Explain what enthalpy is. Why do we need to include a positive or negative sign with the enthalpy change?

Enthalpy /ˈɛnθəlpi/ ( listen) is a property of a thermodynamic system, defined as the sum of the system's internal energy and the product of its pressure and volume. It is a convenient state function preferred in many measurements in chemical, biological, and physical systems at a constant pressure.

Explanation:

Endothermic processes require an input of energy to proceed and are signified by a positive change in enthalpy. Exothermic processes release energy upon completion, and are signified by a negative change in enthalpy.

The sign of q for an endothermic process is positive because the system is gaining heat. A chemical reaction or physical change is exothermic if heat is released by the system into the surroundings.

Explanation:

Because the surroundings is gaining heat from the system, the temperature of the surroundings increases.

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