How do I know if a chemical reaction has occurred?!?

The video tutorial explains chemical reactions, highlighting that they occur when substances change their chemical structure. It distinguishes between physical and chemical changes, using water as an example. The tutorial outlines five indicators of chemical reactions: formation of precipitate, gas, water, color change, and temperature change. Each indicator is explained in detail, emphasizing how they help identify chemical reactions.

How can the formation of gas indicate a chemical reaction?

Describe what a temperature change during a chemical reaction indicates.