A mixture can be heterogeneous or homogeneous. In a heterogeneous mixture, you can see the different parts. The substances in a homogeneous mixture are so evenly mixed that you cannot see the different parts. A solution is an example of a homogeneous mixture. Air is a solution of nitrogen gas, oxygen gas, plus small amounts of other gases. Unlike compounds, mixtures are easily separated into their components. For example, iron filings can be easily removed from salt with a magnet.