Ch.10 Matter, Light, and Glass

Define physical property and chemical property

A physical property describes a substance's behavior without changing its composition; a chemical property describes how a substance reacts or combines with another substance.

Why is the metric system easier than the English system, and which does the U.S. use

The metric system uses simple powers of ten for conversions; the U.S. uses the English system.

List the basic units of length, mass, and volume in the metric system

Meter, gram, and liter.

What reference points are most often chosen for temperature scales

The melting point of ice and the boiling point of water.

Name the two most commonly used temperature scales and their reference points

Fahrenheit (32° melt, 212° boil) and Celsius (0° melt, 100° boil).

Define weight and mass and explain the difference

Weight depends on mass and gravity; mass is the amount of matter and does not change with location.

Define element and compound and name the smallest unit of each

An element is made of atoms; a compound is made of two or more elements and its smallest unit is a molecule/atom

Name the three states of matter and describe shape/volume for each

Solid (fixed shape and volume), liquid (fixed volume, takes container shape), gas (no fixed shape or volume).

What physical change occurs when going (a) liquid to solid and (b) liquid to gas

(a) Attractive forces increase; (b) attractive forces decrease.

Define sublimation and what happens to molecular forces

solid to gas; molecular/attractive forces decrease.

What is a phase and how can two phases be distinguished

A phase is a uniform piece of matter; different phases have visible boundaries separating them.

how does heat affect density

heating lowers density of liquids and gases.

Define refractive index

the ratio of light speed in vacuum to light speed in a substance.

Difference between crystalline and amorphous solids and how this affects refractive index

Crystalline solids have ordered atoms and two refractive indexes; amorphous solids lack order and have one refractive index.

Explain how a prism disperses white light

Each color has a different frequency and refracts at a different angle, separating the light.

Define intensive property and give two examples

does not depend on size; ex: density and refractive index.

What is color and what determines an opaque object's color

selective absorption of light

opaque objects appear the color they reflect.

What two models explain the nature of light and when each applies

Wave model explains light traveling through space; particle model explains light when absorbed by matter.

List two factors that make comparing glass samples difficult

Glass fragments are often too small or irregular, and most window glass has similar chemical composition.

What is the Becke line and how is it used

A halo around a particle in a liquid of different refractive index; it disappears when the liquid's refractive index matches the glass.

how is the 3R rule applied

helps determine the side of impact.

How to determine the order of successive penetrations in glass

Later fractures terminate at earlier ones; if fracture A ends at B, then B occurred first.

Physical Property

A characteristic describing how a substance behaves without altering its chemical composition.

Chemical Property

A characteristic describing how a substance behaves when it reacts with another substance.

Intensive Physical Property

A property that does not depend on the amount of substance present (e.g., density, temperature, specific heat).

Extensive Physical Property

A property that does depend on the amount of substance present (e.g., mass, volume, pressure).

Metric System

A universal scientific measurement system using the meter, gram, and liter as base units.

SI Units (Système International d'Unités)

The international system of units using standardized base units for fundamental physical quantities.

Temperature

A measure of the hotness or coldness of an object that determines the direction of heat flow.

Density

Mass per unit volume; an intensive property used to characterize substances.

Theory of Light (Wave Model)

Describes light as a continuous wave.

Theory of Light (Particle Model)

Describes light as discrete particles of energy called photons.

Electromagnetic Spectrum

The full range of electromagnetic radiation from cosmic rays to radio waves.

Refractive Index (RI)

The ratio of the velocity of light in a vacuum to the velocity of light in a medium; an intensive identifying property.

Refraction

The bending of light due to a change in speed when passing from one medium to another.

Crystalline Solid

A solid with a definite geometric form due to orderly atomic arrangement.

Double Refraction

A property of crystalline solids that split light into two rays.

Birefringence

The numerical difference between two refractive indexes produced by double refraction.

Amorphous Solid

A solid with a random atomic arrangement (e.g., glass).

Glass

An amorphous solid primarily composed of silicon oxides (sand).

Soda-Lime Glass

Common glass made with sodium carbonate and calcium oxide; does not dissolve in water.

Borosilicate Glass

Heat-resistant glass containing boron (e.g., Pyrex).

Tempered Glass

Strengthened glass created by rapid heating and cooling.

Laminated Glass

Safety glass with a plastic layer between two glass sheets (commonly in windshields).

Flotation Method

A method to compare glass densities by suspending particles in a density-adjusted liquid.

Glass Immersion Method

A technique to determine refractive index by immersing glass in liquids of varying RI.

Becke Line

A bright halo seen around a particle in a liquid with a different refractive index; disappears at the match point.

Match Point

The point where the refractive index of the liquid equals the refractive index of the glass (Becke line disappears).

Radial Fracture

Cracks radiating outward from the point of impact, forming first on the side opposite the force.

Concentric Fracture

Circular fractures encircling the point of impact, forming second on the same side as the force.

3R Rule

"Radial cracks form a Right angle on the Reverse side of the force."

Exit Hole (Glass)

The side of a bullet hole that is wider, indicating the direction the projectile was moving.

Glass Evidence Collection

The process of collecting all glass fragments, packaging them individually, and submitting suspect clothing/shoes wrapped in paper.