Experiment 9: Specific Heat Capacity and Calorimetry — Worked Examples

These examples use the method of mixtures and emphasize the difference between an ideal water-only calculation and a corrected energy balance that includes calorimeter heat capacity.

Example 1: Uncorrected specific heat of a metal

A 0.0800 kg0.0800\,\text{kg} metal sample at 95.0∘C95.0^\circ\text{C} is placed in 0.150 kg0.150\,\text{kg} of water initially at 24.0∘C24.0^\circ\text{C}. The equilibrium temperature is 31.0∘C31.0^\circ\text{C}. Neglect calorimeter heat capacity and use cw=4184 J/(kg⋅K)c_w=4184\,\text{J/(kg·K)}. Determine the sample specific heat.

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Example 2: Apply a calorimeter correction

Use the same data as Example 1, but the calorimeter heat capacity is Ccal=35 J/KC_{cal}=35\,\text{J/K}. Determine the corrected specific heat.

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Example 3: Percent error against an aluminum reference

If the reference specific heat for the aluminum sample is 900 J/(kg⋅K)900\,\text{J/(kg·K)}, determine the percent error of the corrected result 906 J/(kg⋅K)906\,\text{J/(kg·K)}.

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Example 4: Determine a calorimeter constant by water mixing

A calorimeter initially contains 0.150 kg0.150\,\text{kg} of water at 22.0∘C22.0^\circ\text{C}. It receives 0.100 kg0.100\,\text{kg} of warm water at 60.0∘C60.0^\circ\text{C}. The final temperature is 36.7∘C36.7^\circ\text{C}. Determine CcalC_{cal}.

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Example 5: Bias caused by sample cooling during transfer

For ms=0.0800 kgm_s=0.0800\,\text{kg}, mw=0.150 kgm_w=0.150\,\text{kg}, Ccal=35 J/KC_{cal}=35\,\text{J/K}, Tw,i=24.0∘CT_{w,i}=24.0^\circ\text{C}, and Tf=31.0∘CT_f=31.0^\circ\text{C}, compare the calculated csc_s if the sample actually enters at 90.0∘C90.0^\circ\text{C} but the experimenter incorrectly substitutes the 95.0∘C95.0^\circ\text{C} bath temperature.

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Example 6: Energy carried by hot bath water on the sample

A wet sample carries 2.0 g2.0\,\text{g} of 95∘C95^\circ\text{C} bath water into a calorimeter that reaches 31∘C31^\circ\text{C}. Estimate the energy released by that unaccounted water.

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Example 7: Predict a final temperature before the experiment

A 0.050 kg0.050\,\text{kg} copper sample with c=385 J/(kg⋅K)c=385\,\text{J/(kg·K)} at 90.0∘C90.0^\circ\text{C} is placed in 0.100 kg0.100\,\text{kg} of water at 25.0∘C25.0^\circ\text{C}. Neglect the calorimeter. Predict the equilibrium temperature.

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Example 8: Sensitivity to final-temperature uncertainty

Using the corrected setup from Example 2, calculate csc_s if the accepted final temperature were 30.8∘C30.8^\circ\text{C} and 31.2∘C31.2^\circ\text{C} instead of 31.0∘C31.0^\circ\text{C}.

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