It is tempting to think that some materials are always heavier than other materials. For example, someone might say that metal is heavier than air. But it depends on how much of each material there is ...

Density describes how closely packed the particles are in a solid, liquid or gas. in a solid ‐ particles are tightly packed in a regular structure in a liquid ‐ particles are tightly packed but free ...

A planet’s mass and volume are easy to determine. Because planets are nearly spheres, we can calculate volume from our knowledge of a planet’s radius, which we determine by measuring both the planet’s ...