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Specific Heat Calculator

Find the heat needed to change a temperature.

Result

167,440.00 J

How it is calculated

The tool multiplies three numbers: Q = m × c × ΔT, where m is the mass, c is the specific heat capacity and ΔT is the temperature change (final minus initial). The result is labelled in joules, so the units must match: mass in kg with c in J/(kg·K), or mass in g with c in J/(g·K). A change of 1 °C equals a change of 1 K.

The tool does no unit conversion and applies no checks beyond requiring all three numbers. A negative ΔT, a cooling, gives a negative Q, meaning heat is released. It assumes c stays constant over the temperature range and ignores phase changes such as melting or boiling, where extra latent heat is involved. It also ignores heat lost to the container or surroundings.

Worked example

Heat 2 kg of water by 20 °C, using c = 4186 J/(kg·K).

Q = 2 × 4186 × 20. First 2 × 4186 = 8372, then 8372 × 20 = 167,440. The result is 167,440.00 J, about 167 kJ. Cooling the same water by 20 °C (ΔT = −20) gives −167,440.00 J: the same amount of energy leaves the water.

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Common mistakes

  • Mixing grams with a per-kilogram specific heat, or the reverse. 2000 g with 4186 J/(kg·K) gives a result 1000 times too large.
  • Entering the final temperature instead of the change. ΔT is final minus initial, so heating from 15 to 35 °C is 20, not 35.
  • Entering the sign of ΔT the wrong way round. Heating is positive and cooling is negative, which changes the sign of Q.
  • Using this for a substance that melts or boils within the range. The formula covers only temperature change; it leaves out the energy of the phase change.
  • Using the specific heat of one material for another. Water and metals differ by a large factor, so use the value for your substance.

About this calculator

This calculator finds heat energy using Q = mcΔT — mass times the material's specific heat capacity times the change in temperature — the standard formula for how much energy it takes to heat or cool a substance by a given amount, in either direction.

Chemistry students use it in calorimetry lab problems to find heat released or absorbed in a reaction, engineers use it to size heaters, boilers, or cooling systems, and it's the same reasoning cooks apply, less formally, when noting that water takes far more heat to warm than oil because of water's high specific heat capacity.

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Comments (1)

  • Editorial team

    Joules are rarely the unit you pay for. Divide by 3,600,000 to get kilowatt-hours: the 167,440 J needed to warm 2 kg of water by 20 °C is only about 0.047 kWh. The result is the ideal energy into the substance, so a real kettle or heater needs more because of losses. A change of 1 °C equals a change of 1 K, so either works for ΔT. Which material are you heating?

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