The key difference between solutions and mechanical mixtures is that solutions contain dissolved substances whereas mechanical mixtures do not. The components of a solution do not separate when left standing and cannot be separated by filtration.
A solution is a type of mixture. In general, mixtures combine substances that neither bond to one another nor experience chemical reactions. Also, a mixture’s substances can be added without regard to fixed ratios.
A mechanical mixture is non-uniform, meaning that the distribution of each substance throughout the mixture is inconsistent, and its substances remain separate after they are added. Mehanical mixtures are also referred to as heterogeneous mixtures. Salt, sand and water are an example of a mechanical mixture.
Solutions have the same concentration of substances throughout the mixture. Solutions are also referred to as homogenous mixtures. Mixing salt and water without the sand would be an example of a solution, because the salt would dissolve evenly all through the water.
The dissolving substance in a solution is called the solute. The part of the mixture into which the solute dissolves is called the solvent. Usually, there is more solvent in a solution than solute. Most solutions are formed with at least one of their components in a gas or liquid state.