1. Characteristic Physical Properties

2. Forensic Chemistry Characteristic physical properties are properties that are unique to a substance and can be used to identify it. Unlike height, fingerprints do not change and are specific to the person. They are a characteristic physical property of a person. Intrinsic (Intensive) Properties: Independent of the quantity of matter present. i.e. Density of gold is constant regardless of portion size.

3. Density A measure of how many particles (mass) are packed into a given space (volume). Density is calculated by dividing the mass of a sample by its volume. Where: m = mass of sample V = volume of sample

4. Units of density are usually g/cm 3 for a solid and g/mL for a liquid. The density of a substance is always the same no matter how large it is. 14 karat gold necklace vs. 14 karat gold bar. Eg.1: Calculate the density of a metal sample that is 2.5 cm long, 3.0 cm wide, and 2.5 cm high and has a mass of 196.87 g. What is the identity of the metal? (See Table 1 p.193 for identities).

5. Freezing, Melting & Boiling Points Freezing Point: The temperature at which a liquid changes state to form a solid. It is the same temperature as the melting point of the same substance. 0 o C is the freezing point for pure water. Melting Point: The temperature at which a solid changes state to form a liquid. 0 o C is the melting point for pure ice.

6. Boiling Point: The temperature at which a liquid changes state to form a gas. The temperature at which a substance changes state depends on the particular composition and structure of the substance and is therefore unique to each substance.

7. Applications of Melting Point Metals need to be heated to extremely high temps before they give off a useful amount of light. Most metals melt before they reach these temperatures. Tungsten is the exception, which is why it is used as the filament in incandescent light bulbs. Mercury has a very low melting point (-39 0 C)