Bubbles, Color, and Heat Are Clues a Reaction Happened

Hey there, scientist! I'm Atlas, and today we're going on a clue hunt. When substances mix and make something brand new, we call that a chemical reaction. But how do you know one happened? You look for clues! Clue 1 — Bubbling gas: When you mix baking soda and vinegar, tiny bubbles shoot up. That gas is carbon dioxide — a brand-new substance that was not in the cup before. Bubbles that keep forming (not just from stirring) are a strong reaction clue. Clue 2 — Color change: Sometimes mixing two liquids suddenly changes their color. Try mixing purple cabbage juice with baking soda and watch it turn green — that color shift tells you new substances formed inside the liquid. That is exactly what you will explore in the activity below! Clue 3 — Heat or cold: Touch the outside of a hand warmer and it feels warm. That warmth comes from a chemical reaction releasing energy. Some reactions go the other way and get cold — mix citric acid and baking soda in water and the container cools down. If temperature changes without a stove or ice, a reaction is probably happening. Clue 4 — New smell: Baking bread smells amazing because heat causes chemical reactions that make new scent molecules. A smell that was not there before is another reaction clue. Important note: ONE clue is not always enough. Scientists look for several clues together. And remember — not every change is a chemical reaction. Tearing paper, melting ice, or crushing a can are physical changes. The paper, water, and aluminum are still the same substances, just different shapes. In a chemical reaction, the starting substances are gone and something new is there instead. Ready to hunt for clues?