Chemical reaction help

2H2O -> 2H2 + O2

2Mg + O2 -> 2MgO

CuCl2 -> Cu+Cl2

2H2O2 -> 2H2O + O2

CaO + H2O -> Ca(OH)2

For each reaction, what evidence is there that a chemical change has occurred?

2H2O -> 2H2 + O2
(a liquid produces gases H2 & O2)

2Mg + O2 -> 2MgO
a silvery metal produces a white powder, MgO
, lots of heat, light & sparks

CuCl2 -> Cu(s)+Cl2(g)
a green compound produces a yellow gas, Cl2
& a reddish solid, Cu

2H2O2 -> 2H2O + O2
lots of bubbles are produced, (O2)


CaO + H2O -> Ca(OH)2
when CaO reacts with water, it produces lots of heat