Lesson Plan - Get It!
What is heavier, a one-hundred-pound pile of feathers or a one-hundred-pound pile of rocks?
A one-hundred-pound pile of feathers and a one-hundred-pound pile of rocks both weigh the same amount!
Picture a one-hundred-pound bag of feathers in your head. It would be pretty big wouldn't it (and would fill your head)? Feathers weigh less than rocks, so you would need a huge bag of feathers to weigh the same amount as a small group of rocks. Rocks are more dense than feathers.
Density is a word that is used to describe how compact something is based on its size. You will explore density all throughout this lesson.
A great way to remember what density means is to think about a dense population. If you have a dense population of rabbits living in your garden, this means there are many rabbits occupying the same space. A population of one rabbit in your garden is less dense than a population of ten rabbits living in your garden. The population of ten rabbits will take up more space in the garden.
Think about a sailboat. A sailboat is heavy, but it is able to float on water. This is because the weight of the sailboat is dispersed over a large amount of space, and the materials used to make sailboats (such as wood) are generally less dense than water. If you were to build a boat out of bricks, do you think it would float or sink? Tell your parent or teacher.
You're right! A boat made out of bricks would sink, because bricks are more dense than water. There is less air and more compact material in bricks. If you were to build a boat out of wood, the less dense wood would allow the boat to float on the water.
Take a look at another example. If you were to put a sponge and a glass plate into a sink full of water, which one would float, and which one would sink? Tell your parent or teacher.
That's right! The sponge would float and the glass plate would sink. The glass plate has less air and more compact material than the sponge. The sponge has more air inside of it, causing it to float on top of the water. The sponge is less dense than the water, and the glass plate is more dense than the water.
In the Got It? section, you will explore density by completing a floating and sinking activity.