Glass

Many solids are crystals

A solid in which the atoms are arranged in a regular pattern

Sodium chloride

Glass is an amorphous solid.

A solid in which the atoms are in no order. It is also brittle and shows a conchoidal fracture pattern, has hardness, and elasticity of shape.

Types of Glass

a. Soda-lime glass

most common commercial glass (90% of total production)

least expensive

Composed of:

Sand (silica…SiO2)Soda (Na2O)Lime (CaO)

Soda-lime glass is used for:

b. Borosilicate glass

• strong• heat resistant • contains boron oxides

c. Tempered Glassmade stronger than soda-lime glass by rapid heating and cooling; used for side

and rear windows in cars

Also used in…

Tempered glass breaks into….

d. Laminated glass

For windshields

e. Soda-lead glass

• commonly called crystal or lead glass,

• expensive • widely used for the finest

tableware and art objects.

Comparison

a. Individual evidence (jigsaw fit)

b. Class characteristics1. Flotation

Used to find the density of glass by floating glass particles in liquids of known densities.

Density

Mass per unit of volume

Density = Mass/Volume

2. Immersion method – used to find the Refractive Index of glass

Refractive index (RI)

Formula RI = velocity of light in vacuum velocity of light in medium

The RI of water at room temperature is 1.333

When the Becke line disappears

MATCH POINT The point at which the Becke line disappears

The RI of the glass = RI of the oil

© Hot Stage microscope

Heats the Immersion oil(changes the RI of the oil)

GRIM 2

Annealing

• Slowly heating & cooling of glass

• Makes glass more durable

Data bank

• Densities• Refractive indices• Relative frequencies

in the glass pop of US

Fragmentsa. Types (1) Radial fractures

(2) Concentric fractures

b. First Fractures

• Form on the side of the glass OPPOSITE

the side of the penetrating object

• Radial fractures

c. Next Fracture

• Forms on the SAME side of the glass as the penetrating force

• Forms concentric fractures

d. Stress markings

3 R RuleRadial cracks form a Right angle on the

Reverse side of the force

Fracture Termination

Which bullet hole was made first?

Also know…

Blowback; the backscattering of particles toward the direction of the force.

A high-velocity projectile leaves a wider hole on the exit side of the glass