[Chem]physical/chemical change

1a). Give an example of physical change
Formation of carbon dioxide from dry ice.

1b). Does physical change often accompany with energy change?
no.as dry ice is the solid form of carbon dioxode,so no new subtance is formed and no energy change.

2a) Give an example of chemical change
Put zinc in hydrochloric acid.

2b) Does chemical change often accompany with energy change?
Yes.as hydrogen is formed and it's a new subtance,so the energy changed.

2009-12-25 12:18:46 補充：
but if there is energy change, so what is the energy change?
chemical energy

2009-12-25 12:25:39 補充：
actually...
Does chemical change often accompany with energy change?
both physical change and chemical change are not related to energy change...i study chem for a long time but i never heard physical change and chemical change are accompany with energy change.

2009-12-25 12:28:38 補充：
the process in physical change and chemical change are no energy require.It just a chemical reaction.

2009-12-25 12:46:13 補充：
CORRECTION
2b) Does chemical change often accompany with energy change?
no.although hydrogen is formed and it's a new subtance,chemical change are no energy require.It just a chemical reaction.