Melting and Freezing

Overview

In this lesson (lesson 3 of 8), students observe ice melting and link what they see to how particles move and are arranged in solids. They then model freezing using diagrams and discuss how this explains observable changes in matter.

Learning intentions

• WALT explain melting and freezing using a particle motion and arrangement model.
• WALT link observable properties (shape, form, temperature changes) to particle behaviour in solids and liquids.
• WALT use diagrams and scientific language to describe changes in states of matter.
• WALT participate in a brief investigation using safe, repeatable steps and record observations.

Success criteria

• I can describe what happens to ice as it melts (observable changes).
• I can model melting by saying particles in a solid move more and spread out as the substance becomes a liquid.
• I can explain freezing using the reverse idea: particles slow down and move closer together to form a solid again.
• I can use a diagram to show particle arrangement and motion for solid and liquid during a change.

Curriculum links

• Science — explain observable properties of solids, liquids and gases by modelling the motion and arrangement of particles.
• Science — plan and conduct repeatable investigations to answer questions, including safe use of equipment.
• Science — use appropriate representations (diagrams/models) to organise and describe patterns and relationships.
• Science — compare findings and reflect on possible sources of error, then draw reasoned conclusions.

Lesson structure (80 minutes)

1. 0–10 min · Hook & connect. Teacher shows a clear sequence (or live example) of ice in a container and asks: “What changed, and what stayed the same?” Students do a quick think-pair-share and record 1 observable change in their science notebook.

2. 10–25 min · Mini direct teach: particles model. Teacher introduces a simple particle diagram convention (solid: particles tightly packed, vibrating; liquid: particles closer but able to slide, moving more). Students annotate a provided model sheet: “Solid = packed; Liquid = spread/sliding.”

3. 25–45 min · Hands-on observation: melting investigation. Teacher sets up each group with an ice piece, a marked cup/beaker, a tray, and a thermometer if available; reminds students how to record safely and repeatable steps. Students follow a short method: measure initial temperature if possible, observe changes every 2–3 minutes for 15–20 minutes, record time/notes (“ice edge becomes wet”, “pool forms”, “temperature changes”).

• Teacher prompts: “What does your diagram need to show about particle motion during this change?”

4. 45–58 min · Group discussion: explain melting. Teacher provides sentence starters on the board: “When ice melts, the particles… so the substance…”. Students in groups create a “Cause → Particle model → Effect” explanation using their observations.

5. 58–68 min · Freezing as a concept (reverse model). Teacher demonstrates/uses a quick scenario (or shows a prepared photo sequence) of water turning back to ice, then asks students to predict particle changes. Students complete a “Melting vs Freezing” particle diagram comparing direction of motion and arrangement. They must include arrows and brief labels.

6. 68–78 min · Share & reasoned conclusion. Teacher selects 2–3 groups to share one observation and one diagram explanation; class checks whether explanations match evidence. Students do a short whole-class “Is this evidence or data?” check: they point to what they observed and what they inferred.

7. 78–80 min · Exit ticket. Students answer: “Explain melting in 3 steps using particles and observations. Then add one sentence about freezing.”

Resources

• Ice cubes or small ice blocks (pre-frozen) for 6–7 groups
• Clear cups/beakers with marker lines and trays to catch water
• Thermometers (if available) and/or timed observation sheets without temperature
• Safety: paper towels, bench protection, and a “hands dry” reminder
• Science notebooks or lesson recording sheets
• Printed particle diagram cards (solid and liquid) and a blank template for students
• Coloured markers/pens for arrows (movement) and labels (arrangement)

Assessment

• Teacher circulates during the investigation to check students’ observational recording (accurate, specific, and timed).
• Teacher listens for correct particle reasoning during group discussion (solid particles tightly packed vs liquid more able to move/slide).
• Exit ticket: evaluate whether students link observable melting to a particle motion/arrangement model and apply the reverse idea to freezing.

Differentiation

• Support: Provide a partially completed “Cause → Particles → Effect” frame, plus sentence starters and a word bank (solid, liquid, particles, move, closer, spread, melt, freeze).
• Support for struggling writers: Allow students to use icons/labels and add brief notes instead of full paragraphs in the investigation section.
• Extension for capable learners: Challenge students to include temperature in their explanation (e.g., “as it melts, the substance becomes warmer/changes state”), and to refine diagrams with more precise wording (vibrate vs slide).
• EAL/SEN: Use consistent diagram conventions, repeated teacher modelling, and pair roles (Recorder, Diagrammer, Reporter) so language demands are shared.

Extension (optional)

• For advanced learners: Add a second claim-evidence-reasoning prompt: “Which is a stronger explanation for melting in your group: temperature change or the formation of water? Explain using your particle model.”