Bulk density

Bulk density is how much something weighs when you have a really big amount of it all squished together. It's like when you have a big pile of sand or dirt or rocks. If you just weigh one little scoop of it, that won't tell you how much the whole pile weighs. You have to squish it all together to get the bulk density.

Imagine you have a backpack filled with a bunch of books. A big backpack with a lot of books inside will be really heavy, but one little book won't weigh very much. That's because the books are all squished together in the backpack, and that's how you get the bulk density.

So, if you want to know how heavy a big pile of something is, you need to squish it all together and find out the bulk density. It's a way of measuring how much stuff is in a certain amount of space.