Which balanced chemical equation best represents the thermal decomposition of sodium bicarbonate? NaHCO3 (s) → NaOH (s) + CO2 (g) 2NaHCO3 (s) → Na2CO3 (s) + CO2 (g) + H2O (g)
2NaHCO3 (s) → Na2O (s) + 2CO2 (g) + H2O (g) NaHCO3 (s) → NaH (s) + CO (g) + O2 (g)

As you can see from the calculations, 2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g) was the reaction that happened when heating the NaHCO3 because its theoretical mass from the equation is almost exactly the same as the actual mass of the product from the experiment.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.