How Can We Change Matter? (2 Day Lesson)

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Objective

SWBAT: Explain and model the various ways that matter can change

Big Idea

Students learn how to determine, at the molecular level, if matter is changing chemically or physically.

Overview

This lesson develops students' understanding of physical and chemical changes so that they can better address MS-LS-2-3.

Students research physical and chemical changes and consider what happens to the matter at the particle level. They certainly don't need to know how the matter changes, especially chemically, they just need to know that different types of matter is created.

This lesson follows the lesson on using PHeT simulations to introduce the Law of Conservation of Matter. Students begin to make connections that if a chemical change is taking place then the matter on the reactant side will be different arrangements of the matter that the reaction started with on the reactants side.  

During a physical change, we don't have products and reactants, because a reaction is not taking place, meaning that the matter is still composed of the same molecular structures. Molecules then can either change state or shape, but composition remains the same. This still supports the Law of Conservation of Matter, because matter isn't being added or taken away, it's only changing physical form.

DO NOW

4 minutes

Since students are going to be working with various ways that matter can be changed, I ask them to think about and list all the ways that they have changed matter since they have been awake.

Students sometimes have difficulty getting started so I give them an example.  I usually use the example of something that is relevant and easy to understand, such as chewing food.  I am not trying to get them to determine what type of change, they just need to realize that chewing food changes it in some way.

I then give students a few minutes to write down their ideas.

Share Do Now Responses

2 minutes

Students then share their lists from the Do Now with their group.  They write down other students ideas that are not on their own lists.  Later the lists will be used to help students pick a topic to research.

Introduce Research Activity

5 minutes

Now that students have a list of ways that matter can be changed, it is time for students to research various examples to develop an understanding of different types of changes.

To establish clear expectations and understanding, I share Physical Chemical Changes Activity Overview and Rubric with students. I explain that each person in the group will pick a different example from their list. Students answer the four parts on the instruction sheet and share their responses on a Google document. The Google document is shared with everyone in the group and me.

As students begin researching, I circulate around the room answering any lingering questions that students may have and help students as they research online.

My main goals include encouraging:

1) Students to explain the difference between physical and chemical changes 

2) Explain what happens to molecules/atoms during each type of change, which helps model their understanding of each type of change.

Students must complete at least one example, but are encouraged to complete two changes in their group's document.

Students Research and Creating Document

40 minutes

As students research, I circulate around the room ready to ask several questions to help students develop an understanding of physical and chemical changes.  

Probing questions:

  • Are the properties of the matter, such as density, changing from this change?  

Rationale: I want my students to apply what they're learning to other phenomena (Crosscutting concepts), and this question asks them to do that.  

  • Is a chemical reaction taking place?  How do you know?  What does this mean in terms of reactants vs. products?  Molecules?

If students are struggling to make connections, it isn't going to do them any good to keep creating their project if they're doing it incorrectly. Use these interactions to formatively assess student work and address any misconceptions. Be sure to ask questions that lead to reflection, refinement and deeper understanding!

My students were struggling a little with this idea of matter being conserved, so I had them model their understanding by acting as molecules. This idea builds off of their experiences from Using Theatrics and Songwriting to Bring Molecular Molecules to Life on modeling air movement. I find that having students act as molecules helps build understanding, so I promote it in my classroom.  

Modeling Reactions