TEKS 6.6B: Calculate density to identify an unknown substance. What Is Density? Density is the amount of mass in a certain volume of matter. • • The mass of an object is the measurement of the amount of matter in the object. The SI unit of mass is the kilogram (kg). The gram (g) is a smaller SI unit that is also used to measure mass. 1. Convert Units A bag of apples has a mass of 4.5 kg. What is the bag’s mass in grams? (contd.) TEKS 6.6B: Calculate density to identify an unknown substance. • All matter has mass and takes up space. The amount of space that matter occupies is its volume. • Common units of volume include the liter (L), milliliter (mL), and cubic centimeter (cm3). 2. List What are three different units for expressing volume? (contd.) TEKS 6.6B: Calculate density to identify an unknown substance. • The volumes of solid objects are usually expressed in cubic centimeters. To find the volume of a rectangular solid, multiply its length and width by its thickness. • To find the volume of an irregular solid, submerge the object in water in a graduated cylinder. The water level will rise by an amount equal to the object’s volume in milliliters. 3. Review What are two ways of determining the volume of an object? TEKS 6.6B: Calculate density to identify an unknown substance. How Do You Calculate Density? Density can be expressed as the number of grams in one cubic centimeter. For example, the density of water is “one gram per cubic centimeter (1 g/cm3).” You determine the density of a sample of matter by dividing its mass by its volume. Density = mass/volume 4. Calculate Density An iron meteorite has a mass of 1,875 g and a volume of 250 cm3. What is its density?