Density • Density is the mass of a given object over a unit of volume • Density is an intensive property • The formula to solve for density is D=m/V
D=m/V • m is mass • Mass should always be in grams (g) • If it is not in grams you must convert to grams • V is volume • Volume of a solid or a liquid can be in mL or cm3 • 1 mL = 1 cm3 • cc is used in medicine for centimeters cubed • Volume of a gas will always be in liters (L)
Volume • Volume of a liquid can be found using a graduated cylinder. • Volume of a gas is the volume of the container it is stored in. • Volume of a solid can be found two ways. • For a geometric shape you can measure the sides in cm and calculate the volume using a formula • For irregular shapes you can use displacement
Volume • Formulas for volume: • Box/cube: V = l x w x h • Cylinder: V= πr2h • If you have the following box and all the measurements are in cm, what is it’s volume?
Volume • If you have the following cylinder, what is it’s volume? • If you are given a volume in something other then cm3 or mL, or L for a gas, you must convert it.
Converting Units That Have a Power • Convert 12.5 in3 in to cm3: • Convert 1.5 ft3 into cm3: • Convert 4.35 cm3 into mL:
Water Displacement Method • Displacement is when you measure the volume of a liquid with out the object in it and the height with an object in it. The difference is the volume of the object.
Density • The density of a solid or liquid will be in g/mL or g/cm3. • The density of a gas will be in g/L. • If you know any two parts of the density formula you can solve for the third.
Density Problems • If you have an object where the volume is 6.52 mL and the mass is 15.21 g, what is it’s density? • If you have a piece of lead, and you know lead has a density of 11.4 g/mL, what would be it’s volume if the it has a mass of 25.45 g?
Density Problems • You have an object that has a mass of 2.1 lbs, and you put the object in a cylinder of water and the water raises from 2.51 gal to 5.45 gal. What is the density of that object? • You know the density of Helium is 0.1785 g/L. And you have helium in a 2.0 L container. What is the mass of the helium in the container?
Comparing Densities • You can compare densities to determine if and object can float on a liquid: • The density of vegetable oil is 0.894 g/mL, will the following objects float in vegetable oil? • Lead 11.4 g/mL • Cork 0.193 g/mL