Unit 2 — Changes to Matter
Description
This unit develops students' understanding that the total weight of matter is conserved when it changes form, even when physical or chemical changes occur. In the first part of the unit, students investigate whether mixing two or more substances creates a new substance. They measure the properties of original substances, mix them, and then measure the properties of the resulting mixture or new substance to determine whether a chemical change occurred. They recognize patterns in their observations that reveal cause-and-effect relationships. In the second part of the unit, students measure and graph the weight of matter before and after physical changes such as heating, cooling, melting, freezing, dissolving, and mixing. By collecting and analyzing multiple datasets, they gather evidence that regardless of the type of change, the total weight of matter is always conserved.
Essential Questions
- How can we determine whether mixing substances creates a new substance?
- If a frozen water bottle melts, does its weight change?
Learning Objectives
- Conduct an investigation collaboratively to produce data on whether mixing two or more substances results in a new substance
- Identify cause-and-effect relationships to explain changes when substances are mixed
- Measure and graph quantities such as weight before and after physical and chemical changes
- Provide evidence that the total weight of matter is conserved when substances are heated, cooled, mixed, or undergo other changes
- Understand that science assumes consistent patterns in natural systems
Supplemental Resources
- Highlighters for marking observations in data tables for data organization
- Index cards for recording initial and final properties of substances for tracking changes
- Chart paper for creating graphs and tables of weight data for data visualization
- Markers for labeling mixtures and new substances for investigation documentation
- Pencils for recording detailed observations and measurements for data collection
Crosscutting Concepts
Disciplinary Core Ideas
Science and Engineering Practices
Students use informational texts and digital sources to conduct research, gather evidence, and build knowledge across all science units. They quote accurately from texts, draw inferences, summarize and paraphrase information in science notebooks, write opinion pieces supporting claims with evidence, and incorporate multimedia components into presentations. Reading informational texts and writing research-based explanations are explicitly aligned to science performance expectations throughout all six units.
Students apply mathematical reasoning and computational thinking across all units. They measure and graph physical quantities such as weight, volume, and temperature; use coordinate plane graphing to represent scientific data; convert measurement units within standard systems; and reason abstractly and quantitatively when analyzing data as evidence for scientific explanations. Mathematical practices including modeling with mathematics and using appropriate tools strategically are integrated throughout investigation and data analysis activities.
Formative Assessments
- Students conduct investigations with controlled variables and fair tests, measuring properties before and after mixing substances
- Students record and compare observations of mixtures and new substances formed from mixing
- Students create graphs and tables to organize weight data from heating, cooling, dissolving, and mixing experiments
- Students use data as evidence to explain whether matter was conserved during physical or chemical changes
Summative Assessment
Students demonstrate understanding of physical and chemical changes through a unit test that assesses their knowledge of properties and conservation of matter.
Benchmark Assessment
— not configured —
Alternative Assessment
Students may demonstrate understanding through a hands-on investigation with teacher guidance, using simplified data recording sheets or sketches to document properties before and after mixing substances. Sentence frames, word banks, and visual property comparison charts may be provided to support written or oral explanations of whether a chemical or physical change occurred.
IEP (Individualized Education Program)
Students may benefit from graphic organizers that help them record observations before and after changes to matter, reducing the cognitive load of open-ended note-taking during investigations. Providing a structured data table with labeled columns for properties such as weight, color, and texture can support accurate measurement and recording. Where written output is a barrier, allow students to describe their observations and conclusions orally or through labeled diagrams. Chunking the investigation process into numbered steps with visual cues will help students follow multi-stage procedures independently.
Section 504
Students should be given extended time to complete measurement tasks and record data during hands-on investigations, as precision work with tools such as scales can require additional processing time. Preferential seating near the demonstration area ensures clear visibility during teacher modeling of physical and chemical changes. Printed copies of any directions or procedural steps displayed on the board should be provided so students can reference them throughout the investigation without losing their place.
ELL / MLL
Providing a visual word bank with illustrated definitions for key vocabulary — such as physical change, chemical change, dissolve, conserve, and weight — will support students in connecting scientific language to the concepts they observe. Teachers should use visual demonstrations and physical materials when introducing changes to matter, pairing actions with clear, simple language to build comprehension before students begin independent investigations. Allowing students to discuss observations with a bilingual partner or record initial thinking in their home language before translating to English can help bridge understanding during data collection and analysis.
At Risk (RTI)
Connecting this unit to familiar, everyday examples of matter changing — such as ice melting in a drink or sugar dissolving in water — can help build the background knowledge students need before engaging with more abstract conservation concepts. Providing partially completed data tables or sentence frames for recording observations lowers the entry barrier while still requiring students to engage meaningfully with the science content. Teachers should check in frequently during investigation phases to confirm students are measuring and recording accurately, offering immediate corrective feedback before misconceptions take hold.
Gifted & Talented
Students who demonstrate early mastery of conservation of matter can be invited to investigate scenarios that complicate simple cause-and-effect explanations, such as exploring whether apparent weight loss during heating is a true violation of conservation or evidence of a gas being released. Encouraging students to design their own controlled investigations around an unanswered question about physical or chemical changes deepens scientific thinking beyond what the standard curriculum requires. Teachers might also challenge these students to connect conservation of matter to broader scientific principles, prompting them to consider why consistent patterns in natural systems are foundational to all of science.