Explanation:
A chemical reaction where heat energy is absorbed by the reactant molecules is known as an endothermic reaction.
For example, [tex]A + B + Heat \rightarrow AB[/tex]
The value of = +ve for an endothermic reaction.
On the other hand, a chemical reaction in which heat energy is released by the reactant molecules is known as an exothermic reaction.
For example, [tex]C + D \rightarrow CD + Heat[/tex] is an exothermic reaction.
The value of [tex]\Delta H[/tex] = -ve for an endothermic reaction.
For example, burning of natural gas in a stove exothermic as heat is being released that is used to cook the food.
Hence, the sign of energy change for this reaction is negative.
Thus, we can conclude that the burning of natural gas in a stove exothermic reaction and the sign of energy change is negative.