Natural gas is methane and it is combined with oxygen to produce carbon dioxide gas and

water. It also release energy that we use to heat our house. The change in enthalpy (AH)

would be

Positive or negative

Negative

Explanation:

Enthalpy changes are heat changes accompanying physical and chemical changes. An enthalpy change is the difference between the sum of the heat contents of products and sum of the heat contents of reactants.

In exothermic change, heat is liberated to the surrounding. The surrounding becomes hotter at the end of the changes.

Enthalpy change is assigned a negative sign as the sum heat contents of products is less than that of the reactants.