Kinds of Matter
Material
Some objects are made of material that seems to have a consistent compositon throughout. This might be a metal, glass, marble, plastic, paper, etc. Such material is referred to as "homogeneous". If the material obviously varies from one region to another, as seen in travertine, wood grains, particle board, are called "heterogeneous". The composition varies throughout a heterogenous material. Rocks can be homogeneous as is the case of fine-gained igneous rocks such as obsidion or heterogeneous as in the coarse-grained igneous rocks such as granite. Clear solutions are homogenous mixtures as is the air.
Substances
A "substance" has a rather definte chemical composition. As such a substance is homogeneous. A salt solution is homogeneous but is not a substance because the chemical composition is quite arbitrary. It can range from very dilute to concentrated and still be a homogeneous material. A substance usually refers to materials such as salt, sugar, water, calcite, quartz, potassium chloride, all of which have definte ratios of their component elements. Nitrogen is a substance, air is not. Zinc or zinc oxide are sustances, bronze and brass are not. Ethanol is a substance, wine is not. Wine can have a wide range of compositions, ethanol contains definite ratios of carbon, hydrogen and oxygen combined in a certain way. A glass of water with ice-cubes is heterogeneous in that there different "phases" that have distinct boundaries and interfaces yet there is a single substance there (water). The ice is a solid phase, the water is a liquid phase.