一條 Physical Science 物理的問題 ( 英文 ) 急急急急急 !!!!!

for a chemical change,

a new substance is formed.

for example, hydrogen reacts with oxygen to form a water molecule.

for a chemical change,

the properties of reactants and product are different.

for example, iron reacts with sulphur to form iron(ll) sulphide. They react with HCL

differently.

for a chemical change,

heat may be absorbed or released in the reaction.

for example, when sodium reacts with water a lot of heat is released.