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Ch.2 - Atoms & Elements
Chapter 2, Problem 143

A volatile liquid (one that easily evaporates) is put into a jar and the jar is then sealed. Does the mass of the sealed jar and its contents change upon the vaporization of the liquid?

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1
Identify the principle of conservation of mass, which states that mass is neither created nor destroyed in a closed system.
Recognize that the jar is sealed, making it a closed system where no mass can enter or leave.
Understand that when the liquid evaporates, it changes from a liquid to a gas, but the total mass of the liquid and gas remains the same.
Acknowledge that the mass of the jar and its contents is the sum of the mass of the jar, the liquid, and the vapor.
Conclude that since no mass is lost or gained in the sealed jar, the mass of the sealed jar and its contents does not change upon vaporization.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Volatility and Vaporization

Volatility refers to the tendency of a substance to vaporize, which is influenced by its intermolecular forces. A volatile liquid easily transitions from a liquid to a gas at room temperature. When a volatile liquid is placed in a sealed jar, it will evaporate until it reaches equilibrium, where the rate of evaporation equals the rate of condensation.
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Conservation of Mass

The law of conservation of mass states that mass cannot be created or destroyed in a closed system. In the context of the sealed jar, even though the liquid evaporates, the total mass of the jar and its contents remains constant. The mass of the vapor produced is equal to the mass of the liquid that has evaporated, ensuring that the overall mass does not change.
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Equilibrium in Closed Systems

In a closed system, such as a sealed jar, dynamic equilibrium can be established between the liquid and its vapor. At this point, the rate of evaporation of the liquid equals the rate of condensation of the vapor back into the liquid. This equilibrium does not affect the total mass of the system, as all molecules remain contained within the jar.
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