When conducting an experiment two types of reaction can occur, Chemical reactions or Physical changes.
You can easily tell between them as physical changes reversable and chemical reactions aren’t.
Other ways of telling if a chemical reaction happened is colour change (beware some physical changes change colour then turn back), smells, effevessing & flames.
You also have chemical reactions in cooking for example: boiling an egg and cooking toast are chemical reactions as they are irreversible yet warming custard and freezing yogurt are physical changes for you can change them back to their original form.
Thanks for looking at this weeks STEM Post!!!