Chemical you are breaking down the water and it would need to under go another chemical change to become water again.
It is always chemistry which breaks down molecules (H2O) into its elements (H2 and O2)
CHEMICAL CHANGE qYES
No, it is a physical change.
No. Elements cannot be broken down by chemical means, compounds can. Some substances in the cereal may dissolve in water, but they do not break down. Once you eat and start digesting the cereal, then...