Answer:
Q1: Bubbles (gas formation)
Dissolving ( if solute is an ionic compound)
Color change
Q2: Fire burning
Salt dissolving
Q3: Bubbles (gas formation)
Color change
Dissolving ( if solute is an ionic compound)
Explanation:
Bubbles (gas formation)
Gas formation is mostly taken as an indicator for a chemical reaction, mostly in acid base reactions. Because when acid and base reacts water and carbon dioxide produces.
Dissolving of salt
Dissolving of salt in water is an example of a chemical change. Because when we put salt (NaCl) in water it changes into its ions (Na⁺ Cl⁻) by losing or gaining electrons. These Ions have totally different properties from the parent salt. So it is a chemical change.
Color change
Mostly we take color change as an indicator of a chemical change but it is not necessary. For example when we add two colors in a beaker its changes into a 3rd color without any chemical reaction.
Fire burning
Fire burning is an example of a chemical change. For example during wood burning, a chemical reaction takes place which changes the into ash and CO₂. the reactants and products have totally different properties.
