Sensor data logging – graphing, smoothing, and calculating ΔH

What it shows

When a salt dissolves in water it either absorbs or releases heat, so the solution cools down or warms up. A temperature probe connected to a data logger records this change over time, and software turns the raw readings into a result: it plots the data, smooths noise with a moving average, finds the extreme temperature and calculates the enthalpy change of solution from ΔH = −m·c·ΔT/n. Because the cup exchanges heat with the room, extrapolating the cooling curve back to the mixing time gives a better ΔT. Both the equipment and the data processing affect accuracy.

How to use

Choose a Solute and press Re-measure, then compare the direction of the temperature change for NH₄NO₃ and for the other two salts. Increase the Sensor noise and toggle Smooth (moving average) to see how the extremum can lock onto a single noisy point. Lower the Sampling rate to show jagged data, then turn on Correct for heat loss and compare the error against the reference value.

Parameters you can change

• Solute NH₄NO₃ (endothermic), Anhydrous CaCl₂ (exothermic), Solid NaOH (exothermic)
• Mass of solute 2–20 g
• Sampling rate 1–10 samples/s
• Sensor noise 0–1 °C

Questions to explore

1. When NH₄NO₃ dissolves, how does the temperature change, and what is the sign of ΔH?
2. Why should noisy data be smoothed before the extreme temperature is read?
3. How does increasing the Mass of solute affect the temperature change and the calculated ΔH per mole?