Density & Buoyancy

1. Density & Buoyancy By: Teo Jakobsen Andre Daniel Asher McAlister

2. What Is Density? • Density- The ratio of the mass of a substance to its volume. The greater the mass per given volume, the greater is the density. Lead, for example, has a greater density than aluminum because a given volume of lead weighs more—that is, has a greater mass—than an equal volume of aluminum. The density of a material depends not only on its composition, but also on its temperature. Density is commonly expressed in such units as pounds per cubic foot, grams per cubic centimeter, and grams per liter.

3. How is Density Made Up? • Density is how dense an object is. When the molecules are more packed together inside the object, it gets more dense, and sinks. Objects like metal, stone and brick are some objects that are very dense, and will sink if you put them in water, because their molecules are more tightly packed. If the mass is greater than the volume, it will sink. Molecules in objects that are dense look like this, because their molecules are tightly packed together and that would make this object sink.

4. What is Buoyancy? • Buoyancy- The tendency of an object to rise or float when immersed in a fluid. Any fluid exerts an upward force on an object immersed in it. The strength of the force is equal to the weight of the fluid displaced (pushed aside) by the object; this principle is known as Archimedes' Principle. This principle explains why less effort is required to lift an object submerged in water than to lift the same object when it is out of water.

5. How is Buoyancy Made up? • Buoyancy is how buoyant an object is. If an object is buoyant, that means that the molecules are more spread out in an object. If the volume is greater than the mass, it is more buoyant, causing it to float. Objects like wood, plastic and Styrofoam are a few objects that are buoyant and float. Molecules in buoyant objects look like this. The molecules are spread out, because the object is buoyant. This object would float, because of the molecules being spread out from each other.

6. What is a Suspending Object? • When an object suspends, it does not float or sink, but suspends in between the bottom and the top. When an object suspends, the molecules in the object do not spread apart or pack together. They basically are close enough to go underwater, but far apart enough to not sink to the bottom. When an object suspends, the mass and volume are the same, so one is not greater than the other. An object that would suspend would be a paper substance. When an object suspends, the molecules would look like this. The molecules are not spread out to much, but are not too close together. That means that this object would suspend.

7. 3-D Questions Part 1. • 1. Will the tissue sink, float or suspend? • 2. Will the pencil float, sink, or suspend? • 3. Will the crayon float, sink or suspend?

8. 3-D Questions part 2 • 1. What do you think will happen when we drop the lime and the lemon in the water. Will both sink or float, or will one of them sink while one floats?

9. 3-D Questions part 3 • 1. Will the Aluminum block float, sink or suspend? • 2. Will the Steel float, sink or suspend? • 3. Will the Acrylic block float, sink or suspend? • 4. Will the Poplar float, sink or suspend? • 5. Will the Nylon float, sink or suspend?

10. Questions • 1. If someone rolled up a ball of aluminum, and dropped it in a bucket of water that was 1 foot deep, would it float, suspend or sink? • 2. How does the mass and volume effect an object’s ability to float, sink or suspend? • 3. What causes an object to sink, suspend and float? How does it affect life?

11. Density & Buoyancy Game • http://phet.colorado.edu/sims/density-and-buoyancy/density.swf • This game Works with Density and Buoyancy. Make the block float, sink, and suspend.