Passage
A student performed an experiment to determine the energy content of a sample of potato chips. The chips were blended and then freeze-dried to remove moisture from the sample. Freeze-drying, or lyophilisation, is the preferred dehydration process for food calorimetry due to its minimal impact on nutritional content. Lyophilisation removes water from frozen food samples at low pressure through sublimation. The water is later collected in a cooled condensation chamber to prevent damage to any electric components.After freeze-drying, the sample was ground into a dry homogenous powder. A 1-g sample of the powder was placed in a bomb cell, an enclosed steel-walled container, and pressurized to 25 atm with pure oxygen to ensure complete combustion. The bomb cell was submerged in 500 g of water at room temperature (25°C) in an enclosed and thermally insulated calorimetry device. The sample was combusted using an electric fuse. The temperature of the surrounding water was measured with a glass thermometer every 30 s for several minutes (Figure 1) .
Figure 1 Temperature of the water in the bomb calorimeterThe energy content of food is given in units of dietary calories (Cal) , which is equal to 4.185 kJ, or 1,000 gram calories (cal) . A gram calorie is the amount of energy required to increase 1 g of water by 1°C.
Adapted from Jumpertz R, Venti CA, Le DS, et al., Food label accuracy of common snack foods. Obesity 2013 Wiley-Blackwell.
-The bomb cell and the calorimetry device used in the experiment are what types of thermodynamic systems?

Question

Passage
A student performed an experiment to determine the energy content of a sample of potato chips. The chips were blended and then freeze-dried to remove moisture from the sample. Freeze-drying, or lyophilisation, is the preferred dehydration process for food calorimetry due to its minimal impact on nutritional content. Lyophilisation removes water from frozen food samples at low pressure through sublimation. The water is later collected in a cooled condensation chamber to prevent damage to any electric components.After freeze-drying, the sample was ground into a dry homogenous powder. A 1-g sample of the powder was placed in a bomb cell, an enclosed steel-walled container, and pressurized to 25 atm with pure oxygen to ensure complete combustion. The bomb cell was submerged in 500 g of water at room temperature (25°C) in an enclosed and thermally insulated calorimetry device. The sample was combusted using an electric fuse. The temperature of the surrounding water was measured with a glass thermometer every 30 s for several minutes (Figure 1) .

Figure 1 Temperature of the water in the bomb calorimeterThe energy content of food is given in units of dietary calories (Cal) , which is equal to 4.185 kJ, or 1,000 gram calories (cal) . A gram calorie is the amount of energy required to increase 1 g of water by 1°C.
Adapted from Jumpertz R, Venti CA, Le DS, et al., Food label accuracy of common snack foods. Obesity 2013 Wiley-Blackwell.
-The bomb cell and the calorimetry device used in the experiment are what types of thermodynamic systems?

Quizplus · Accepted Answer

11ecba2d_12fa_e5d1_a3bf_61091541cd75_MD0008_00 In thermodynamics, the "system" is the physically enclosed space being studied that is separated from the rest of the universe, known as the "surroundings." There are three main types of thermodynamic systems, which are characterized by the type of barrier between the system and its surroundings: An open system allows heat and matter to be exchanged with the surroundings. A closed system allows heat but not matter to be exchanged with the surroundings. An isolated system does not allow heat or matter to be exchanged. According to the passage, the bomb cell houses the combustion reaction, and its surroundings include the water in the calorimetry device. Because the temperature of the surrounding water increased during the combustion reaction, heat can be exchanged between the bomb cell and its surroundings. Because the container is enclosed and does not allow for the exchange of matter, the bomb cell is an example of a closed system (Choices B and D). The calorimetry device houses the bomb cell and the water it is submerged in, and its surroundings are the surface it rests on and the nearby air. Because the enclosed walls of the device are thermally insulated (poor conductors of heat), neither heat nor matter can be exchanged with its surroundings, and the device is an example of an isolated system (Choice A). Educational objective: An open system allows heat and matter to be exchanged with the surroundings. A closed system allows heat but not matter to be exchanged with the surroundings. An isolated system does not allow heat or matter to be exchanged with the surroundings.

Passage A Student Performed an Experiment to Determine the Energy Content