What is a characteristic of a gas?

Gases have three characteristic properties: 1. they are easy to compress, 2. they expand to fill their containers, and 3.they occupy far more space than the liquids or solids from which they form. Compressibility. An internal combustion engine provides a good example of the ease with which gases can be compressed.

Explanation:

Gases consist of particles in constant, random motion. They continue in a straight line until they collide with something—usually each other or the walls of their container.

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absorption lines are where light has been absorbed by the atom thus you see a dip in the spectrum whereas.

emission spectra have spikes in the spectra due to atoms releasing photons at those wavelengths.

explanation:

15.3 cos 65 degrees trig