The equation that shows a chemical change is:
C3H8 + 5O2 → 3CO2 + 4H2O
This equation represents the combustion of propane (C3H8) in the presence of oxygen (O2), resulting in the formation of carbon dioxide (CO2) and water (H2O). This involves breaking and forming bonds, which is characteristic of a chemical change.
The other equations represent physical changes (phase changes) where the chemical identity of the substances remains the same:
- C2H5OH(l) → C2H5OH(g) (liquid to gas)
- NH3(g) → NH3(l) (gas to liquid)
- H2O(s) → H2O(g) (solid to gas)