UNIT 3 REVIEW MATERIAL

Properties Physical vs. Chemical

What is a property? A property is an identifying characteristic of a substance. There are two groups of properties that are important to forensic scientists when identifying substances: Physical properties Chemical properties

Chemical Properties A chemical property describes the behavior of a substance when it reacts or combines with another substance. Examples of chemical properties: Wood combining with oxygen in the air to burn or combust Suspect specimen of heroin mixed with Marquis reagentColor change to purple indicates positive result for heroin

Physical Properties A physical property describes a substance without reference to any other substance. Physical properties can be measured without altering a substance’s chemical composition. Physical properties are only associated with the physical existence of the substance Examples of physical properties: Weight, Volume, Color, Boiling Points, and Melting Points

Measuring Physical Properties Temperature Weight Mass Density

Using the metric and English system of measurements Calculations Using the metric and English system of measurements

Measurement System Scientists throughout the world use the metric system of measurement. The metric system has basic units of measurement for length, mass, and volume; they are the meter, gram, and liter, respectively. The following are common prefixes used in the metric system: deci, centi, milli, micro, nano, kilo, and mega.