Here's why:
* Chemical reactions involve the formation of new substances with different chemical properties. This means the atoms within the molecules rearrange to form different molecules.
* Changes in state of matter (solid, liquid, gas) are physical changes. The chemical composition of the substance remains the same, only the arrangement of the molecules changes.
Examples of observations that DO indicate a chemical reaction:
* Change in color: A new substance forms with a different color.
* Production of gas: Bubbles forming indicate the release of a gas.
* Formation of a precipitate: A solid forms from a solution.
* Change in temperature: Energy is released or absorbed during the chemical reaction.
* Production of light: A reaction produces light, such as in a fire or a glow stick.
Remember: While a change in state of matter does not indicate a chemical reaction, it can sometimes accompany one. For example, ice melting is a physical change, but if the ice is melting due to a chemical reaction like the burning of wood, then a chemical change has also occurred.
