Glass Fragment Notes

Descriptive Properties

· A physical property describes a substance without reference to any other substance.

· weight
· volume
· color
· boiling point
· melting point

· A chemical property describes the behavior of a substance when it reacts or combines with another substance.

Why is glass important to a crime scene?

· It can be lodged in a suspects shoes or clothes.
· Headlight glass can help identify a suspect's vehicle

What is glass made of and how is it made?

· Glass is made of silicon oxide and metal oxides
· Sand and metal oxides are melted and then cooled

Types of Glass

· Window and bottle glass are made of soda-lime, sand, and the following metal oxides: sodium, calcium, magnesium, and aluminum.

· Auto headlights and heat-resistant glass also have boron oxide.

· Tempered glass is stressed glass that is rapidly heated and cooled.

· Laminated glass is used as windshields and is made by sandwiching a piece of plastic between two pieces of window glass

How is a glass fragment analyzed?

· pieces are put together like a puzzle

· refractive index: velocity of light in a vacuum divided by the velocity of light in the medium
· density: the mass divided by the volume