A different mixture is formed in each case. A different solution is formed in each case. Both a change of state and of elements is involved. New molecules are formed but the same elements exist.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Oxygen reacts with iron to produce rust and with hydrogen to produce water. Which statement describes both reactions?
Possibilities:
- A different mixture is formed in each case.
- A different solution is formed in each case.
- Both a change of state and of elements is involved.
- New molecules are formed but the same elements exist.

New molecules are formed but the same elements exist.