CBSE Class 9 Answered
Sound travels due to the vibrations caused by the molecules of the medium that carry sound waves from one molecule to the other and so on.
In solids the molecules are tightly packed, that is, the distance between the molecules is very small. So, it takes less time for the moecules of the solids to carry the sound waves from the one molecule to the neighbouring molecule. The molecules in gases are very far apart as compared to solids and liquids, that is, they are the least dense. Hence sound travels slowest through gases. Whereas, the speed of sound depends on the temperature of the medium of propagation and increases as the temperature increases.
For example: When solid (ice) is heated, the temperature decreases hence the speed of sound decreases. When further heated the temperature decreases (liquid gets converted into gas) and the speed of sound increases.