Question

Describe the ways you can know that a chemical reaction has occurred. Enter your answer in the space provided.

Answer 1

Answer: A chemical reaction is one in which rearrangement of atoms take place. A chemical reaction is characterized by following changes:

1) Absorption or release of heat. Example: Combustion reaction

$CH_4+2O_2\rightarrow CO_2+2H_2O$

2) formation of gas bubbles

$Mg+2HCl\rightarrow MgCl_2+H_2(g)$

3) Formation of precipitate

$2AgNO_3(aq)+Ba(Cl)_2(aq)\rightarrow 2AgCl(s)+Ba(NO_3)_2(aq)$

4) Change in color

$2Mg+O_2\rightarrow 2MgO$

Colorless $Mg$ changes to white $MgO$