Objective
Students will be able to identify the three states of matter (solid, liquid, gas), describe the properties of each state, and classify everyday objects by their state of matter. Students will explain how matter can change from one state to another through heating and cooling.
Standards
- NGSS 2-PS1-1 — Plan and conduct an investigation to describe and classify different kinds of materials by their observable properties.
- NGSS 2-PS1-4 — Construct an argument with evidence that some changes caused by heating or cooling can be reversed and some cannot.
Materials
- Ice cubes (1 per student group)
- Plastic cups and warm water
- Balloons
- Ziplock bags
- Objects for sorting: rock, pencil, water bottle, juice box, inflated balloon, rubber ball, milk carton
- States of matter sorting mat (3 columns: solid, liquid, gas)
- "What Is the World Made Of?" by Kathleen Weidner Zoehfeld
- Observation worksheet
- Chart paper and markers
Warm-Up (5 minutes)
Hold up three items: a rock, a cup of water, and an inflated balloon. Ask: "What is different about these three things?" Guide students to notice that the rock keeps its shape, the water takes the shape of its container, and the balloon is filled with something invisible. Introduce the word "matter" — anything that takes up space and has weight. Explain that matter comes in three forms called "states," and today we are going to explore all three.
Direct Instruction (12 minutes)
Read key pages from "What Is the World Made Of?" to introduce solids, liquids, and gases. After reading, build a class anchor chart with three columns:
Solids: Have a definite shape and size. They do not change shape when you move them to a different container. The tiny particles inside are packed tightly and vibrate in place. Examples: desk, book, rock, ice cube.
Liquids: Take the shape of their container but have a definite volume (amount). The particles can slide past each other. Pour water from a cup into a bowl to demonstrate. Examples: water, juice, milk, honey.
Gases: Have no definite shape or volume. They spread out to fill whatever space they are in. The particles move quickly in all directions. Blow up a balloon to show — the air inside is a gas that fills the balloon. Let a little air out to show it escaping. Examples: air, steam, helium.
Then demonstrate a state change: place an ice cube (solid) on a plate under the document camera. Ask students to predict what will happen. Explain that when we add heat, solids can become liquids (melting), and liquids can become gases (evaporation). When we remove heat, gases become liquids (condensation), and liquids become solids (freezing). Draw a simple diagram showing the cycle: solid — melting — liquid — evaporation — gas, and the reverse.
Guided Practice (10 minutes)
Distribute sorting mats and the collection of objects to each table group (4 students). Students work together to sort the objects into three categories: solid, liquid, gas. After sorting, each group shares one object and explains why they placed it in that column. Discuss tricky ones — is honey a solid or liquid? (It is a liquid because it takes the shape of its container, even though it is thick.) Is the air inside the juice box a gas? (Yes, even though we cannot see it.)
Then conduct a quick experiment: give each group an ice cube in a plastic cup. Set the cup in a sunny spot or on a warm surface. Students observe and record changes on their observation worksheet every 2 minutes (draw what they see and describe the state). Over 10 minutes, the ice melts. Ask: "What state did it start as? What state is it becoming? What caused the change?"
Independent Practice (10 minutes)
Students complete a states of matter worksheet with three sections:
- Sort 12 items into solid, liquid, or gas columns (word and picture bank provided).
- Draw and label an example of each state of matter from their everyday life (not from the lesson examples).
- Answer: "What happens to an ice cream cone on a hot day? What states of matter are involved? Explain using the words solid, liquid, and melting."
Assessment
- Formative: Listen to group discussions during the sorting activity. Can students justify their sorting choices using properties (shape, volume, particle movement)?
- Summative: Collect worksheets. Check the sorting accuracy (10 of 12 correct = proficient), everyday examples (must be correctly categorized), and the written explanation (must mention solid to liquid and use the word "melting").
Differentiation
- Struggling learners: Reduce sorting items to 6 instead of 12. Provide a reference card with definitions and pictures of each state. Use only familiar, obvious examples (rock = solid, water = liquid, air = gas) before introducing trickier ones.
- ELL students: Pre-teach vocabulary (solid, liquid, gas, melt, freeze, evaporate) with picture flashcards and gestures (fists clenched = solid, hands flowing = liquid, hands spreading wide = gas). Provide a bilingual glossary. Allow drawing-based responses on the worksheet.
- Advanced learners: Introduce plasma as a fourth state of matter (found in stars and lightning). Ask them to research and explain how evaporation and condensation are part of the water cycle. Challenge them to design an experiment that shows condensation (e.g., cold glass of water on a warm day).
- Students with IEPs: Provide the sorting activity with pre-cut pictures that students glue into columns instead of writing. Offer a simplified worksheet with sentence frames. Allow use of manipulatives throughout. Pair with a buddy for the observation experiment.
Closure (5 minutes)
Gather students and check on the ice cube experiment. Most ice cubes should be partially or fully melted. Ask: "What happened? What caused this change?" (Heat from the room melted the solid ice into liquid water.) Then play "State Showdown" — call out an object and students strike a pose: stand stiff with arms at sides for solid, wave arms fluidly for liquid, or spread out and wiggle for gas. Do 5 rounds. Close by asking: "Can you think of something at home that changes states?" (Ice in the freezer, steam from a pot, frost on a window.)