You mix two clear liquids and a colored solid forms at the bottom of the beaker. do you think this is a chemical change? how can you know for certain?

The answer is yes. A chemical change occurred.
Chemical change is defined as the rearrangement or alteration in the of atoms in one or more substance which result in the formation of a new substance.

In the above, you mixed two clear liquids and the result was a new substance which is a colored solid precipitate at the bottom of the beaker.
This means that changes in the atoms of the two clear liquids occurred leading to the formation of this new solid substance.

This means that chemical change has occurred.

Hope this helps :)

Particle exchange energy though elastic collision , hope this .