Explain each of the following observations using the kinetic molecular theory of matter?

Question

Gases have low desities

The densites of a substance in the solid and liquid states are nearly identical

Answer 1

1. "Gases have low densities"
The kinetic molecular theory makes the following assumptions that are
relevant for this question:

- the static interaction between molecules are negligible.

- the quantum mechanical effects are negligible. This means that the interparticle distance is much larger than the thermal de Broglie wavelength and the molecules can be treated as classical objects

-These molecules are in constant, random motion. The rapidly moving particles constantly collide with each other and with the walls of the container.

Therefore if gas molecules are not bound to each other and are constantly in motion, then they can occupy any container, limited only by the volume of the container. Therefore, since Density = mass/volume, for a given mass of gas, the amount of volume can increase exponentiallly , and it normally does. Therefore, when the volume increases, density decreases.

That is why gases have low densities in general.

2. "The densities of a substance in the solid and liquid states are nearly identical".

That's because their volume doesn't change appreciably when they transitition from one state to another. Density = mass/volume, so if volume doesn't change (since mass is the same), density doesnt' change as well.

The kinetic molecular theory is applicable only for gaseous states, because gases can have variable volume if allowed to expand.

Answer 2

The densities of solids and liquids are nearly identical because even though the molecules are moving faster in the liquid state, they still remain in the same region of the container. The particles are not much farther apart in a liquid than they are in a solid.

The density of a gas is low because as the molecules gain enough energy to break free of the attractive forces between the other molecules, they move as far apart as possible. This means they will move far enough apart to expand and fill the container. A gas takes up about 1000 times more space than either a solid or a liquid.

Answer 3

In both the liquid and solid state the particles are in contact. The hence do not take up very different amounts of space. Imagins a suitcase. You pack tidily to go on holiday (solid). When you return you throw the dirty clothes in anyhow (liquid). They still all go in with a bit of pushing.
Generally solids are slightly more dense than the corresponding liquid. Water is an important exception and the liquid is more dense than the solid. Hence icebergs float. This is because the structure (pattern) in the solid is rather open and has spaces which do not occur when the ice melts.

Answer 4

all of these things are affected and determined by the kinetic molecular theory because they all have to do with the fact that gases are made up of tiny molecules that have perfectly elastic collisions and can be compressed. think of what makes a gas a gas and you can figure these out on your own.