Freezing

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Objective

SWBAT identify the phase change of freezing through video and comparative analysis.

Big Idea

By understanding the particle movement, students will be able to explain how a liquid can change into a solid through freezing.

Engage

5 minutes

Teacher Tip: This lesson requires an internet connection for the video demonstration, as well as a projector.  I use a SMARTBoard for this lesson, as well. The intention of this lesson is for students to understand that when you take away heat from something, it changes.  In this case, when you remove heat from water, it changes into a solid or ice.  This lesson addresses NGSS MS-PS1-1 as students are required to make connections between the amount of thermal energy and the behavior of the molecules. 

To begin the lesson, students are faced with a quick-write question to consider and answer independently on their student notes sheet

If we know adding heat to a solid will change it to liquid, what will taking away heat from a liquid do?

After 3-4 minutes, I will ask students to share their responses with the class. I am looking for someone to say, maybe it will change to solid or freeze. 

 Freezing

Explore

5 minutes

This next section is where you'll need the internet connection to show the ice bomb demonstration.  I prep the students for the demo by reading the questions below (found on notes sheet) aloud to the class. I also explain that dry ice is very, very cold and will instantly remove the heat from the water.  

Questions on notes sheet: 

Watch the ice bomb video and answer the questions below.

What happens to the water when it’s placed in dry ice?

What happens to the “bomb” casing once the water freezes?

I show the video to the class one time.  Students can respond to the questions during this time, if they so choose. I play the video a second time for them.  They respond to the questions for sure this time if they haven't already done so. After they are finished responding, I will ask a student to share his/her response with the class. 

Explain

5 minutes

This next section is an independent reflection on what freezing is molecularly at this point.  They have seen molecules in action with the melting lesson, and based on what they know about liquids and solids, they should be able to explain that the molecules are slowing down and moving closer together to eventually become a solid.

The question they will answer is found on the notes sheet and is as follows: 

Describe what’s happening to the molecules of water when heat is being taken away (freezing). 

Elaborate

15 minutes

Together, as a small group, students will work on completing the analysis chart comparing water and ice, this analyzing the process of freezing.  Students will choose one of the italicised options beneath each bolded section for either water or ice. I added the selection for students with learning difficulties who wouldn't necessarily be able to fontload the responses. After about 10 minutes, I will go over the chart, soliciting answers from students, on the SMARTBoard. 


Evaluate

5 minutes

Students will finally reflect independently on the process of freezing by explaining how molecules can go from liquid to solid.  They will use the prompt below to help them: 

Describe how the molecules on the left go from the molecules on the right. (Use words from the word bank to help you.)

molecule   add heat    take away heat   faster   slower