Here's why:

* Density is a measure of how much mass is packed into a given volume. It's calculated by dividing mass by volume: Density = Mass / Volume

* High Volume: Means the object takes up a lot of space.

* Low Mass: Means the object doesn't weigh very much.

If you have a large object (high volume) that doesn't weigh much (low mass), the ratio of mass to volume will be small, resulting in a low density.

Examples:

* A balloon filled with helium: It has a large volume but a very low mass, making it less dense than air and causing it to float.

* A Styrofoam cup: It's bulky (high volume) but lightweight (low mass), giving it a low density.