Solids

• they retain their volume and are incompressible
  • when strong enough force is applied to them, they undergo deformation
• their particles are rather close to one another and act on themselves via rather strong interactions

Amorphous solids

• they don’t have a crysalline latice
• the particles can move around rather freely, but not as freely as to allow free flow
• they are malleble but also fragile
• melting point cannot be easily measured, since the increase in flow is constant

Glass

• glass is a specific form of amorphous solids
• it is mostly amorphous but also contains parts of crystalline strcutred molecules

Crystalline solids

• they have a crystalline latice
• the particles are clearly ordered
• they tend to be rather strong but brittle

Quasicrystalline solids

• these solids seem to have some repeating patterns in their structure, but no in the entire solid
• they commonly have fractal paterns

Molecular solids

• they are made of molecules interacting together only via intermolecular forces
• they are very soft and have low melting points
• they can be either amorphous or crystalline

Covalent solids

• the individual particles are held together via covalent bonds
• they are very hard, have high melting points
• they are generally bad conductors
  • it can be changed by introducing an impurity
• they can be either amorphous or crystalline
• all of these solids can be combined together

Liquids

• the froces between the particles are still rather strong, but they do not prevent spontanious flow
• they are incompressable and don’t expand spontaniously
• particles can flow through the whole volume of the substance rather freely, hence phenomena like diffusion are rather easy to see by naked eye

Gasses

• the forces between the particles are very small to non-existant
• they do not have a fixed volume and are easily compressable
• the movement of particles is practically free, hence phenomena like diffusion are extremely fast

Properties of fluids

• fluids is the collective name for substances which are able to flow, liquids and gasses
• density $\rho$ describes the mass of a certain volume

$$\rho=\cfrac{m}{V}$$

• viscosity describes the inability of a material to flow
• surface tension is the tendency of surfaces to assume the minimum possible area
  • the particles of the material close to the surface do not experience any force per se, but rather are a result of all the forces in the material together
  • the molecules around a liquid have different energies and affect the shape of the surface
    • the resulting shape can be ither flat, concave ($\cup$) or convex ($\cap$)
    • the energy of the whole system is minimal and close to zero still
  • in some cases the liquid flows up or down as the result of it being either attracted to or repulsed from the surface of a container
    • this phenomenon is called capillary acition (either elevation or depression) and it forms either a concave or a convex meniscus