Water is made of two hydrogen atoms and one oxygen atom bonded together. Julia is describing how water undergoes a physical chan
ge when it boils. She says that the particles shift to be farther apart and that the oxygen and hydrogen separate. She also says that the total mass of the steam is the same as the initial water, and that heat energy was required to cause the change. She finishes her description by saying that the steam can be turned back into water if it is cooled. Which is the mistake in her description?
Julio is correct on everything else except that during the boiling of water, the oxygen atom separates from the two hydrogen atoms in each water molecule. Boiling is a physical change. Only physical properties of water change i.e changing from being a liquid to a guess. Its chemical properties remain the same. It is still water, H20. Its chemistry must not be changed in a a physical change like boiling. Once oxygens separate from hydrogens that and one oxygen atom bonded together. Julia is describing how water undergoes a physical change when it boils. She says that the particles shift to be farther is an entirely different substance, not water.
A mold forms when hard parts of an organism are buried in sediment; the hard parts completely dissolve over time, leaving behind a hollow area. A cast forms as a result of a mold when minerals and sediment fill in the impression.
