Chapter 5 Part 1 Notes Organic Analysis Pg

Objectives Define and distinguish elements and compounds Contrast the differences between solid, liquid and gas Describe the usefulness of trace elements for forensic comparison of various types of physical evidence

Vocabulary Matter – anything that has a mass and occupies space Element – the simplest identity of matter 89 occurring naturally Atom – the smallest particle of an element

Vocabulary2 Compound – two or more elements combined which are different both physically and chemically from their elemental components (16 million) 3 states of matter – solid, liquid, gas (vapor) Sublimation – direct change of state in matter from solid to a gas When substances can be distinguished by a visible boundary, different phases exist.

Selecting an Analytical Technique 1. Determine if the substance is: Organic – contain the element carbon commonly combined with hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, bromine Inorganic – compound not based on carbon 2. Decide how the substance will be analyzed Qualitatively – identity of the substance Quantitatively – percent combination of the substances

Organic Evidence Most evidence received at crime labs is organic Commonly abused drugs Synthetic fibers Petroleum products Paint binders High order explosives Most compounds can be identified by the absorption of light = Spectrophotometry Requires a relatively pure state of the material Usually not available

Chromatography Widely used to analyze physical evidence Used to separate and tentatively identify the components of a mixture Basis for observation = chemical substances have a tendency to partially escape into the surrounding environment when dissolved in a liquid or when absorbed on a solid surface Equilibrium = a point where number of molecules leaving a phase will be equal to the number of molecules remaining in phase

Henry ’ s Law When a volatile chemical compound is dissolved in a liquid and is brought to equilibrium with air, there is a fixed ratio between the concentration of the volatile compound in air and the concentration in liquid, and this ratio remains constant at a given temperate

Solubility Distribution or partitioning of a gas between the liquid and gas phases is determined by the solubility of the gas in the liquid The higher the solubility, the greater the tendency of the gas molecules to remain in the liquid phase

Chromatography One phase is continuously moving in one direction over a stationary phase Process is complete when one phase is clearly separated from another

In-Class Assignment 5.1 Review Questions