Smoke particles in the air typically have masses of the order of kg. The Brownian motion (rapid, irregular movement) of these particles, resulting from collisions with air molecules, can be observed with a microscope. Find the root-mean-square speed of Brownian motion for a particle with a mass of kg in air at K.
Ch 18: Thermal Properties of Matter
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 18, Problem 39a
Compute the specific heat at constant volume of nitrogen (N2) gas, and compare it with the specific heat of liquid water. The molar mass of N2 is g/mol.
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First, understand that the specific heat at constant volume (C_v) for a gas can be calculated using the formula: , where R is the universal gas constant, approximately 8.314 J/(mol·K).
Calculate the specific heat at constant volume for nitrogen gas using the formula: . This will give you the value in J/(mol·K).
Next, convert the specific heat from J/(mol·K) to J/(g·K) for nitrogen gas. Use the molar mass of nitrogen, which is 28.0 g/mol, with the formula: .
For comparison, recall that the specific heat of liquid water is approximately 4.18 J/(g·K). This is a standard value that can be used for comparison purposes.
Finally, compare the specific heat of nitrogen gas in J/(g·K) with that of liquid water. Discuss the differences in specific heat values and consider the implications for energy storage and transfer in these substances.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Specific Heat Capacity
Specific heat capacity is the amount of heat required to change the temperature of a unit mass of a substance by one degree Celsius. It is a crucial property for understanding how different materials absorb and transfer heat. For gases, specific heat can be measured at constant volume or constant pressure, affecting how energy is stored in the substance.
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Molar Mass
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is essential for converting between the mass of a substance and the amount in moles, which is necessary for calculating specific heat capacities in terms of molar quantities. For nitrogen gas (N2), the molar mass is 28.0 g/mol, which helps in determining its specific heat.
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Comparison of States of Matter
Comparing the specific heat of gases and liquids involves understanding the differences in molecular interactions and energy storage. Gases, like nitrogen, have molecules that are more free to move, while liquids, like water, have stronger intermolecular forces. This affects their specific heat values, with liquids generally having higher specific heat due to the energy required to overcome these forces.
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