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