Answer:
1.Formation of Gas
2.Color Change
3.
Formation of a precipitate
4.Energy Change
Step-by-step explanation:
Here are four signs that a chemical change has occurred:
1. Formation of a gas: If a gas is formed during a reaction, it indicates a chemical change. For example, if you mix baking soda and vinegar, carbon dioxide gas is produced.
2. Color change: If the color of the substances changes, it is often a sign that a chemical change has occurred. For example, when iron rusts, it changes from a silver color to a reddish-brown color.
3. Formation of a precipitate: A precipitate is a solid that forms from a solution during a chemical reaction. If a precipitate forms, it indicates that a chemical change has occurred. For example, when you mix silver nitrate and sodium chloride, silver chloride precipitates out of the solution.
4. Energy change: If energy is absorbed or released during a reaction, it is a sign that a chemical change has occurred. For example, when you burn a piece of paper, it releases energy in the form of heat and light.