Density of Different States

Dublin Core



In this video we are going to look at what density is, how it is measured and the differences in density between the different states of matter. Informally, density is a measure of how ‘packed’ a material is with mass. Density is defined as the mass of an object per its unit volume. So the big beach ball has a small mass but a big volume, meaning it’s density is low. Whereas the pebble is opposite - lots of mass compacted into a small volume.

Did you know that liquids and gases also have different densities? Look at this density tower of different liquids. The honey is most dense and so sinks to the bottom, whereas milk is in the middle and lamp oil is the least dense. But what about densities between different states? Look at the world around you… think of floating and sinking. When you go to the beach, why does the big beach ball float whereas the small heavy pebble sinks? Why do huge boats float? How come a heavy, wooden log floats on water but a small, lighter paper clip sinks? This is all to do with density!
Air is less dense than water… the beach ball, boat and wooden log are also less dense than water, hence they float. But the pebble and the paper clip are more dense than water, and so sink. Whilst gases are pretty much always the least dense, don’t be fooled into thinking that liquids are always less dense than solids. This just isn’t the case! Density is how heavy an object is for it’s size.
Inside each object are atoms and molecules. How closely these atoms and molecules are packed together and how massive each atom is determines the density. In the rock, the molecules are squished tightly together whereas in wood they are more spread out, and in air much more spread out.
A final thought… think of icebergs - they float on water, so solid ice is less dense than liquid seawater. When the ice melts, so it changes temperature, it becomes more dense and so mixes with the seawater. This means that temperature does affect density. This relationship between temperature and density explains how hot air balloons work… hot air is less dense than the cooler normal air, and so the cooler denser air underneath them pushes the hot air balloons upwards. Hot water is also less dense than cold water, so the top of the ocean is warmer than the bottom. So there we have density. It is a comparison of how heavy an object is compared to it’s size, and also includes the arrangement of atoms inside it.

SUBSCRIBE to the FuseSchool YouTube channel for many more educational videos. Our teachers and animators come together to make fun & easy-to-understand videos in Chemistry, Biology, Physics, Maths & ICT.

VISIT us at, where all of our videos are carefully organised into topics and specific orders, and to see what else we have on offer. Comment, like and share with other learners. You can both ask and answer questions, and teachers will get back to you.

These videos can be used in a flipped classroom model or as a revision aid.

Find all of our Chemistry videos here:

Find all of our Biology videos here:

Find all of our Maths videos here:


Access a deeper Learning Experience in the FuseSchool platform and app:
Follow us:
Friend us:

This Open Educational Resource is free of charge, under a Creative Commons License: Attribution-NonCommercial CC BY-NC ( View License Deed: ). You are allowed to download the video for nonprofit, educational use. If you would like to modify the video, please contact us:

Input by : Elvira Nadya Saleh



FuseSchool - Global Education
published via




Elvira Nadya Saleh


Creative Commons License
This video represents licensed content on YouTube, meaning that the content has been claimed by a YouTube content partner.

Moving Image Item Type Metadata

Imported Thumbnail




“Density of Different States ,” Open Educational Resource (OER) , accessed October 24, 2020,