Sink or Float Lab
Choose whether each object will float or sink, then drop them all into the virtual water tank and see how your predictions match reality. The key is density.
Guided Experiment: Predict and Test: Sink or Float
Before testing any objects, write your prediction: which objects do you think will float and which will sink? What property of an object do you think determines whether it floats?
Write your hypothesis in the Lab Report panel, then click Next.
Make Your Predictions
Click Float or Sink for each object to record your prediction.
Cork
Wood Block
Apple
Plastic Bottle
Orange
Ice Cube
Soap Bar
Egg
Aluminum Coin
Rock
Marble
Steel Bolt
Controls
Data Table
(0 rows)| # | Object | Density (g/cm³) | Predicted | Actual | Correct? |
|---|
Reference Guide
What Is Density?
Density is how much mass is packed into a given volume. It is measured in grams per cubic centimeter (g/cm3).
Formula. Density = Mass divided by Volume. A small, heavy object is denser than a large, light one.
Water has a density of 1.0 g/cm3 at room temperature. Objects with density below 1.0 g/cm3 float; objects at or above 1.0 g/cm3 sink.
Example: cork has density 0.24 g/cm3, which is less than water, so it floats. Steel has density 7.8 g/cm3, far greater than water, so it sinks.
Archimedes Principle
Around 250 BCE, the Greek mathematician Archimedes discovered that an object placed in water is pushed upward by a force equal to the weight of the water it displaces.
Buoyant force. Every submerged object experiences an upward push from the water. If that push equals the weight of the object, it floats.
If the object is less dense than water, it displaces its full weight of water before it is fully submerged, so it stops sinking and floats at the surface.
Real-World Examples
Ships. A steel ship floats because its shape traps a large volume of air, making the average density of the whole ship less than 1.0 g/cm3.
Icebergs. Ice (0.92 g/cm3) floats with about 90% below the surface because it is just slightly less dense than water.
Submarines. Submarines adjust their buoyancy by filling or emptying ballast tanks with water, changing their average density.
Dead Sea. The extra salt in the Dead Sea raises water density to about 1.24 g/cm3, making it much easier to float.
Investigation Tips
Before testing any objects, write your hypothesis: which objects do you think will float and which will sink? What is your reasoning?
After testing, check the density column in the data table. Find the boundary value that separates all the floaters from all the sinkers.
The egg (1.03 g/cm3) barely sinks. Think about what would happen if you added salt to the water to increase its density above 1.03 g/cm3.
Use the lab report to record your hypothesis, observations, and a conclusion that uses the word density.