Physical vs Chemical Change

What is a Physical Change?

A physical change affects a substance’s form or state, not its chemical identity. The molecules stay the same, but their arrangement or movement changes.

• No new substance is created.
• A physical change affects only physical properties (like shape, size, state, or appearance).

Examples include:

• Melting (solid → liquid) and freezing (liquid → solid)
• Boiling and condensation
• Cutting, crushing, breaking, or dissolving

Often reversible using temperature or pressure.

What is a Chemical Change?

A chemical change happens when a substance’s structure changes, creating new matter. 

During a chemical change, atoms are rearranged, and chemical bonds are broken or formed. 

A new substance is created with different properties (color, texture, reactivity).

Signs of a chemical reaction:

• Gas production (bubbles, fizzing)
• Color change that can’t be reversed (like rust)
• Heat or light given off (temperature change)
• Formation of a solid (precipitate) from two liquids

Usually irreversible under normal conditions.

Fun Facts

Here are some interesting facts about physical and chemical changes:

• Chewing food is a physical change, but digesting it is a chemical change—your stomach acid breaks it down!
• Freezing water is a physical change, but water electrolysis splits it into hydrogen and oxygen gases—a chemical change!
• Bubbles in soda are physical (carbon dioxide gas escaping), but bubbles during baking come from a chemical reaction!
• When silver tarnishes, it’s reacting with sulfur in the air—a slow chemical change.

Review

Let’s quickly recap what we learned about physical vs chemical change:

• What type of change is melting butter? Physical
• What change happens when wood burns? Chemical
• Is dissolving sugar in water a physical or chemical change? Physical
• What change creates a new substance? Chemical