Do chemical reactions always make new substances?

Yes, chemical reactions *can* make new substances:

* Rearrangement of Atoms: Chemical reactions involve the breaking and forming of chemical bonds between atoms. This rearrangement of atoms leads to the creation of new molecules with different properties. For eksempel, når du brænder træ, kulstof, brint og iltatomer i træet omarrangeres for at danne kuldioxid, vand og aske - stoffer med helt forskellige egenskaber.

However, chemical reactions can also involve:

* Phase Changes: These are physical changes, not chemical changes. Melting ice (solid water) into liquid water or boiling water into steam (gaseous water) does not create new substances. The water molecules remain H₂O.

* Mixing: Mixing substances like sugar and water creates a solution, but the sugar and water molecules themselves remain unchanged.

To summarize:

* Chemical reactions *can* and often *do* form new substances by rearranging atoms.

* Some reactions involving phase changes or mixing do not form new substances.

So, it depends on the specific chemical reaction!