* Homogeneous mixtures have a uniform composition throughout. This means the mixture has the same properties everywhere you sample it.

* Heterogeneous mixtures have a non-uniform composition. You can easily identify different components in the mixture.

In the case of ice cubes in water:

* Ice is a solid form of water with a different density than liquid water.

* Liquid water has a different density than ice.

Because of these differences, you can clearly distinguish between the ice cubes and the water. This makes it a heterogeneous mixture.