Spiritual Science knows of four states of matter: earth, water, air, and fire or warmth.
By “earth” we mean all that is solid; thus frozen water or ice is included in “earth”.
“Water” is all that is fluid; thus molten iron or metal is also “water.”
Air is all that is gaseous; thus steam would come under the heading of “air.”
According to the view of the Physicist of the present day, fire or warmth is only a state of matter, an extremely rapid vibration of its smallest particles.
But to Spiritual Science warmth is also a substance, one much finer than air. According to Spiritual Science, when a body is heated it absorbs the substance of warmth; when it cools it parts with warmth, the substance of warmth can condense to air, this in its turn can condense to water, and this to earth.
All substances were once present merely as warmth. When the Earth was in the Saturn condition, only warmth existed.
Source: Rudolf Steiner – GA 100 – The Gospel of St. John – Lecture III – Basle, 18 November, 1907