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Lesson 3-7: The Water Molecule and Changing State (Freezing and Melting)

Page history last edited by mariaelizabethbunn@... 5 years, 7 months ago



Engaging the Student (Entry Task) 

Developing the Ideas--Lesson

Checking for Understanding (exit ticket)

Student Handout 
Teacher/Lesson Notes

2 class periods

Part A:

  • See Engage Activity on Page 2 of Lesson 3-7 Part A (Note: You'll need to freeze water overnight.
  • Show this movie:  Ice Bomb 
  • Ask students the engagement discussion questions on page 2 of lesson plan. 


Part B: 

  • See Engage Activity on Page 2 of Lesson 3-7 Part B
  • Have students watch a small piece of ice melting.
  •  Show students this video:  Ice Melting on Different SurfacesIn this video, ice is placed on two similar-looking black surfaces—one aluminum and the other plastic. The ice melts faster on the aluminum because it is a better thermal conductor than the plastic.
  • Discuss student observations.
  • Ask students:
  1. Where do you think the energy came from to melt the ice? (The energy comes from the air and from the surface that the ice is placed on, both of which are at room temperature. Since room temperature is warmer than the temperature of the ice, energy is transferred from the surface and the air to the ice).
  2. What do you think happened to the speed of the molecules in the ice when it was heated? (The water molecules moved faster). 






Part A:

Part B: 



View the full lesson plan here:


Answer Key to Student Activity Sheet:


  1. Summary
    • Students will mix ice and salt in a metal can to make it very cold. They will then see liquid water and ice form on the outside of the can. Students will watch an animation of water molecules arranged as ice.
    • Students will see a small piece of ice melt on an aluminum surface. Students will explain the energy transfer and molecular motion which cause the change in state from a solid to a liquid.
    • Students will see and discuss an animation of ice melting and compare the state changes of water to the state changes of other substances.
    • Student will also investigate sublimation of dry ice through a teacher demonstration, or video if dry ice is not readily available. 


      2.  Objectives:

    • Students will be able to explain on the molecular level why a low enough temperature can cause the water vapor in air to condense to liquid water and then freeze to form ice.
    •  Students will be able to explain on the molecular level the process of heat transfer and molecular motion that causes a solid to melt to form a liquid.
    • Students will also be able to explain how the arrangement of water molecules is different from most other substances when it changes state from a solid to a liquid.





Part A:


Part B: 






Have groups use the water molecules and to model the freezing and melting of water.


See links corresponding water molecule model lessons in the "Checking for Understanding" column of the main wiki page for this Big Idea.




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