Grade 9 Lesson 3 (Liquids/Solids)

Did you ever
wonder why solids
have a definite
shape and volume?

Solids

Thus, there is
more order in a
solid than in a

liquid. Because of
this order, solids

are not fluid.

• have a definite shape and volume
• Solids contain particles with strong attractive forces.
• Particles in a solid vibrate in a fixed position.

Density of Solids

In general, the particles in a
solid are more closely packed than those in a liquid.

Thus, most solids are more
dense than most liquids.

When the liquid and solid states of a substance coexist, the solid almost sinks in the liquid

Solid cubes of benzene sink in liquid benzene because
solid benzene is more dense than liquid benzene.

Ice cubes and icebergs float because water is less dense as a solid than it is as a liquid.

As

water
freezes,

each H2O

molecule can
form hydrogen
bonds with up to
four neighboring

molecules.

As a result, the
water molecules As a result, the water molecules in ice are less-closely packed together than in liquid water.

One exception to this is water.

WHY?

Types of solids

Amorphous solids

An amorphous solid is one in which the particles are not arranged in a regular, repeating pattern. It does not contain crystals.

Example of an amorphous solid:

Amorphous solids

An amorphous solid is one in which the particles are not arranged in a regular, repeating pattern. It does not contain crystals.

An amorphous solid often forms when a molten material cools too quickly
to allow enough time for crystals to form.crystals to form.

Crystalline solids

A crystalline solid is a solid whose atoms, ions, or molecules are arranged in an orderly, geometric structure.

The locations of particles in

a crystalline solid can be represented as points on a framework called a
CRYSTAL LATTICE.

Crystalline solids

A unit cell is the smallest arrangement of atoms in a crystal lattice that has the same symmetry as the whole crystal.

Crystal shapes differ because
the surfaces, or faces, of unit

cells do not always meet at right

angles, and the edges of the

faces vary in length.

seven categories

of crystals based on shape

DONOT MEMORIZE the UNIT CELLS

Categories of crystalline solids

Crystalline solids can be classified into five categories based on:

1- the types of particles that they contain.

2- how those particles are bonded together.

Categories of crystalline solids

Atomic Solids

Metallic solids

Ionic solids

Molecular

solids

Covalent

network solids

• The only atomic solids are noble gases.
• Their properties reflect the weak dispersion forces between the atoms.

Ar

Categories of Crystalline Solids

Atomic
Solids

Metallic
solids

consist of positive metal ions surrounded by a sea of mobile electrons.

Categories of Crystalline Solids

good conductors of heat and electricity.

Malleable

easily hammered into shapes

Ductile

easily drawn into wires

The mobile electrons make metals:

Metallic
solids

consist of positive metal ions surrounded by a sea of mobile electrons.

Categories of Crystalline Solids

The covalent network

structure of quartz, which
contains silicon, is shown in

Figure below.

Figure 19 The most common

kind of quartz has a

hexagonal crystal structure.

Covalent
network

solids

Atoms such as C and Si, which can form multiple
covalent bonds, can form covalent network solids.

Categories of Crystalline Solids

Carbon forms three types of covalent network solids:

Buckminsterfullerene

An element, such as carbon, that exists in different forms at the same

state—solid, liquid, or gas—is called an allotrope

Categories of Crystalline Solids

Covalent
network

solids

Atoms such as C and Si, which can form multiple
covalent bonds, can form covalent network solids.

Carbon forms three types of covalent network solids:

Categories of Crystalline Solids

Covalent
network

solids

Atoms such as C and Si, which can form multiple
covalent bonds, can form covalent network solids.

Most molecular compounds are not solids at room temperature.

Molecular

solids

In molecular solids, the molecules are held together by different types of intermolecular forces.

Categories of Crystalline Solids

Categories of Crystalline Solids

Molecular

solids

In molecular solids, the molecules are held together by different types of intermolecular forces.

Because they

contain no

ions, molecular
solids are poor
conductors of

heat and
electricity.

Ionic
solids

• It consists of cations and anions.
• Each ion in is surrounded by ions of opposite charge.

Categories of Crystalline Solids

Categories of Crystalline Solids

When ionic crystals are struck, the cations and anions are shifted from their fixed positions. Repulsions between ions of like charge cause the crystal to shatter.

• It consists of cations and anions.
• Each ion in is surrounded by ions of opposite charge.

Ionic
solids

Categories of Crystalline Solids

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