Unit Plan 5 (Grade 2 Science): Changing Matter with Temperature

Focus: Observe changes when materials are heated or cooled and use evidence to argue which changes can be reversed and which cannot.

Grade Level: 2

Subject Area: Science (Physical Science • Science & Engineering Practices)

Total Unit Duration: 5 sessions (one week), 30–45 minutes per session

I. Introduction

In this unit, students explore what happens when everyday materials are heated or cooled. Through simple, safe demonstrations and observations, they notice when a material changes state or form (melting, freezing, softening, hardening) and when it changes in a way that cannot go back, like cooking an egg or toasting bread. Students learn to use evidence from what they see to decide whether a change is reversible (can go back to how it was) or not reversible (cannot easily go back), and they practice constructing arguments to explain their thinking in line with 2-PS1-4.

Essential Questions

• What happens to materials when we heat or cool them?
• How can we tell if a change caused by heating or cooling can be reversed or cannot be reversed?
• What evidence can we use from our observations to support our ideas about these changes?
• Why is it important to know which changes are reversible when we cook, build, or make things in real life?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Describe what happens when common materials are heated (e.g., melt, soften, cook, darken) and cooled (e.g., freeze, harden, firm up).
2. Observe and record before-and-after properties of materials that have been heated or cooled (color, texture, hardness, shape).
3. Sort examples of changes into “can be reversed” (e.g., melted butter that can harden again) and “cannot be reversed” (e.g., cooked egg, burnt toast).
4. Use simple data tables, drawings, and notes to keep track of changes they see in demonstrations or photos.
5. Construct an argument with evidence that some changes caused by heating or cooling can be reversed and some cannot, using “because” to connect ideas to observations (2-PS1-4).
6. Share their reasoning with peers and respond to questions or different ideas respectfully.

Standards Alignment — 2nd Grade (NGSS-Aligned)

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

Success Criteria — Student Language

• I can tell what happened to a material when it was heated or cooled.
• I can decide if a change can be reversed (go back) or cannot be reversed and explain why.
• I can use my observations (what I saw, felt, or noticed) as evidence in my argument.
• I can say or write an argument like: “I think this change is not reversible because ___.”
• I can listen to a partner’s idea and compare it to my own, using evidence to agree or disagree politely.