i thought the hydrogen was ignited instead of turned into vaporsYes, chemical changes can occur without any visible changes in appearance. For example, the rusting of iron is a chemical change, but it may not be noticeable until the iron has completely corroded.
Yes, physical changes can sometimes be mistaken for chemical changes. For instance, melting or freezing of a substance does not change its chemical composition, but changes in color or smell can indicate a chemical change.
Yes, a chemical change always results in the formation of a new substance with different chemical properties. This is because the atoms and molecules in the original substance are rearranged to form new compounds.
Some common signs of a chemical change include the formation of a gas, a change in color or odor, the release or absorption of heat, and the formation of a precipitate. However, it is important to use scientific methods and observations to confirm a chemical change.
Some common examples of chemical changes include combustion, oxidation, fermentation, and photosynthesis. Other examples include the formation of rust, cooking food, and digesting food in our bodies.