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Calorimetry Calculator

Calculate heat absorbed or released using q = mcDeltaT. Enter the mass, initial and final temperatures, and select a substance (or enter a custom specific heat).

Calorimetry and q = mcΔT

The calorimetry equation is a one-line accounting of heat transfer: how much energy entered or left a sample of known mass and known specific heat, given how much its temperature changed.

q = m · c · ΔT

The calculator takes mass (g), specific heat (J/g·K) — picked from a list of common substances or entered directly — and the initial and final temperatures. It computes ΔT, multiplies through, and returns q in both joules and kilojoules.

The sign matters. Compute ΔT as T_final − T_initial. If the substance warmed, ΔT is positive and q is positive: the substance absorbed heat. If it cooled, q is negative: the substance released heat. In a typical coffee-cup experiment, the water is the surroundings, so a positive q for the water means the reaction (the system) released that same amount of heat — q_reaction = −q_water. This sign flip is the most common place students lose track.

Specific heat values vary by an order of magnitude across common substances. Water at 4.184 J/(g·K) is the high end; metals run around 0.4 to 0.9. That’s why a small mass of hot metal dropped into water barely shifts the water temperature but cools dramatically itself: the same amount of heat moves between them, but the metal’s lower heat capacity means it absorbs a much bigger ΔT per joule.

For the equation to work, the substance has to stay in one phase across the temperature range. If it melts, freezes, boils, or condenses, you also need to add the latent heat (q = m·ΔH_fus or m·ΔH_vap) at the phase transition.

Worked examples

Heating water: warm 250.0 g of water from 20.0 to 85.0 °C. ΔT = 65.0 K, q = 250.0 × 4.184 × 65.0 = 67,990 J = 67.99 kJ absorbed.

NaOH dissolving: 100.0 g of water rises from 22.0 to 29.5 °C. q_water = 100.0 × 4.184 × 7.5 = 3,138 J absorbed by water, so the dissolution released about 3.14 kJ (ΔH negative, exothermic).

Cooling copper: 50.0 g of Cu (c = 0.385) cools from 95.0 to 25.0 °C. ΔT = −70.0 K, q = 50.0 × 0.385 × (−70.0) = −1,348 J — the copper released 1,348 J into its surroundings.

Frequently Asked Questions

What is calorimetry?
Calorimetry is measuring heat flow by tracking temperature change in a substance of known mass and known specific heat — almost always water in introductory work. The reaction or phase change you care about happens inside (or in thermal contact with) the water; the water's temperature change tells you how much heat moved. Coffee-cup calorimeters measure heat at constant pressure (so q equals ΔH); bomb calorimeters measure at constant volume (so q equals ΔU).
What does q = mcΔT mean?
q is heat in joules, m is mass in grams, c is specific heat in J/(g·K), and ΔT is final temperature minus initial. The product mc is the heat capacity of the sample — the joules needed per kelvin of warming. Multiply by ΔT and you get total heat transferred. Sign convention: positive q means the sample absorbed heat, negative means it released heat. Whether the reaction is endo- or exothermic depends on whose perspective you're taking.
What is specific heat capacity?
Specific heat is the heat needed to warm one gram of a substance by one kelvin. Water's value of 4.184 J/(g·K) is the highest among common substances — hydrogen bonding stores a lot of energy as you raise the temperature. Metals are roughly an order of magnitude lower (Cu = 0.385, Al = 0.897), which is why a hot copper bar cools fast in water and barely warms the water in the process.
How do you tell if a reaction is exothermic or endothermic from calorimetry?
If the solution warms up, heat flowed from the reaction into the water, so the reaction itself released heat — exothermic, ΔH negative. If the solution cools down, heat flowed from the water into the reaction, so the reaction absorbed heat — endothermic, ΔH positive. The sign of ΔT for the surroundings is opposite to the sign of ΔH for the system.
Why is water used in most calorimetry experiments?
Water's specific heat is high, well-characterized, and nearly constant from 0 to 100 °C, so a small temperature change corresponds to a large amount of heat — meaning small reactions are still measurable. It's also cheap, non-toxic, and compatible with most aqueous reactions, so the substance you're measuring and the medium absorbing the heat are often the same liquid.