Question

state any 3 observations which help to determine whether a chemical reaction has taken place . write an activity which justify at least 2 of the listed observations

Answer 1

some observations noticed when a chemical reaction takes place are:

1. Change in state
2. Change in colour
3. evolution of gas

• A chemical reaction  in which change is state takes place is;

Ammonia gas reacts with hydrogen chloride gas to produce solid ammonium chloride.

NH3 (g) + HCl (g) = NH4Cl (s)

• Change in colour example:

Reaction of iron and copper sulphate

CuSO4+Fe=FeSO4+Cu

Colour changes from blue to light green.

• Evolution of gas:

Zn + H2SO4 = ZnSO4 + H2

   Hope it helps