5. Physical vs. Chemical Changes

Matter can change in two very different ways, and telling them apart is a favorite GED® topic.

• A physical change changes the form of matter but not what it is. Melting ice, cutting paper, bending a wire, and dissolving sugar in water are physical changes — you still have the same substance, and they're usually easy to reverse.
• A chemical change forms a new substance with new properties. Burning wood, rusting iron, baking a cake, and digesting food are chemical changes.

Signs of a chemical change include a color change, gas or bubbles forming, light or heat being given off, an odor, or a solid (precipitate) appearing — and it's usually hard to reverse.

⚠️ Common misconception: dissolving sugar is a physical change — the sugar is still sugar, just spread through the water. Burning sugar is a chemical change, because new substances form.

💡 Tip: ask 'did a NEW substance form?' If yes → chemical; if it's the same substance in a new form → physical.