It means that energy content of one system increased, while the energy content of second system decreased. The total energy (sum of energies in a CLOSED system) is constant. Examples of energy transfer are heat, work and mass transfer.
H2O became a vapor when heated because thats the only one that can go back to its normal state, which is what a physical change is.
Answer:
6 carbon atoms, 12 hydrogen atoms and 6 oxygen atoms
Physical.
cutting a paper in half changes the appearance of the paper.
