As a metal such as lead melts, what happens to (a) the average kinetic energy of the atoms? (b) the average distance between the atoms?

Name: Chemistry: The Central Science
Author: Brown
ISBN: 9780137542970

Verified step by step guidance

Step 1: Understand that melting is a phase change from solid to liquid, which occurs at a constant temperature for a pure substance.

Step 2: Recognize that during melting, the temperature remains constant, so the average kinetic energy of the atoms, which is directly related to temperature, does not change.

Step 3: Consider the structure of a solid, where atoms are closely packed in a fixed arrangement, and compare it to a liquid, where atoms are more loosely arranged and can move past each other.

Step 4: Realize that as the metal melts, the rigid structure breaks down, allowing atoms to move more freely, which increases the average distance between them.

Step 5: Conclude that during melting, while the average kinetic energy of the atoms remains constant, the average distance between the atoms increases as the solid structure transitions to a liquid state.

Key Concepts

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

Kinetic Energy and Temperature

Kinetic energy is the energy of motion, and in the context of atoms, it relates to their temperature. As a substance heats up, the average kinetic energy of its atoms increases, leading to more vigorous motion. This is crucial for understanding phase changes, such as melting, where the temperature rises until the solid structure breaks down.

Phase Changes

Phase changes refer to the transitions between solid, liquid, and gas states of matter. During melting, a solid absorbs heat, causing its atoms to gain kinetic energy and move apart, transitioning into a liquid state. This process illustrates how energy input affects the arrangement and behavior of atoms in different phases.

Interatomic Forces

Interatomic forces are the attractive and repulsive forces between atoms that determine the structure and stability of a material. In solids, these forces keep atoms closely packed. As a metal like lead melts, these forces weaken, allowing atoms to move further apart, which increases the average distance between them and facilitates the transition to a liquid state.

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Related Practice

Textbook Question

At standard temperature and pressure, the molar volumes of Cl₂ and NH₃ gases are 22.06 and 22.40 L, respectively. (c) The densities of crystalline Cl₂ and NH₃ at 160 K are 2.02 and 0.84 g/cm³, respectively. Calculate their molar volumes.

Textbook Question

(a) How does the average kinetic energy of molecules com- pare with the average energy of attraction between mole- cules in solids, liquids, and gases?

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Textbook Question

At standard temperature and pressure, the molar volumes of Cl₂ and NH₃ gases are 22.06 and 22.40 L, respectively (b) On cooling to 160 K, both substances form crystalline solids. Do you expect the molar volumes to decrease or increase on cooling the gases to 160 K?

Textbook Question

At room temperature, Si is a solid, CCl₄ is a liquid, and Ar is a gas. List these substances in order of (a) increasing intermolecular energy of attraction

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Textbook Question

List the three states of matter in order of (b) increasing intermolecular attraction.

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