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 cm 3 1 mL = 1 cm 3 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= πr 2 h 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 cm 3 or mL, or L for a gas, you must convert it.
Converting Units That Have a Power Convert 12.5 in 3 in to cm 3 : Convert 1.5 ft 3 into cm 3 : Convert 4.35 cm 3 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/cm 3. 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