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Lesson # 10.2 : Behavior of Solids and Liquids 57
Contrast the arrangement of particles in liquids and the arrangement of particles in liquids and
solids.
Describe the factors that affect viscosity.
Explain how the unit cell and crystal lattice are related.
The Nature of Liquids
Liquid particles are also in motion.
Liquid particles are free to slide past one another
Gases and liquids can both FLOW. However, liquid particles are attracted to each other, whereas gases are not
Forces of attraction keep molecules closely packed in a Forces
of attraction keep molecules closely packed in a
fixed volume, but not in a fixed position.
Liquids are much denser than gases because of the stronger intermolecular forces holding the particles together.
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Large amounts of pressure must be applied to compress liquids to very small amounts.
Fluidity is the ability to flow and diffuse; liquids and gases are fluids.
• Increasing the pressure on the surface of a liquid has little effect on the volume of a liquid or a solid
– For that reason, liquids and solids are known as the condensed states of matter
Liquids (Cont.)
Viscosity is a measure of the resistance of a liquid to flow and is determined by the type of intermolecular forces, size and shape of particles, and temperature.
The stronger the intermolecular attractive forces, the higher the viscosity.
Liquids (cont.)
Larger molecules create greater viscosity.
Long chains of molecules result in a higher viscosity.
Increasing the temperature increases viscosity Increasing
the temperature increases viscosity
because the added energy allows the molecules to overcome intermolecular forces and flow more freely.
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Liquids (Cont.)
Surface tension is the energy required to increase the surface area of a liquid by a given amount.
Surfactants are compounds that lower the surface tension of water.
Cohesion is the force of attraction between is the force of attraction between
identical molecules.
Adhesion is the force of attraction between molecules that are different.
Capillary action is the upward movement of liquid into a narrow cylinder, or capillary tube.
Nature of Solids
Solids contain particles with strong attractive intermolecular forces.
Most solids have particles packed against one another in a highly organized pattern
Particles in a solid vibrate in a fixed position. Do not flow, nor take the shape of their container
Are still able to move, unless they would reach absolute
Most solids are more dense and less compressible than liquids. Exception: Ice is not more dense than water.
• When a solid is heated, the particles vibrate more rapidly as the kinetic energy increases
– The organization of particles within the solid breaks down, and eventually the solid melts
The melting point (mp) is the temperature a solid turns to liquid
turns
to liquid
At the melting point, the disruptive vibrations are strong enough to overcome the interactions holding them in a fixed position and the solid turns to a liquid
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The type of bonding that exists between the atoms determines the melting points of crystals
• Generally, most ionic solids have high melting points, due to the relatively strong forces holding them together
– Sodium chloride (an ionic compound) has a melting Sodium chloride (an ionic compound) has a melting
point = 801 oC
• Molecular compounds have relatively low melting points
 Hydrogen chloride (a molecular compound) has a mp = ‐112 oC
• Not
Not all solids melt
all solids melt‐ wood and cane sugar tend to wood and cane sugar tend to
decompose when heated
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Solids (cont.)
Most solid substances are crystalline in structure
Crystalline solids are solids with atoms, ions, or molecules arranged in an orderly, geometric shape.
A unit cell is the smallest arrangement of atoms in a crystal lattice that has the same symmetry as the whole crystal.
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Unit Cells
Solids (Cont.)
Solids (cont.)
Amorphous solids are solids in which the particles are not arranged in a regular, repeating pattern. Amorphous solids form when molten material cools quickly.
quickly
Amorphous solids do not have a fixed melting point but rather melts over a range of temperatures.
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Lesson 10.2
The smallest arrangement of atoms in a crystal that has the same pattern as the crystal is called ____. A. crystal lattice B unit cell B.
unit cell
C. crystalline D. geometric cell 0%
D
0%
C
0%
B
A
0%
The viscosity of a liquid will increase as:
A. particle size decreases B. temperature decreases C. intermolecular forces decrease D. particle size increases 0%
D
0%
C
0%
B
A
0%
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