What are gases?
All chemical elements can be found in several different states (phases). One of these phases is the gaseous phase. Apart from gaseous an element can also be solid or liquid. Water is called ice when it is solid, it is wet when it is liquid, and when it is gaseous it exists merely as gas or steam. When temperatures rise, the molecules of a substance part, causing the substance to become gaseous and less visible. This phase change causes air to be invisible. When temperatures fall air molecules are closer together and a substance eventually becomes solid. The temperatures at which each ‘phase-change’ takes place differs for each substance.
