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Enthalpy Change Formula:
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Enthalpy change (ΔH) is a thermodynamic quantity representing the total heat content of a system at constant pressure. It measures the energy absorbed or released during a chemical reaction or physical process.
The calculator uses the enthalpy change formula:
Where:
Explanation: This formula calculates the energy required to change the temperature of a substance when no phase change occurs.
Details: Enthalpy calculations are essential in thermodynamics, chemical engineering, and materials science for designing heating/cooling systems, predicting reaction energies, and understanding energy transfer processes.
Tips: Enter mass in kilograms, specific heat in J/kg·K, and temperature change in Kelvin. All values must be positive numbers.
Q1: What's the difference between enthalpy and heat?
A: Enthalpy is a state function that includes internal energy plus pressure-volume work, while heat is energy transferred due to temperature difference.
Q2: Can this formula be used for phase changes?
A: No, this formula only applies to temperature changes without phase transitions. For phase changes, use ΔH = m × L (where L is latent heat).
Q3: Why use Kelvin instead of Celsius?
A: Kelvin is an absolute temperature scale where 0 represents absolute zero, making it appropriate for thermodynamic calculations involving temperature differences.
Q4: What are typical specific heat values?
A: Water has Cp = 4186 J/kg·K, aluminum ≈ 900 J/kg·K, iron ≈ 450 J/kg·K. Values vary significantly between materials.
Q5: How does pressure affect enthalpy calculations?
A: This simple formula assumes constant pressure. For precise calculations under varying pressure conditions, more complex thermodynamic relationships are needed.