Why in solids, sound travels the fastest and heat slowest?

Dear Student,
​​​​​​Answer to your question is given below:

In solids, sound travels the fastest because the molecules are so close, than can collide very quickly, i.e, it takes less time for a molecule of the solid to strike its neighbouring molecule. Solids are packed together tighter than liquids and gases, hence sound travels fastest in solids. The distances in liquids are shorter than in gases, but longer than in solids.

Conduction is considered the slowest mode of heat transfer as it moves from particle to particle. Only conduction takes place in solids. Heat Travels slower because each molecule has to keep moving to be hot, so it takes a long time for each molecule to get moving and stay moving and get the next molecule to keep moving with it. Hence, heat travels slowest in solids.

Regards,