Determine the specific latent heat of fusion of ice (L_f) using the calorimetric method of mixtures, observing the temperature depression resulting from the melting of dried ice chips in warm water inside a calibrated copper calorimeter, and evaluating the thermal energy conservation balance with Rumford radiation compensation. Explore a virtual apparatus, collect readings and analyse a graph.
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Adjust the apparatus, then take a reading.
Readings are generated by an ideal model. The diagram is schematic and is not to scale.
The teaching simulation models the melting of pure ice under ideal thermal conditions with constant initial warm water temperature T_0 = 30.00 °C, ice temperature T_ice = 0.00 °C, and an invariant system heat capacity C_sys = 866.08 J K⁻¹. In physical experiments, residual surface water film adhering to ice chips can cause negative systematic errors, using freezer ice below 0 °C causes positive errors, water splashing during ice transfer reduces the effective mass, evaporation from the warm surface during dissolution introduces unmodelled cooling, and small departures from symmetric Rumford compensation leave residual radiation exchanges with the room. The simulation evaluates equilibrium temperatures using the exact thermodynamic conservation relation T_f = (C_sys T_0 − m_i L_f) / (C_sys + m_i c_w), where m_i is the dry ice mass in kilograms, L_f = 334,000 J kg⁻¹ (334.00 kJ kg⁻¹) is the reference latent heat of fusion of ice, c_w = 4,186 J kg⁻¹ K⁻¹ is the specific heat capacity of water, T_0 = 30.00 °C is the initial warm water temperature, and C_sys = 866.08 J K⁻¹ is the aggregate thermal capacity. Equilibrium temperatures are rounded to 0.01 °C to simulate precision calorimetric thermometry, and ordinary least-squares regression of Q_net against m_i yields the reported latent heat of fusion.
A thin-walled specularly polished copper container (mass 75.0 g, volume 250 mL) supported on low-conductivity vulcanized cork pegs inside a concentric air jacket, sealed with a wooden lid featuring apertures for the thermometer and stirrer to minimize environmental heat exchange.
A sensitive mercury-in-glass thermometer graduated from 10 °C to 45 °C in 0.05 °C divisions, immersed centrally in the water bath to measure the initial warm temperature T_0 and track the cooling descent to the final equilibrium minimum T_f.
A low-thermal-mass brass wire stirrer formed into an open horizontal loop encircling the thermometer, used to gently circulate the water bath vertically to promote rapid melting and prevent thermal stratification.
A clean watch glass holding crushed melting ice chips, paired with laboratory tweezers and sheets of dry lint-free filter paper used to blot each ice fragment completely free of surface water film immediately before immersion.
Determine the specific latent heat of fusion of ice (L_f) using the calorimetric method of mixtures, observing the temperature depression resulting from the melting of dried ice chips in warm water inside a calibrated copper calorimeter, and evaluating the thermal energy conservation balance with Rumford radiation compensation. Suggested independent settings: 15.0, 20.0, 25.0, 30.0, 35.0 g.
Weigh the clean, dry copper calorimeter vessel together with its brass loop stirrer to ±0.01 g on an analytical balance. Add exactly 200.00 g of distilled water warmed to approximately 32 °C. Place the calorimeter inside the protective air jacket and seat the wooden lid firmly.
Preparing the warm water near 30 °C to 32 °C ensures that after the ice melts, the final equilibrium temperature will fall roughly as far below room temperature (20 °C) as the initial water was above it, executing Rumford radiation compensation.
Crush clean, clear ice into small fragments (approximately pea to hazelnut size). Place the ice in a funnel or watch glass and allow it to drain until melting commences freely, establishing a true equilibrium ice-water mixture at 0.00 °C. Spread several dry filter paper sheets nearby.
Small ice fragments possess a high surface-area-to-volume ratio, facilitating rapid dissolution and reducing the duration of environmental heat exchange. Allowing ice to begin melting confirms its temperature is strictly 0.00 °C rather than sub-zero freezer ice.
Insert the precision thermometer into the calorimeter water through the lid aperture. Agitate the bath with gentle vertical strokes of the stirrer until the temperature stabilizes. Record the steady initial warm temperature T_0 = 30.00 °C.
Accurate initial temperature recording sets the exact thermal baseline from which the sensible heat release of the calorimeter and warm water is evaluated.
Take an ice chip with clean tongs, press it firmly between dry filter paper sheets to remove all adhering liquid water film, and drop it immediately into the calorimeter without splashing. Repeat swiftly until the target ice mass (e.g., 15.0 g) has been introduced, closing the lid immediately between additions.
Thorough blotting is critical: any adhering liquid water is already melted and absorbs zero latent heat of fusion, which would cause an apparent deficit in the calculated latent heat value.
Stir the water bath continuously and smoothly with the helical stirrer, watching the thermometer meniscus through an optical magnifier. Track the temperature depression as the ice chips dissolve. Record the lowest stationary temperature attained before environmental re-warming begins as the equilibrium temperature T_f.
Continuous stirring enforces thermal homogeneity, ensuring the thermometer bulb records the true bulk mixture temperature and identifies the exact moment of complete ice dissolution.
Remove the calorimeter vessel and reweigh it to ±0.01 g. Determine the exact mass of ice added m_i = m_final − m_initial. Repeat the measurement across five distinct ice charges (15.0 g, 20.0 g, 25.0 g, 30.0 g, and 35.0 g). For each run, compute Q_net = C_sys (T_0 − T_f) − m_i c_w T_f in joules. Plot Q_net against m_i (kg) and evaluate L_f from the slope of the regression line.
Gravimetric reweighing provides an exact record of the dissolved ice mass, while regression across multiple charges eliminates single-trial timing and weighing anomalies.
Points are your observations. The fit uses SI x and y values before display scaling.
| # | Mass of dry ice m_i (g) | Equilibrium temperature T_f (°C) | Mass of dry ice m_i (kg) | Net latent heat absorbed Q_net (J) | Remove |
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