Enthalpy (Heat) Calculator
Enter mass, specific heat and temperature change to find the heat energy, q = mcΔT.
The heat energy gained or lost by a substance is q = mcΔT — mass times specific heat capacity times the temperature change. Heating 100 g of water (specific heat 4.18 J/g°C) by 10°C requires 100 × 4.18 × 10 = 4,180 joules. A positive result absorbs heat; a negative one releases it.
How to Use This Calculator
Enter the mass of the substance in grams, its specific heat capacity in joules per gram per degree Celsius, and the temperature change. The calculator returns the heat energy in joules (and kilojoules). Water's specific heat is 4.18 J/g°C, a common default.
This is the calorimetry equation, used to find how much heat a substance absorbs when warmed or releases when cooled. A positive temperature change means heat absorbed; a negative one means heat released.
How the Calculation Works
The heat energy depends on three things: how much substance there is (mass), how resistant it is to temperature change (specific heat capacity), and how much its temperature actually changes. Multiplying them gives the energy transferred.
Specific heat is the energy needed to raise one gram by one degree; water's high value of 4.18 J/g°C is why it heats and cools slowly. The sign of ΔT tells you the direction — heat in or heat out.
q = m × c × ΔT
Worked Example
To heat 100 g of water by 10°C: q = 100 × 4.18 × 10 = 4,180 joules, or 4.18 kJ.
If that same water instead cooled by 10°C, ΔT would be −10 and q would be −4,180 J, meaning 4,180 joules were released.
Assumptions and Limitations
- Uses q = mcΔT for a single phase (no melting or boiling)
- Specific heat is assumed constant over the temperature range
- Mass in grams, specific heat in J/g°C, ΔT in °C → q in joules
- Phase changes need latent heat, a separate calculation
When to Use an Enthalpy Calculator
Chemistry students use this to find the heat energy from mass, specific heat, and temperature change. Run it for calorimetry homework and lab write-ups, or to check an energy calculation. Enter the three values to get the heat absorbed or released, with the sign explained.
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Open calculator →Frequently Asked Questions
What is the formula for heat energy?
q = mcΔT — mass times specific heat capacity times temperature change. It gives the heat absorbed or released by a substance that changes temperature without changing phase.
What is specific heat capacity?
The energy needed to raise one gram of a substance by one degree Celsius. Water's is 4.18 J/g°C, which is high, so water stores and releases a lot of heat for its mass.
What does a negative q mean?
It means heat is released rather than absorbed, which happens when the temperature change is negative (the substance cools). A positive q means heat is absorbed as it warms.
Does q = mcΔT work for melting or boiling?
No. During a phase change the temperature stays constant, so ΔT is zero and this formula gives zero. Phase changes use latent heat (q = mL) instead.
Is this the same as enthalpy change?
At constant pressure, the heat q equals the enthalpy change ΔH, which is why this calorimetry formula is used to measure enthalpy changes in the lab.
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