Question

Define a chemical reaction. State four observations which
cal reaction. State four observations which help us to determine that a chemical
aken place. Write one example of each observation with a balanced chemical​

Answer 1

Answer:

The transformation of chemical substance into a new chemical substance by making and breaking of bonds between different atoms is known as Chemical Reaction.

4 observations that help us to determine a chemical reaction has taken place are-

1. Change in state.  :-  2H2(g) + O2(g) ------> 2H20(l)

2. Change in colour :- Cu(brown) + O --------> CuO(green)

3. Evolution of gas :- 2NaOH + Zn ------> Na2ZnO2(Sodium zincate) + H2(g)

4. Change in temperature :- 2Zn + 2HCl ---------> 2ZnCl + H2 ( increase in temp.)

Hope it helps :)