Calculate the heat energy required to melt a substance at its melting point.
This calculator is designed to help you estimate the amount of heat energy needed to melt a specific mass of a substance. It uses the enthalpy of fusion (also called the heat of fusion) for the substance you choose. All you need to do is enter the mass, select the substance, and the calculator will estimate the energy required for the phase change from solid to liquid.
The process is straightforward. The calculator assumes the substance is already at its melting point, and it calculates the energy needed to complete the melting process without any temperature change.
The key concept here is that enthalpy of fusion represents the energy required to change a substance from solid to liquid at its melting point. Because this change happens at constant temperature, the calculation is simply a multiplication of mass and the ΔHf value.
It’s important to remember that the calculator does not account for heating the substance up to its melting point. If your material starts at a temperature lower than its melting point, you will need to include additional energy for heating, which is calculated using the specific heat capacity.
The calculator is especially useful for common materials such as water or ethanol. For example, the heat of fusion for ice is 334 J/g. This means that melting 1 gram of ice at 0°C requires 334 joules of energy.
Ethanol has a lower enthalpy of fusion at 108 J/g, which means it takes less energy to melt compared to water. This difference is why different substances behave differently during phase changes, and why knowing the enthalpy of fusion is helpful in both lab and real-world settings.
| Substance | ΔH_f (J/g) | Melting Point (°C) | Source |
|---|---|---|---|
| Water (H₂O) | 334 | 0 | NIST |
| Ice (solid H₂O) | 334 | 0 | NIST |
| Ethanol (C₂H₅OH) | 108 | -114 | NIST |
| Benzene (C₆H₆) | 126 | 5.5 | NIST |
| Sodium Chloride (NaCl) | 2100 | 801 | NIST |
| Sulfur (S) | 1700 | 115.2 | NIST |
| Lead (Pb) | 4800 | 327.5 | NIST |
| Aluminum (Al) | 397 | 660.3 | NIST |
| Copper (Cu) | 205 | 1984 | NIST |
| Mercury (Hg) | 11790 | -38.83 | NIST |
| Gallium (Ga) | 5590 | 29.76 | NIST |
| Iron (Fe) | 272 | 1538 | NIST |
| Silver (Ag) | 11000 | 961.8 | NIST |
| Zinc (Zn) | 115 | 419.5 | NIST |
| Acetic Acid (C₂H₄O₂) | 186 | 16.6 | NIST |
| Cholesterol (C₂₇H₄₆O) | 150 | 148 | NIST |
| Stearic Acid (C₁₈H₃₆O₂) | 200 | 69.3 | NIST |
| Cocoa Butter (C₅₃H₉₈O₆) | 200 | 33 | NIST |
| Lactose (C₁₂H₂₂O₁₁) | 340 | 202-203 | NIST |
| Glycine (C₂H₅NO₂) | 120 | 75.5 | NIST |
The enthalpy of fusion is the amount of energy needed to turn a solid into a liquid at its melting point. During this change, the temperature remains constant while the structure of the material rearranges into a liquid form.
The calculation uses the formula: q = mass × ΔHf. Here, q represents the heat energy required, mass is in kilograms, and ΔHf is the enthalpy of fusion in J/g.
Yes. You can select from the listed substances, or choose “Other” and enter your own ΔHf value. This makes the calculator flexible for a wide range of materials and lab applications.
Common values include water (334 J/g) and ethanol (108 J/g). These values are widely used in chemistry and engineering to estimate energy requirements during melting.
Check out other thermodynamics calculators available on our site: Thermodynamics calculators.