State of Matter vs Phase of Matter
In physics, something that has a rest mass can be considered as a matter; it is a substance in the universe. It can be either the smallest particles with mass or the largest stars in the universe. The matter that we are concerned about consisting of only 4.6% of the universe, and the rest of the mass lie in yet undetectable forms.
Like energy, matter also can exist in many forms. These forms are known as states of matter. Within a state of matter, atoms and molecules can take different configurations. These are known as phases.
What is Phase of Matter?
The homogenous part of a heterogeneous system separated by a distinguishable boundary is known as a phase. It generally refers to a volume in space, where all the properties of the matter are uniform and physical properties are distinct.
For example, consider the inside of a water kettle when water is boiling. Water (the liquid) occupies the bottom area of the kettle, and separated by the walls of the kettle and upper water surface. And throughout this region the chemical and physical properties are uniform. Just above the water surface, the area is filled with steam and air mixture. In this region too, the walls of the kettle and the water surface creates a distinguishable boundary, and the properties throughout the region can be considered uniform. In this case, boiling water is one phase, and the steam air mixture is one phase. So this system can be considered as a two phase system. Consider water and gasoline poured into a transparent bottle. This is also a two phase system, where the two liquids are clearly separated by a margin.
Investigating the phases of matter is important in determining the physical properties of a substance after transformations. During the processes, phase transitions can occur, and the transitions can be represented by a phase diagram. Phase diagram is a chart that shows how distinct phases can occur in different equilibrium conditions. When the composition of a multi-phase system remains unchanged, it is said to be in phase equilibrium.
What is State of Matter?
The distinct forms the matter in different phases can take are considered as a state of matter. Three classic states of matter are solid, liquid and gas.
In solids and liquids, the intermolecular forces are strong and are considered as condensed states. Solids have the strongest intermolecular forces; therefore, the structure is tightly held together by these forces. Therefore, the shape of a solid is unchanging.
In liquids, the intermolecular forces are relatively weak; therefore, they are moderately held together. And the molecules can slide pass each other, but the forces are strong enough to not to let them escape. In gasses, the intermolecular forces are weak at a level that they are very lightly held together. And they can slide past each other, and completely occupy the volume they are put in.
Matter changes state depending on their internal energy level and the temperature, which is an indicator of the internal energy. At higher temperature, the vibrations in the molecules are strong that they are competing with intermolecular forces to release from the bonds. In solids, internal energy is lower, and when internal energy is increased at a particular level, the bonds get loose, and the solid ice will become liquid. With a further increase in the internal energy / temperature, liquid will transform in to a gas.
Plasma is also considered as a physical state of matter, where the electrons of the gas are stripped, and both electron and nuclei are at very high energy levels. Most of the matter in the universe is in this form; in the vast clouds between stars, called interstellar clouds, and in the stars, where the heat generated turns them into plasma.
Glass and liquid crystals are also considered as separate states in physics. And at very low temperatures, matter form different states as superfluids and Bose-Einstein condensates. In extreme cases, the black holes are also considered as another state of matter, of which we don’t know the exact physical properties.
What is the difference between State of Matter and Phase of Matter?
• A phase is a region with uniform chemical and physical properties and is separated by distinguishable boundaries.
• States of matter are the forms in which different phases can exist. Solid, liquid and gas are the most common states of matter on earth.
• In one state of matter, many forms of phases can exist. For example consider the bottle with gasoline and water. Both are in a liquid state, but in different phases. The same concept can be applied to solids, though the gasses tend to violate this, but not explicitly.