DENSITY
A. What is density?
1. It is one of the ______
2. It is a measurement of how much matter in is a specific space or volume.
3. It helps to think of it as how “crowded” or “crammed” the molecules are in an object.
B. How do you calculate density?
1. Density is mass per unit volume
2. The formula for density is: Density = mass / volume or
3. The units for density are either:
a) grams per milliliter, which is written ______
or
b)grams per cubic centimeter, which is written ______
c)one milliliter is equal to one cubic centimeter
4. Volume is calculate one of two ways:
a) for a regular solid, Volume = ______(this comes out in cm3)
b) for an irregular solid, we use the water displacement technique (this comes out in mL)
C. Density of water
1. The density of water is 1 g/mL
2. Scientists often compare the density of an object to the density of water.
3. If an object has a density less than 1 g/mL, that object will ______in water
4. If an object has a density more than 1 g/mL, that object will ______in water
D. Using Density to calculate mass or volume
1. You can use the MAGIC DENSITY TRIANGLEto help you calculate density, mass or volume.
*Just cover the letter of the unknown, and perform the calculation of the other two amounts*
Let’s try some calculations:
First, let’s calculate the volume of a regular and an irregular shape
Regular shape: While walking on the beach you find a piece of driftwood. You measure the length of the piece of wood to be 29cm. The height of the wood is 22cm and the width is 12cm. What is the volume of this piece of wood? (Remember V= l x w x h)
Irregular shape: While playing outdoors you find a pretty quartz rock. You want to put it in your aquarium, but you don’t want to overflow the aquarium, so you need to calculate how much water to take out of it. You obtain a 250mL beaker and fill it with water until it reaches 150mL. After you put in the quartz rock the water level reads 218mL. What is the volume of the quartz rock?
NOW let’s calculate the density of an object with a regular and an irregular shape
Regular shape: While at the store, you buy a box of cookies. You are curious about the density of the cookies and whether they will float or sink when you dip them in your glass of milk. The mass of the box of cookies is 226.8g. The box measures 20cm x 8cm x 14cm. What is the density? (Hint: you will have to calculate the volume first, before you go on to solve for density)
Irregular shape: You would like to find the density of an unusually shaped piece of jewelry. Since the piece of jewelry has an irregular shape, you need to use displacement to calculate the volume. In a 300mL beaker you pour 200mL of water. When you place the piece of jewelry in the beaker the water level rises to 278mL.
What is the volume of the piece of jewelry?
After computing the volume of the piece of jewelry, you calculate the mass. Upon placing the object on the balance, you find that its mass is 122g. Given this information, calculate the density.