Distinguishing a chemical change from a physical change means looking beyond what is immediately visible. This Grade 7 science worksheet explores how atoms rearrange during chemical reactions, how matter is conserved, and how temperature measurements can provide evidence of energy transfer.

Students investigate a familiar reaction involving baking soda and citric acid dissolved in water. The mixture fizzes as carbon dioxide gas forms, and its temperature often decreases as energy moves from the surroundings into the mixture. By examining these observations together, students practise explaining why scientific conclusions need multiple pieces of evidence rather than relying on bubbles alone.

From observations to particle models

The reading passage connects observable changes with processes at the particle level. Students distinguish chemical reactions, which form different substances through atomic rearrangement, from physical changes such as boiling water, where liquid water becomes water vapour without becoming a different substance.

The resource also develops understanding of conservation of matter. In a closed system, atoms are rearranged rather than created or destroyed. Students consider how particle models can represent this idea, why temperature changes matter when investigating reactions, and how measurement errors may affect the evidence collected.

What students practise

• Multiple-choice questions about atomic rearrangement, carbon dioxide formation, temperature measurement and the difference between physical and chemical changes.
• True-or-false statements that address common misconceptions, including the idea that bubbles always prove a chemical reaction has occurred.
• Short-answer explanations requiring students to describe reaction observations, explain why boiling is a physical change, and use particle models to show rearrangement of atoms.
• A labelled diagram, categorizing activity and short note to extend students' work with chemical change, evidence and scientific explanations.

Worksheet, answer key and teacher support

• Printable student worksheet with a topic-focused reading passage and varied response activities.
• Separate PDF answer key for checking responses.
• Student Notes lines at the bottom of the worksheet for recording key information.
• Teacher Guide included in the answer key PDF, with Learning Objectives, Teaching Tips, Discussion Questions and Common Mistakes.

Ways to use this resource

Use this chemical and physical changes worksheet when introducing chemical reactions, reviewing particle models, or consolidating ideas after an investigation. The baking soda and citric acid example gives students a concrete context for connecting visible evidence with gas formation and energy transfer. The boiling-water comparison helps reveal whether they can explain the difference between a change of state and the formation of a new substance.

Written explanations give teachers a chance to check how students support claims with observations, while the answer key and teacher guidance make it easier to review responses and address misconceptions. Students practise a key scientific habit: collecting measurements, considering possible errors and using evidence to explain what happened rather than treating one observation as conclusive proof.