13.3 the nature of solids > 1 copyright © pearson education, inc., or its affiliates. all rights...
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13.3 The Nature of Solids >
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Chapter 13States of Matter
13.1 The Nature of Gases13.2 The Nature of Liquids
13.3 The Nature of Solids
13.4 Changes of State
13.3 The Nature of Solids >
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What is the strongest material in the world?
CHEMISTRY & YOUCHEMISTRY & YOU
It’s not steel or any synthetic plastic, but a form of pure carbon known as fullerene nanotubes.
13.3 The Nature of Solids >
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A Model for Solids
A Model for Solids
How are the structure and properties of solids related?
13.3 The Nature of Solids >
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A Model for Solids
The general properties of solids reflect the orderly arrangement of their particles and the fixed locations of their particles.
13.3 The Nature of Solids >
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A Model for Solids
• In most solids, the atoms, ions, or molecules are packed tightly together.
The general properties of solids reflect the orderly arrangement of their particles and the fixed locations of their particles.
13.3 The Nature of Solids >
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A Model for Solids
• In most solids, the atoms, ions, or molecules are packed tightly together.
• Solids are dense and not easy to compress.
The general properties of solids reflect the orderly arrangement of their particles and the fixed locations of their particles.
13.3 The Nature of Solids >
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A Model for Solids
• In most solids, the atoms, ions, or molecules are packed tightly together.
• Solids are dense and not easy to compress.
• Because the particles in solids tend to vibrate about fixed points, solids do not flow.
The general properties of solids reflect the orderly arrangement of their particles and the fixed locations of their particles.
13.3 The Nature of Solids >
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A Model for Solids
When you heat a solid, its particles vibrate more rapidly as their kinetic energy increases.
• The melting point (mp) is the temperature at which a solid changes into a liquid.
13.3 The Nature of Solids >
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A Model for Solids
When you heat a solid, its particles vibrate more rapidly as their kinetic energy increases.
• The melting point (mp) is the temperature at which a solid changes into a liquid.
– At this temperature, the disruptive vibrations of the particles are strong enough to overcome the attractions that hold them in fixed positions.
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A Model for Solids
The freezing point (fp) is the temperature at which a liquid changes into a solid.
• The melting and freezing points of a substance are at the same temperature.
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A Model for Solids
The freezing point (fp) is the temperature at which a liquid changes into a solid.
• The melting and freezing points of a substance are at the same temperature.
• At that temperature, the liquid and solid phases are in equilibrium.
Solid Liquidmelting
freezing
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A Model for Solids
• In general, ionic solids have high melting points because relatively strong forces hold them together.
– Sodium chloride, an ionic compound, has a rather high melting point of 801°C.
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A Model for Solids
• In general, ionic solids have high melting points because relatively strong forces hold them together.
– Sodium chloride, an ionic compound, has a rather high melting point of 801°C.
• Molecular solids have relatively low melting points.
– Hydrogen chloride, a molecular compound, melts at –112°C.
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Explain why solids do not flow, even though their particles are constantly moving.
13.3 The Nature of Solids >
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Explain why solids do not flow, even though their particles are constantly moving.
In a solid, the particles are packed tightly together and vibrate around fixed points. Even though the particles vibrate, they are limited in their movement and cannot flow.
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Crystal Structure and Unit Cells
Crystal Structure and Unit Cells
What determines the shape of a crystal?
13.3 The Nature of Solids >
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Crystal Structure and Unit Cells
Crystal Structure and Unit Cells
• In a crystal, the particles are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice.
What determines the shape of a crystal?
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Crystal Structure and Unit Cells
The shape of a crystal reflects the arrangement of the particles within the solid.
• In sodium chloride, sodium ions and chloride ions are closely packed in a regular array.
• The ions vibrate about fixed points in the crystal.
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Crystal Structure and Unit Cells
Crystal Systems
Crystals are classified into seven groups, or crystal systems.
a = b = c
a = b = g = 90o
Cubic
a = b ≠ c
a = b = g = 90o
Tetragonal
a ≠ b ≠ c
a = b = g = 90o
Orthorhombic
a ≠ b ≠ c
b = g = 90o ≠ aMonoclinic
a ≠ b ≠ c
a ≠ b ≠ g ≠ 90o
Triclinic
a a a a a a ab b b b b b
c
c
cc c
c
c
b
a = b ≠ c
a = b = 90o, g = 120o
Hexagonal
a = b = c
a = b = g ≠ 90o
Rhombohedral
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Crystal Structure and Unit Cells
Crystal Systems
• The edges are labeled a, b, and c.
• The angles are labeled α, β, and γ.
a = b = c
a = b = g = 90o
Cubic
a = b ≠ c
a = b = g = 90o
Tetragonal
a ≠ b ≠ c
a = b = g = 90o
Orthorhombic
a ≠ b ≠ c
b = g = 90o ≠ aMonoclinic
a ≠ b ≠ c
a ≠ b ≠ g ≠ 90o
Triclinic
a a a a a a ab b b b b b
c
c
cc c
c
c
b
a = b ≠ c
a = b = 90o, g = 120o
Hexagonal
a = b = c
a = b = g ≠ 90o
Rhombohedral
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Crystal Structure and Unit Cells
Crystal Systems
The seven crystal systems differ in terms of the angles between the faces and in the number of edges of equal length on each face.
a = b = c
a = b = g = 90o
Cubic
a = b ≠ c
a = b = g = 90o
Tetragonal
a ≠ b ≠ c
a = b = g = 90o
Orthorhombic
a ≠ b ≠ c
b = g = 90o ≠ aMonoclinic
a ≠ b ≠ c
a ≠ b ≠ g ≠ 90o
Triclinic
a a a a a a ab b b b b b
c
c
cc c
c
c
b
a = b ≠ c
a = b = 90o, g = 120o
Hexagonal
a = b = c
a = b = g ≠ 90o
Rhombohedral
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Crystal Structure and Unit Cells
Crystal Systems
The shape of a crystal depends on the arrangement of particles within it.• The smallest group of particles within a
crystal that retains the geometric shape of the crystal is known as a unit cell.
