperaturewhen changing solid to liquid and liquid to gas?Because the heat energy is used get the moleculesto move faster and faster, until ice changes to liquidand eventually liquid will change to gas
20 Graphing a Phase Change Define melting point* Melting Point happens when all the moleculeshave so much energy that they now changeinto the liquid state of matter
21 Graphing a Phase Change What is the melting point and boiling point of water?Pure Water meltsat 0 C or 32 FPure Water boilsat 100 C or 212 FGraphing a Phase Changeoooo
22 Graphing a Phase Change At what temperature does water freeze and become a solid?Pure Water freezes at0 C or 32 Foo
23 DirectionsTake out your science notebook or your phone notes and write down thefollowing questions and answers
24 Assessment and Review… 1. Name six common phase changes.Melting, freezing, vaporization, condensation, sublimation, and deposition.2. What happens to the temperature of a substance during a phase change?The temperature of a substance does not change during a phase change.3. What is the difference between evaporation and boiling?Evaporation takes place at the surface of a liquid and occurs at temperatures below the boiling point. Boiling point of pure water is 100 degrees Celcius
25 4. How does the energy of a system change during a phase change? Energy is either released or absorbed during a phase change.5. What happens to the arrangement of water molecules as water melts and freezes?The arrangement of molecules becomes less orderly as water melts and more orderly as water freezes.
26 6. What is the difference between Endothermic and Exothermic change? During endothermic change energy is absorbedfrom the surroundings, such as hot stoveDuring exothermic change energy is releasedinto the surroundings7. What are the freezing and boiling points of pure waterFreezing point is 0 degree Celcius and 32 degreesFahrenheitBoiling point is 100 degrees Celsius and 212 degrees Fahrenheit
27 Homework tonight…… Complete: “Molecules on the move worksheet” Write the correct Phase of matter and also include whether it was an Exothermic or Endothermic changeHW is due tomorrow..!! Oh yes..!