An adiabatic expansion involving a piston and cylinder is not necessarily reversible.andrewkirk said:I think that 1 and 3 are both specific types of 2, as both are defined to be adiabatic - which just means thermally isolated.
Type 1 is when a thermally-isolated container is divided into two parts separated by an openable divider, with one part containing gas and the other a vacuum, and the divider is then opened, to allow the gas to expand into the vacuum part.
Type 3 is a more complicated process (explained here) where a gas is forced through a valve or porous plug, and the system where this happens is thermally isolated.
Both 1 and 3 are irreversible processes.
An example of an adiabatic expansion that is neither type 1 or 2 would be where the gas in a cylinder expands by pushing back a piston, while remaining thermally isolated. I think (but am not sure) that that would be a reversible process.
The main difference between physical and chemical expansions is the type of changes that occur. Physical expansions involve changes in the state of matter, such as solid to liquid or gas, without any change in the chemical composition of the substance. Chemical expansions, on the other hand, involve changes in the chemical composition of the substance, resulting in the formation of new substances.
Thermal expansions are caused by changes in temperature, while hydronic expansions are caused by changes in the amount of water present in a substance. Thermal expansions can occur in both solids and liquids, while hydronic expansions are typically seen in liquids and gases.
Elastic expansions refer to changes in the shape or size of a substance that can be reversed when the external force is removed. Plastic expansions, on the other hand, result in permanent changes to the shape or size of a substance, even after the external force is removed.
Isotropic expansions occur uniformly in all directions, while anisotropic expansions occur unequally in different directions. This is due to differences in the physical properties of the substance, such as elasticity, in different directions.
Thermal expansions are caused by changes in temperature, while mechanical expansions are caused by the application of an external force. Mechanical expansions can result in changes in both shape and size, while thermal expansions usually only result in changes in size.