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Crystal Structure and Unit Cells
Crystal Systems
A crystal lattice is a repeating array of any one of fourteen kinds of unit cells.• Each crystal system can be composed of
from one to four types of unit cells.
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Crystal Structure and Unit Cells
Crystal SystemsThe figure below shows the three kinds of unit cells that can make up a cubic crystal system.
Simple Cubic Body-Centered Face-Centered
In a simple cubic unit cell, atoms or ions are arranged at the corners of an imaginary cube.
In a body-centered cubic unit cell, the atoms or ions are at the corners and in the center of an imaginary cube.
In a face-centered cubic unit cell, there are atoms or ions at the corners and in the center of each face of an imaginary cube.
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Crystal Structure and Unit Cells
Allotropes
Some substances can exist in more than one form.
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Crystal Structure and Unit Cells
Allotropes
Some substances can exist in more than one form.
• Diamond is one crystalline form of carbon.
• A different form of carbon is graphite.
• In 1985, a third crystalline form of carbon was discovered. This form is called buckminsterfullerene.
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Crystal Structure and Unit Cells
Allotropes
In diamond, each carbon atom in the interior of the diamond is strongly bonded to four others. The array is rigid and compact.
In graphite, the carbon atoms are linked in widely spaced layers of hexagonal arrays.
In buckminster-fullerene, 60 carbon atoms form a hollow sphere. The carbons are arranged in penta-gons and hexagons.
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Crystal Structure and Unit Cells
Allotropes
The physical properties of diamond, graphite, and fullerenes are quite different.
• Diamond has a high density and is very hard.
• Graphite has a relatively low density and is soft and slippery.
• The hollow cages in fullerenes give them strength and rigidity.
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Crystal Structure and Unit Cells
Allotropes
Diamond, graphite, and fullerenes are crystalline allotropes of carbon.
• Allotropes are two or more different molecular forms of the same element in the same physical state.
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Crystal Structure and Unit Cells
Allotropes
Diamond, graphite, and fullerenes are crystalline allotropes of carbon.
• Allotropes are two or more different molecular forms of the same element in the same physical state.
• Although allotropes are composed of atoms of the same element, they have different properties because their structures are different.
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Crystal Structure and Unit Cells
Allotropes
Only a few elements have allotropes.
• In addition to carbon, these include phosphorus, sulfur, oxygen (O2 and O3), boron, and antimony.
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What structural properties make fullerene nanotubes the strongest material in the world?
CHEMISTRY & YOUCHEMISTRY & YOU
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What structural properties make fullerene nanotubes the strongest material in the world?
Each carbon atom is covalently bonded to three other carbon atoms. The structure creates a spherical cage or cylindrical tube. This shape allows force to be distributed evenly across the surface so that the entire structure can withstand great force and is extremely strong.
CHEMISTRY & YOUCHEMISTRY & YOU
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Crystal Structure and Unit Cells
Not all solids are crystalline in form; some solids are amorphous.
• An amorphous solid lacks an ordered internal structure.
• Rubber, plastic, and asphalt are amorphous solids.
• Their atoms are randomly arranged.
Non-Crystalline Solids
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Crystal Structure and Unit Cells
Non-Crystalline Solids
Other examples of amorphous solids are glasses.
• A glass is a transparent fusion product of inorganic substances that have cooled to a rigid state without crystallizing.
• Glasses are sometimes called supercooled liquids.
• The irregular internal structures are intermediate between those of a crystalline solid and those of a free-flowing liquid.
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What is the difference between an amorphous solid and a crystalline solid?
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What is the difference between an amorphous solid and a crystalline solid?
Particles in a crystalline solid are arranged in an orderly, repeating pattern or lattice. Particles in an amorphous solid are arranged randomly.
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Key Concepts
The general properties of solids reflect the orderly arrangement and the fixed locations of their particles.
The shape of a crystal reflects the arrangement of the particles within the solid.
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Glossary Terms
• melting point: the temperature at which a substance changes from a solid to a liquid; the melting point of water is 0°C
• freezing point: the temperature at which a liquid changes into a solid
• crystal: a solid in which the atoms, ions, or molecules are arranged in an orderly, repeating, three-dimensional pattern called a crystal lattice
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Glossary Terms
• unit cell: the smallest group of particles within a crystal that retains the geometric shape of the crystal
• allotrope: one of two or more different molecular forms of an element in the same physical state; oxygen (O2) and ozone (O3) are allotropes of the element oxygen
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Glossary Terms
• amorphous solid: describes a solid that lacks an ordered internal structure; denotes a random arrangement of atoms
• glass: a transparent fusion product of inorganic substances that have cooled to a rigid state without crystallizing
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END OF 13.3