Here's a breakdown:
* Density: A measure of how much mass is packed into a given volume. Think of it as how "squished together" the matter is.
* Least dense: This means the substance has the least amount of mass squeezed into a certain amount of space.
Example: A feather is less dense than a rock. This means that a feather takes up more space for the same amount of mass compared to a rock.
Things to remember:
* Density is relative: Something can be less dense than one thing, but denser than another.
* Density is important: It affects how things float, how they behave in liquids, and many other things.
Let me know if you have any more questions about density!