Heat and State Change

Overview

Students explore how adding and removing heat changes solids, especially focusing on melting and freezing. They use particle models to connect what they see (temperature and state) with what they can’t see (particle motion and arrangement), then conduct a short, repeatable investigation and compare findings.

Learning intentions

• Students will explain observable changes in solids when heat is added or removed using particle motion and arrangement models.
• Students will plan and conduct a safe investigation to test how heat affects melting and freezing.
• Students will record measurement data with reasonable precision and use it as evidence to support conclusions.
• Students will use appropriate science terminology to describe state changes (melt, freeze, temperature, solid).

Success criteria

• I can describe how heating and cooling affect a solid and name the change (melting/freezing).
• I can use a particle model to explain why the change happens (particles move closer together or further apart; motion changes).
• I can measure, record, and compare results from a fair test.
• I can identify possible sources of error and explain how they might affect the results.

Curriculum links

• Explains observable properties of solids, liquids and gases by modelling the motion and arrangement of particles.
• Plans and conducts repeatable investigations, including choosing variables and controlling a fair test; follows safe-use expectations.
• Compares methods and findings, recognises possible sources of error, and uses evidence to draw reasoned conclusions.
• Uses equipment to observe, measure and record data with reasonable precision.
• Poses investigable questions, makes reasoned predictions, and tests relationships.

Lesson structure (80 minutes)

1. 0–8 min · Launch and link. Teacher shows two quick scenarios: an ice cube left on a bench and an ice cube cooled in a freezer; students do a quick think about what changes and what stays the same. Students share ideas using sentence starters: “When heat is added…, the solid…because…”

2. 8–18 min · Direct teach: particle model for heat. Teacher models with roles (or mini-cards): particles in a solid are close and vibrate; when heated, particles move more and can separate enough for melting; when cooled, motion reduces and particles lock into position for freezing. Students complete a labelled particle sketch for melting and freezing, linking “heat → faster motion” and “cooling → slower motion”.

3. 18–28 min · Investigable question and prediction. On the board, teacher frames an investigable question: “How does water temperature affect how quickly an ice cube melts?” Teacher prompts variables: changed (initial water temperature), measured (time to fully melt), controlled (ice cube size/type, container size, start position). Students write a reasoned prediction and identify the controlled variables.

4. 28–35 min · Safety, method, and setup. Teacher demonstrates safe equipment handling and use of thermometer/timekeeping; class agrees on what counts as “fully melted” (no visible ice chunks). Students organise group roles: measurer, recorder, timer, equipment manager.

5. 35–58 min · Investigation (repeatable fair test). Groups test two conditions over timed trials (e.g., ice water vs room-temperature water). Teacher supports measurement accuracy and ensures consistent start timing (when ice contacts water). Students record data in a table: initial water temperature, start time, melt time, observations (appearance/temperature change).

6. 58–66 min · Quick share and compare. Teacher leads a gallery-style check: each group posts their average melt time and one observation about temperature change. Students compare findings with another group and discuss whether their results match the prediction.

7. 66–74 min · Freezing connection (remove heat). Teacher uses a short demo: placing a small amount of melted “water” back into a cooling condition (where available) or a prepared sample from earlier class. Students connect observations to the particle model (slower motion, particles lock into a solid). Students answer: “What changes when heat is removed, and how can we tell?”

8. 74–80 min · Exit ticket (evidence-based explanation). Students complete a short written response: describe melting or freezing, include particle reasoning, and identify one possible source of error. Teacher collects to gauge understanding before Lesson 6.

Resources

• Ice cubes (same brand/type/size), containers (identical for each group), measuring jugs/cups
• Thermometers (or temperature probes), timer/stopwatch
• Plastic trays/towels, heat-safe mats, protective eyewear
• Data tables (printable) with headings for temperature, time, observations
• Particle model cards or role-play props (optional), markers/whiteboard pens
• Sentence starters and science word bank on display (heat, temperature, solid, melt, freeze, particles)

Assessment

• Formative checks during particle model drawing: accuracy of “particles close/vibrate” and “motion changes with heat”.
• Observation during investigation: correct timing and consistent variable control.
• Exit ticket: evidence-based explanation using terminology and a plausible source of error (e.g., different ice size, delayed start timing, thermometer reading differences).

Differentiation

• Visual supports: a heat arrow diagram (heat added → melt; heat removed → freeze) and particle sketches on task sheets.
• Sentence starters: “I predict that… because…”, “My evidence shows…”, “One possible error was…”.
• Measurement scaffold: provide a partially completed data table and prompts reminding students to record in order (temperature first, then time).
• Support for EAL/SEN: offer a bilingual word bank where possible; allow drawing/labeling as part of explanations, not only writing.
• Extension for advanced learners (embedded, not separate): ask groups to calculate a simple difference between conditions and explain what the difference suggests about the relationship between temperature and melting rate.

Extension (optional)

• Create-a-presentation task is set for homework or the next lesson: “How temperature affects state changes.” Students include (1) particle explanation, (2) one piece of investigation evidence, and (3) a diagram of melting/freezing.