Dust particles in the air are an example of a heterogeneous mixture. Here's why:

* Heterogeneous mixtures have components that are not evenly distributed throughout. You can visually distinguish the different parts of the mixture.

* In this case, the dust particles are solid and suspended in the air (a gas). They are not evenly dispersed, and you can see them floating or settling.

Let me know if you'd like more examples of heterogeneous mixtures!