Matter and Heat / Irreversible Changes

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SWBAT support their claim with evidence that some materials are irreversibly changed when heat is added or removed.

Big Idea

To change or not to change scientists argue whether or not matter has changed it's properties when heat was added or removed.

NGSS Connections and Class Preparation

30 minutes

This lesson introduces the concept that when heat is added and removed from some materials, the change to the matter is irreversible.

NGSS Standards

2-PS1-4 Construct an argument with evidence that some changes caused by heating or cooling can be reversed and some cannot. 

Students identify properties of noodles and make observations after heat is added and removed. Afterwards students claim whether the changes were irreversible and support their claim with evidence.

Science Practices

- Analyzing and Interpreting Data (SP 4)

Students identify key properties and take observations of a material as it heated and cooled.

- Constructing Explanations (SP 6)

Students describe how the material's properties changed when heat was removed and added and decide if it was a irreversible change.

- Engaging in Argument from Evidence (SP 7)

Students review their observations to determine if after heat was added and removed from a material if the process was irreversible. Then support their answer with their data. 

Cross-cutting Concepts - Appendix G

- Cause and Effect (XC 2)

 Students observe how adding or removing heat can cause a material's properties to change.

Lesson Preparation

Purchase a bag of noodles.

Check that students have page 4 of the 'Heat Transfer' booklet. Or print lab page 4 attached to this lesson.

Lesson 1: Heat Transfer (cover and p. 1)

Lesson 2: Reversible Changes (p.2 and 3)

Lesson 3: Irreversible Changes ( p. 4)

Identify a heat source you can use, I am using a burner.

Pour water into a pan

Take lemonade cups out of the freezer


Colander to drain off water

Bucket to pour hot water into

The bucket will be next to the burner so that I do not need walk with the hot water.


extension cord

oven mitt


Question for the Day

10 minutes

Science starts with a question written on the board. This provides an opportunity for students to consider today's topic before the lesson has officially begun. 

This established routine helps keep transition time short and effective and redirects students' attention back to content while allowing time for focused peer interaction.

Question for the Day: When a material can change back and forth between phases, this is called a reversible change. What are materials that can change back and forth between phases when heat is removed or added?

Students discuss their ideas with their neighbors, then turn to face me to indicate they have finished.

I call on a volunteer to start a list of reversible materials.

"How would a scientist prove that these materials' properties stayed the same after heating and cooling? Yes, test the material!"

"Yesterday, we started a test on a liquid, to see what would happen to the liquid when we removed heat from it. What machine do we use to remove heat from an object? Right a freezer."

"I have removed your lemonade cups from the freezer so that you can identify the lemonade's phase and write it in your lab booklet on page 3. 

"After you write the lemonade phase, place your cup on your desk table and turn to page 4 in your  lab booklet .

"After the lemonade has melted you you will complete your lemonade lab."


Noodle Observations

30 minutes

I have started to heat a pan of water for the noodles.

I hand each student an uncooked noodle and direct them to write the properties that make the noodle a noodle in their lab booklet on page 4.

Volunteers share their noodle property words, which I write on the board. 

I collect the noodle pieces so that they do not end up on the floor and continue the discussion.

"Yesterday we learned some materials can move back and forth between solid and liquids. Do you think all materials are reversible? Please turn to your neighbor and explain your answer."

I listen to conversations to hear what examples students use to support their answer. Their discussions help me assess how well they have internalized the process of stating a claim and backing it with observations and/or experiences.

"I heard some fantastic explanations, you know what a scientist would do? Yes! Test some materials."

"Now that you have written the properties for the noodle, I will add some heat to the noodles. Then you can make some observations. Last, after the noodle has cooled to the same temperature as the noodle you held, I will pass them out so you can write your last observations and explanation."

"Please return to your desk, then I will place the noodles in the boiling water."

I have set the burner and pan under the document camera, so students can see what is happening in the pan.

I place the noodles in the pan. I connect to the previous lab, "When I added heat to the crayons they began to melt and turn into a liquid." Does it look like the noodles are melting? Are they turning into a liquid?"

After the noodles are cooked, I hold up a noodle and ask, "Heat was added to the material, what phase is it now, liquid, solid or gas?" I ask students how  they know, helping to scaffold their answer to include the definition of a solid. 

I direct students to write the phase of the noodle after heat was added. I use this moment to pour the hot water into a bucket that is by my desk.

This way I do not need to walk by the students with a pan of hot water.

"While the noodles are cooling to room temperature, let's take some observations on another material.

Burning Match Demo and Lab Observations

15 minutes

For the match demonstration, I fill out a table like the one in the students' lab booklets on the smartboard.

I hold up a match and ask the students to describe its properties. Before I light the match, I explain that I will be adding heat to the match when I rub it against the match box paper.

I invite students to rub their hands together and notice how their hands get warmer. Then I light the match and blow it out.

"Did the match change its phase when I added the heat? How about when I blew the flame out? If I let the match cool down some more will it have the same properties that it did before I lit the match?"

"Since the match cannot be changed back to it original state when we remove the heat, we say this is an irreversible change."

"I will pass out the noodles now so that you can complete your lab and explain if adding and removing heat to a noodle is a reversible or irreversible change and why."

When you finish your lab write up for the noodle, check that your lemonade has melted and then complete lemonade observations next.

Students started their lemonade investigation in the previous lesson.


10 minutes

I inform the kiddos that they may drink their lemonade after they complete their observations and answered all questions in their lab booklet.

When most students have finished their lemonade, students bring their lab book and meet me on the rug. I use a comparison chart to help students summarize the last 2 labs on reversible and irreversible changes.

With students input, we developed symbols to represent reversible and irreversible changes.

This promotes students to take ownership of their learning and addresses my visual and interpersonal learners.

I use this opportunity to informally assess if students can state that:

- some matters can be reversed, while others cannot

- reversible changes usually occur when the material changes phases

- heat can be added and removed from all materials

Before students are dismissed, I collect their lab booklets. I check the booklets for completeness and if the claim is supported with evidence.