### Density of an Object

Objective:  Determine the density of a solid object using the water displacement method.

Example of practical application:  Many medicines are "suspensions" of a crushed solid that is the same density as the liquid it is "suspended" in, allowing the medicine to remain mixed together instead of separating into layers. If the solid and liquid were able to separate, there's no telling what you'd get in your spoonful of medicine.

Important facts: Liquid volumes are measured in (milli)liters, and therefore recorded in milliliters. However, solid volumes are recorded in cubic (centi)meters (Remember volume = length x width x height?) But what if the object doesn't have square sides for you to measure length, width, and height?

Do you happen to have a cube that measures exactly one centimeter for length, width, and height? If so, drop it in a graduated cylinder of water and see how much it raises the water line. Make sure every bit of the cube is under the water line. What? Did you say the water went up exactly one milliliter? Is that a fact? Yes, it is. We know it's a fact because it happens every single time somebody does that, no matter what the object is made out of! After a gazillion times, we now know that

1 mL = 1 cm3

Also, medical personnel often use "cc" to mean cubic centimeters. You might see this on your medicine spoon. Therefore,

1 mL = 1 cm3 = 1 cc

Materials
Electronic scale
4 Objects that fit inside the graduated cylinder

Procedure

1. Record the formula for density. If you don't know it by heart, look it up so your brain will have a better chance of remembering it.
2. Prepare a data table in this format:
 Object Mass (g) Volume 1 (mL) Volume 2 (mL) Volume of object (mL) Volume of object (cm3) Density of object (g/cm3)
3. Write a name for each object in the first column of the table.
4. Record the mass of the first object. Be sure to zero the scale every time you use it.
5. Record the volume of the object using the water displacement method as follows:
1. Fill the graduated cylinder with enough water to completely cover your object. Any volume is fine as long as it falls within the measurement lines.
2. Record the volume of water alone from eye level at the bottom of the meniscus. This is Volume 1.
3. Submerge the object completely under water in the graduated cylinder and record the new water level as Volume 2.
4. Record the volume of the object as the difference between the two volumes.
5. Record the volume of the object converted to cm3, since it represents a solid.
6. Calculate the density of the object using the density formula. Record it in the table.
7. Repeat procedure for the remaining objects for practice.
8. Clean up lab station for Algebra Practice.

Algebra Practice

For each object:

1. Calculate the mass of the object if it occupied a volume of 23.0 mL.
2. Convert that mass from g to kg.
3. Calculate the volume that would be occupied by 150.0 g of this same material.