To begin with, let's say a few words about solids, liquids and gases. They literally stuck together.

This is why solids have a finite shape, such as a ball or cube. But although the molecules are packed very densely, they still vibrate slightly around their middle position (nothing in nature stands still).

Molecules in liquids and gases

In liquids, molecules are connected to each other more freely. They slide and move relative to each other. Therefore, fluids flow and occupy the entire volume of the vessel into which they are poured. In gases, molecules are completely unrelated to each other. They fly at high speeds in all directions.

The average speed of a hydrogen molecule at a temperature of 0 degrees Celsius is 5600 kilometers per hour. Between the gas molecules there is a mass of free space. You can go through the gas cloud and not even notice it.

Why are gases transparent and no solid?

Temperature plays a decisive role in whether a given substance is solid, liquid or gaseous. With normal pressure on the surface of the earth at a temperature of 0 degrees Celsius and below, water is a solid. At temperatures between 0 and 100 degrees Celsius, water is a liquid. At temperatures above 100 degrees Celsius, water is gas. Steam from the pan spreads evenly in the kitchen in all directions.

Based on the foregoing, suppose that through gases it is possible to see, and through solids this is not possible.But some solids, such as glass, are as transparent as air. How is this done? Most solids absorb light incident on them. Part of the absorbed light energy is spent on heating the body. Most of the incident light is reflected. Therefore, we see a solid body, but cannot see through it.

Why is the glass transparent?

Glass molecules absorb the photons of the light incident on it. At the same moment, glass molecules emit the same photons in the same direction. Glass absorbs photons and emits the same photons in the same direction. In this way, the glass is transparent, that is, in fact, it transmits light. The same thing happens with water and other almost colorless liquids. Most of the incident light is carried by molecules. Some photons are absorbed, and their energy is spent on heating the liquid.

In gases, molecules are located at long distances from each other. Rays of light can pass through a gas cloud without encountering a single molecule in its path. This happens with most photons of sunlight passing through the earth's atmosphere. Light in a collision with gas molecules scatters. When white light collides with a molecule, it splits into the color spectrum. Therefore, apparently, the gases of the earth's atmosphere look blue. Despite this, they are considered transparent.