<em>John Dalton considered atom as the smallest particle but later on this theory failed due to discovery of electron,proton and neutron. This three are the subatomic atomic particle. Later on Murray Gell-Mann discovered the quarks which forms the neutrons and protons and determine overall charge on them. </em>
<u>Conclusion</u> - Electron,proton and neutron are subatomic particles not smallest particles.
those are all physical changes and most physical changes can be undone like crushing a pice of metal you can flatten it back out you anwser is physical change
