If heat is escaping from the calorimeter when the water and unknown material are combined, then which of the following statements is true?

• A. The calculated change in internal energy (ΔU) will be unaffected.
• B. The calculated change in internal energy (ΔU) will be greater than the actual value.
• C. The calorimeter will measure the exact amount of heat exchanged.
• D. The calculated change in internal energy (ΔU) will be less than the actual value.

Answer: (D)

Verified step by step guidance

1. Understand that in a calorimetry experiment, the system is assumed to be isolated so that no heat escapes to the surroundings, allowing accurate measurement of heat exchange.
2. Recognize that if heat escapes from the calorimeter, the measured heat change will be less than the actual heat change because some heat is lost and not detected.
3. Recall that the change in internal energy (\$\Delta U\$) is related to the heat exchanged at constant volume by the equation \$\Delta U = q_v\$, where \$q_v\$ is the heat at constant volume.
4. Since the calorimeter measures less heat due to loss, the calculated \$\Delta U\$ based on this measurement will be smaller than the true \$\Delta U\$ of the system.
5. Therefore, the statement that the calculated change in internal energy (\$\Delta U\$) will be less than the actual value is correct because heat loss causes an underestimation of the energy change.