Objective
These experiments are aimed at: a) the determination of the density of an irregularly shaped object from the volume of fluid displaced when it is immersed in a fluid and it's mass when measured on a balance and b) the demonstration of the principles governing fluid behaviour.

Equipment
See the Java and Shockwave applets below. All data and calculations can be recorded using these sheets and your handout.

Definition
The Shockwave applet below shows a simple experiment that tests how well various objects float in water (and other liquids). The basic idea is to grab an object, drag it to the scale, and note its mass. Then, you'll drag this same object to the graduated cylinder to figure out its volume. You'll use its mass and its volume to figure out its Density (recall that the density of a substance is its mass divided by its volume; or, in symbolic terms, D = m/V).

Finally, based on the density of the object, and the density of the fluid, you'll make a guess or hypothesis as to whether or not that object will float in the liquid. You'll then repeat this for various objects and various fluid densities.

Procedure

1. For five of the 10 objects (blue square, blue triangle, red square, red oval, pink square, purple oval, green triangle, grey triangle, tan rectangle, and red/black rectangle):
   1. Use the scale to measure the mass of each object
   2. Use the graduated cylinder to measure the volume of each object
   3. Calculate the density of each object
2. Set the density of the liquid to 1 gm/cc
3. For each object, record your guess (hypothesis) of whether or not it will float in the pail

   STOP! Do NOT put the object(s) in the pail! Record your hypotheses FIRST and show them to your class supervisor before you proceed...

4. Place each object in the pail and confirm/deny your hypothesis
5. For each object, record your guess (hypothesis) of whether or not it would float if the density of the liquid was raised to 2 gm/cc
6. Change the density of the liquid to 2 gm/cc and confirm/deny your hypothesis by placing each object in the pail
7. Using the chart under the Help screen (click the ? to display the help screen), identify the type of each object.

The Shockwave Applet:

URL: http://ippex.pppl.gov/interactive/matter/denslab.html

In this applet, we use mass density (mass/volume) where mass is measured in grams (gm) and volume is measured in cubic centimeters (cc). And so mass density is measured in units of gm/cc.

IF mass is measured in kilograms and volume in cubic meters (SI units), the density would be kg/m³. The conversion is 1gm/cc = 1000kg/m³

Questions

1. Based on what you learned by doing this, what is the relationship between the density of each object and whether or not it floats in the pail? Please record your answer on the fill-in sheet.

Notes

• Some program notes:
  • 1 cc = 1 ml = 1 cm³
  • draught = the depth of a vessel's keel below the surface
  • The object is the same thing as the body
  • Density is D = ^m/_V and the Weight is w = m · g
  • Some of the objects in the first part cannot be identified by their density (they are unknown)
• Be sure to use the correct units for each measurement and calculation!
• Please record your answers on the fill-in sheet.