Density is a measurement of how solid something is. Specifically it is the mass per unit volume of a substance.
Density is how much things are packed together.
- It tells you how much stuff (mass) is found in a certain amount of space or volume (D=m/V).
- Imagine a solid cube that is one centimeter tall, one centimeter wide, and one centimeter long. If that cube is filled with Styrofoam, it is light. If it is filled with lead (Pb), it is heavy. The lead is heavier because it has a higher densitythan Styrofoam.
- If you have two objects of the exact same size (volume), the more dense object will weigh more than the less dense object.
- Because all objects are made out of molecules, it is possible to determine how tightly packed those molecules are. This is known as density.
- The more tightly packed the molecules of an object, liquid or gas are, the more dense we say they are.
- The density of a solid object will remain the same no matter where we place the object.
- The density of a liquid will change only slightly. However, the density of a gas changes drastically.
- A gas will expand to fill whatever space it is provided. Thus, if we take a certain amount of gas out of one container and place it into another container that is twice as large the gas will expand, filling the larger container. We still have the same number of gas molecules, but now, they are filling a much larger area. Thus, the gas is half as dense as it was, or in other words, there is twice as much space between the molecules as there was in the smaller container.
- The mass of the atoms or molecules that makes up the material.
- The volume or amount of space the material takes up. If the molecules or atoms are “packed” in more closely, it will be more dense.
- Example: styrofoam is a low density material. Even a large styrofoam container does not weigh much. The molecules in the styrofoam do not have much mass and there is a lot of space between them.
- A brick, on the other hand, is much more dense. Even a moderate sized brick can be pretty heavy. This is because the molecules which make up the rock have more mass and are packed more closely together.
- A less dense substance will float on a more dense substance.
If each ball has the same mass, which box would weigh more? Why?
We can calculate density using the formula:
Calculate the density for each block.
answer for Block I :
Buoyant Force - Why does a ship float?