Unit Plan 5 (Grade 5 Science): Heating & Cooling Matter

Focus: Measure and graph changes in the weight of matter when substances are heated, cooled, or mixed, and use the data as evidence that the total weight of matter is conserved.

Grade Level: 5

Subject Area: Science (Physical Science • Matter & Conservation)

Total Unit Duration: 5 sessions (one week), 50–60 minutes per session

I. Introduction

In this unit, students investigate what happens to the weight of matter when substances are heated, cooled, or mixed. Using digital scales and simple setups (melting ice in a sealed container, dissolving salt, warming/cooling water), they collect measurement data, represent it with graphs, and look for patterns. Students confront common ideas like “the weight disappears” when ice melts or water evaporates and instead build the understanding that, in a closed system, the total weight stays the same, even when matter changes state or appearance.

Essential Questions

• What happens to the weight of matter when we heat, cool, or mix substances?
• How can measurements and graphs help us decide if weight is conserved during changes?
• Why does matter sometimes seem to “disappear” (like melting or evaporating), even though the total weight is the same in a closed system?
• How do scientists and engineers depend on conservation of matter when they design processes and products?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Describe what is meant by conservation of matter (the total amount/weight of matter stays the same in a closed system).
2. Use scales to measure the weight of substances before and after heating, cooling, or mixing (e.g., ice → liquid water, room-temperature water → warm water, salt + water solution).
3. Create tables and graphs (bar or line graphs) of their measurement data, showing before vs. after weights.
4. Interpret their graphs to decide whether the total weight changed or stayed the same, and propose reasons for any small differences (e.g., measurement error).
5. Use their data as evidence to explain that, for these changes, the total weight of matter is conserved even when matter’s state or appearance changes.

Standards Alignment — 5th Grade (NGSS-Aligned)

• 5-PS1-2 — Measure and graph quantities to provide evidence that regardless of the type of change that occurs when heating, cooling, or mixing substances, the total weight of matter is conserved.
  • Example: Students measure and graph the total weight of a sealed container with ice before and after melting; they use the data to argue that the mass did not change, even though the appearance and state did.

Success Criteria — Student Language

• I can measure and record the weight of substances before and after heating, cooling, or mixing.
• I can make a graph that compares before and after weights for each change.
• I can use my graphs to explain whether the total weight changed or stayed about the same.
• I can explain that when we heat, cool, or mix substances in a closed system, the total weight of matter is conserved.
• I can recognize that small differences in my measurements might be due to measurement error, not matter disappearing.