Discuss and define derived units. Determine that derived units consist of 2 base unit measurements and is a combination of both units. Examples would be speed, derived from distance and time. Discuss both solid and liquid volume measurements. Determine that liquid volume measurement is recorded in liters and/or milliliters. Determine that 1 cubic centimeter in solid measurement is equal to 1 ml of liquid measurement. One liter of liquid has a volume of 1000 cubic centimeters which is also 1000 milliliter (ml)/ Introduce density as mass per unit volume. Discuss why equal volumes of different substances can possess different densities.