Law of Conservation of Mass: Introducing Stoichiometry (LC 2027) (Leaving Cert Chemistry): Flashcards

Change in appearance without forming new substances

Remain unchanged

Physical - still $H_2O$

Formation of one or more new substances

Colour change, gas, heat/light, precipitates

Iron oxide from iron + oxygen

No - material remains chemically identical

Easy to reverse

Yes - completely different materials created

Difficult or impossible to reverse

Heat, light, or sound often produced

Physical - still $H_2O$

Chemical - new substances (ash, gases) form