Density

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