Which equation represents a physical change?
(1) H2O(s) + 6.01 kJ ==>H2O(l)
(2) 2H2(g) + O2(g) ==>2H2O(g) + 483.6 kJ
(3) H2(g) + I2(g) + 53.0 kJ ==>2HI(g)
(4) N2(g) + 2O2(g) + 66.4 kJ ==> 2NO2(g)