Density and How to Measure It
Density is mass per unit volume, found by weighing and by measuring volume, including displacement for an awkward shape. Particle spacing explains why the same substance has a much lower density as a gas.
What a learner can do afterwards
- Calculates density in kg per cubic metre or g per cubic centimetre and rearranges for mass or volume
- Measures the volume of an irregular solid by displacement and reports its density
- Uses particle spacing to explain the density order of a solid, a liquid and a gas
1 · Read
Density packs mass and volume into one number. Divide mass by volume to get it, in kilograms per cubic metre or grams per cubic centimetre. Flip the link to find mass from density times volume, or volume from mass over density.
Tom measures a strange stone. He weighs it on a balance, then lowers it into a measuring cylinder and reads how far the water level rises. That rise equals the volume of the stone. He divides mass by that volume and compares the answer with known values.
Particles explain the usual order of densities. Solids pack tightly, liquids sit looser, and gas particles fly far apart with mostly empty space. The same particles with wider spacing always mean lower density. Floating is a density contest, since denser fluids push harder on what they hold.
Two objects can share a mass yet differ wildly in density if their volumes differ. Always divide before you judge. A big light box can hold the same mass as one small heavy bolt.
Density is mass over volume, and spacing decides its size.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.