Is ice, wood, soil, or air homogeneous?

Homogeneous mixtures are uniform or consistent in their phase and composition. In a homogeneous mixture, the elements forming the mixture do not remain physically distinct. On the other hand, heterogeneous mixtures are not uniform or consistent in their phase and/ or composition. The elements forming the mixture remain physically distinct. A mixture of oil and water is heterogeneous because the two don’t mix, and the elements remain distinct.
Ice is heterogeneous because it is characterized by the solid and liquid phases.
Wood is considered heterogeneous because it is characterized by differences in its grains. A piece of wood exhibits different properties in different parts with regards to toughness, color, and texture.
Soil is also considered heterogeneous because it is made up of different types of matter (plant matter and grit).
Air is homogeneous because its elements cannot be visibly distinguished.
http://chemistry.elmhurst.edu/vchembook/106Amixture.html