1. Formation of a new substance: This is the most fundamental characteristic of a chemical change. The original substances are transformed into entirely different ones with different properties.
2. Change in color: A change in color often signals a new substance has formed. For example, rusting iron turns reddish-brown.
3. Evolution of gas: Bubbles forming or a gas being released is a strong indicator of a chemical reaction. Think of baking soda reacting with vinegar, producing carbon dioxide gas.
4. Production of heat or light: Exothermic reactions release heat (like burning wood), while some reactions produce light (like fireflies).
5. Formation of a precipitate: This is when a solid forms from a solution, often as a result of a chemical reaction. For example, mixing solutions of lead nitrate and potassium iodide produces a yellow precipitate of lead iodide.
Important Note: While these are common signs of a chemical change, sometimes changes in color, temperature, etc. can be physical changes as well. To be sure, you should consider all aspects of the change.
