Density describes how much mass is contained in a certain volume. knowing how far apart molecules are in each state, which best ranks solids, liquids, and gasses from least dense to most dense?
solid < liquid < gas
gas < solid < liquid
gas < liquid < solid
solid < gas < liquid

gas < liquid < solid

Explanation:

As we know that density is defined as ratio of mass and volume of the object.

So here if all the molecules of the given matter is packed very close to each other then it can be said that density is high.

So here we know that solids are packed tightly to each other such that force of attraction between them is good then this is said to be high density while in gases the molecules have weak force between them so the packing of the molecules are not too good.

So here we can say that the correct order of density from least to highest is given as

gas < liquid < solid

gas < liquid < solid

Explanation: The most common situation is described:

Solids have the particles very close to each other, this is the reason they conserve the shape.

Liquids have the particles close to each other, but not as much as a solid, the liquids lose their shape but stay together as a homogeneous mass.

Gases have the particles more spread than in the liquid, this is why gases don't even have a shape or homogeneous mass.

On the other hand, the density is calculated as mass over volume, we also can write this as the number of particles in a determined volume, under this viewpoint, it is easy to expect that the densest will be the solids, then liquids and lastly the gasses.

so the solution is: gas < liquid < solid

Something cool to notice is that this is not always true, for example in the case of water, the solid-state of water (ice) is less dense than the liquid water at low temperatures.