Criminalistics: Chapter 10 - Matter, Light, and Glass Examination

Flashcards covering key definitions, properties, methods, and analysis techniques related to matter, light, and glass examination in forensic science, derived from Chapter 10 of Criminalistics, 13e by Saferstein/Roy.

How do physical properties describe a substance?

Physical properties describe a substance without reference to any other substance, such as weight, volume, color, boiling, and melting point.

What is a chemical property?

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

What is matter?

Matter is anything that has a mass and occupies space.

What is an element?

An element is the simplest substance known and provides the building block from which all matter is composed.

What is a compound?

A compound is a pure substance composed of two or more elements combined.

What is the basic particle of an element?

An atom is the basic particle of an element.

What is the smallest unit of a compound?

A molecule is the smallest unit of a compound.

What are the characteristics of a solid phase of matter?

A solid has a definite shape and volume.

What are the characteristics of a liquid phase of matter?

A liquid has a specific volume and takes the shape of its container.

What are the characteristics of a gas/vapor phase of matter?

A gas or vapor has neither a definite shape nor volume.

What measurement system do scientists primarily use?

Scientists primarily use the metric system of measurement.

What are the basic units of measurement for length, mass, and volume in the metric system?

The basic units are meter for length, gram for mass, and liter for volume.

What is temperature?

Temperature is a measure of heat intensity, or the hotness or coldness of a substance.

How is the Celsius scale derived?

The Celsius scale is derived by assigning the freezing point of water a value of 0°Celsius and its boiling point a value of 100°Celsius.

What is weight?

Weight is the force with which gravity attracts a body.

What is mass?

Mass refers to the amount of matter an object contains independent of gravity.

What is density?

Density is defined as the mass per unit volume.

Why is density considered a characteristic property for identification?

Density is an intensive property, meaning it remains the same regardless of sample size and can aid in identification.

What is refraction?

Refraction is the bending of light waves because of a change in velocity when they penetrate a new medium.

What is refractive index?

Refractive index is the ratio of the velocity of light in a vacuum to that in the medium under examination.

What is double refraction in crystalline solids?

Crystalline solids refract a beam of light into two different light-ray components, resulting in double refraction.

What is birefringence?

Birefringence is the numerical difference between the two refractive indices produced by crystalline solids.

How is glass classified in terms of atomic arrangement?

Glass has a random arrangement of atoms, forming an amorphous or noncrystalline solid.

What are the two models that describe the behavior of light?

Light can be described as a continuous wave or as a stream of discrete energy particles (photons).

When white light passes through a prism, what happens?

When white light passes through a prism, it is dispersed into a continuous spectrum of colors.

What is wavelength?

Wavelength is the distance between two successive crests (or troughs) of a wave.

What is frequency?

Frequency is the number of crests (or troughs) passing any one given point per unit of time.

What are photons?

Photons are discrete particles of light, used to describe electromagnetic radiation once it is absorbed by a substance.

What are the primary components of glass?

Glass is composed of silicon oxides (sand) mixed with various metal oxides like sodium carbonate (soda) and calcium carbonate (lime).

What is float glass?

Float glass is a type of glass, typically used for windows, created when molten glass is cooled on a bath of molten tin.

What is tempered glass?

Tempered glass is a stronger type of glass created by the rapid heating and cooling of its surfaces.

What is laminated glass?

Laminated glass, found in car windshields, has a layer of plastic between two pieces of ordinary window glass.

What two physical properties do forensic scientists evaluate to compare glass fragments?

Forensic scientists evaluate density and refractive index to compare glass fragments.

What is the flotation method used for in glass analysis?

The flotation method is used for precisely and rapidly comparing glass densities by immersing a particle in a liquid until it is suspended.

What is the glass immersion method used for?

The glass immersion method is used to determine a glass fragment's refractive index by immersing it in a liquid whose refractive index is varied until it matches the glass.

What is the Becke line?

The Becke line is a bright halo near the border of a particle immersed in a liquid of a different refractive index, which disappears when the refractive indices match (the match point).

What types of cracks are produced when a projectile penetrates window glass?

The penetration of window glass by a projectile produces radial fractures (radiating outward) and concentric fractures (encircling the hole).

How can a forensic scientist determine the direction of impact on glass?

The direction of impact can be determined by analyzing the radial and concentric fracture patterns in glass, or by applying the 3R Rule.

What is the 3R Rule in glass analysis?

The 3R Rule states that Radial cracks form a Right angle on the Reverse side of the force.

How is the sequence of successive penetrations of glass determined?

The sequence of successive penetrations is determined because a fracture always terminates at an existing line of fracture.

How should glass fragments be packaged for evidence collection?

Glass fragments should be packaged in solid containers to avoid further breakage.