* New substances are formed: The reaction produces copper (Cu) and sulfur dioxide (SO2), which are entirely different substances from the original copper sulfide (Cu2S) and oxygen (O2).
* Chemical bonds are broken and formed: The process involves breaking the bonds within copper sulfide and between oxygen molecules, and forming new bonds to create copper and sulfur dioxide.
* Irreversible process: The reaction is irreversible, meaning you cannot simply combine copper and sulfur dioxide to get back to the original copper sulfide and oxygen.
In summary: The reaction involves the formation of new substances, breaking and forming chemical bonds, and is irreversible, all of which are hallmarks of a chemical change.
