【Scatter】 ,  【disperse】 ,  【dissipate】 ,  【dispel】  can mean to cause a group, mass, or assemblage to separate or break up.

【Scatter】 may imply the use or operation of force which drives the persons or things in different directions.

On the other hand,  【scatter】 may imply little more than throwing or casting so that the things thrown will fall by or as if by chance.

【Disperse】  usually implies a wider separation of the units than  【scatter】 and a complete breaking up of the mass or assemblage.

【Dissipate】 suggests definitely the idea of complete disintegration or dissolution (as by evaporation, crumbling, squandering, or blowing away) and consequent vanishing.

【Dispel】 carries less suggestion of separation of units or particles than any of these words but it stresses a driving away as if by scattering of something that clouds, confuses, or bothers.