Section 10-3: Solids
Objectives:
Describe the motion of particles in solids and the properties of solids according to the
kinetic-molecular theory.
Distinguish between the two types of solids.
Describe the different types of crystal symmetry.
Define crystal structure and unit cell.
A. Properties of Solids and the Kinetic-Molecular Theory
1. solid – a form of matter that has a definite volume and a definite shape
a. particles of a solid are more closely packed than those of a liquid or gas
b. particles in a liquid are not bound together in fixed positions; they move
about constantly
c. solids are more ordered than liquids and are much more ordered than
gases; particles are in relatively fixed positions
2. two types of solids: crystalline solids and amorphous solids
a. crystalline solid – solid that consists of crystals
crystal – substance in which the particles are arranged in an
orderly, geometric, repeating pattern
b. amorphous solid – one in which the particles are arranged randomly
3. Definite Shape and Volume
4. Definite Melting Point
a. melting – physical change of a solid to a liquid by the addition of
energy as heat
b. melting point – temperature at which a solid becomes a liquid; kinetic
energies of the particles within the solid overcome the attractive
forces holding them together
10.3b
c. amorphous solids have no definite melting point; e.g. glass and plastic
d. supercooled liquids - substances that retain certain liquid properties
even at temperatures at which they appear to be solid
5. High Density and Incompressibility
6. Low Rate of Diffusion
B. Crystalline Solids
1. crystalline solids exist either as single crystals or as groups of crystals fused
together
a. crystal structure - total three-dimensional arrangement of particles of a
crystal
b. crystal lattice - arrangement of particles in the crystal represented by a
coordinate system
c. unit cell - smallest portion of a crystal lattice that shows the threedimensional pattern of the entire lattice; Fig. 10, p. 338, bottom left
d. a crystal and its unit cells can have any one of seven types of symmetry;
Fig. 11, p. 339, top
2. binding forces in crystals
a. crystal structures can also be described in terms of the types of particles
in them and the types of chemical bonding between the particles;
Table 1, p. 340, top
b. ionic crystals - ionic crystal structure consists of positive and negative
ions arranged in a regular pattern
10.1c
c. covalent network crystals - covalent network crystals, each atom is
covalently bonded to its nearest neighboring atoms;
Fig. 12, p. 341, top right
d. metallic crystals - metallic crystal structure consists of metal cations
surrounded by a sea of delocalized valence electrons
e. covalent molecular crystals - crystal structure of a covalent molecular
substance consists of covalently bonded molecules held together
by intermolecular forces
C. Amorphous Solids
1. amorphous - comes from the Greek for “without shape”
2. atoms that make up amorphous solids are not arranged in a regular pattern
D. Comparing Cohesion and Adhesion
1. cohesion – force of attraction among particles of the same substance
2. adhesion – force of attraction between different substances; e.g. glass and
water; glass and mercury
3. positive meniscus – a concave shaped meniscus formed when the force of
adhesion is greater than the force of cohesion: glass and water
4. negative meniscus – a convex shaped meniscus formed when the force of
cohesion is greater than the force of adhesion: glass and mercury