It was typically taught that physical changes are differentiated from chemical changes because they could be “undone” or that they had “no chemical reaction.” Which was very confusing, because you can’t uncut paper, and dissolving stuff in water clearly results in different chemicals being produced, yet both were examples of physical changes (actually the latter is sometimes taught as a chemical change). Furthermore, most chemical changes are actually reversible.
It has since been recognised that this classification is BS, and most changes actually exist on a continuum.
Physical Vs chemical changes.
It was typically taught that physical changes are differentiated from chemical changes because they could be “undone” or that they had “no chemical reaction.” Which was very confusing, because you can’t uncut paper, and dissolving stuff in water clearly results in different chemicals being produced, yet both were examples of physical changes (actually the latter is sometimes taught as a chemical change). Furthermore, most chemical changes are actually reversible.
It has since been recognised that this classification is BS, and most changes actually exist on a continuum.