text: Froth flotation depends on the selective adhesion of air bubbles to mineral surfaces in a mineral/water slurry. The air bubbles attach to more hydrophobic particles, as determined by the interfacial energies between the solid, liquid, and gas phases. This energy is determined by the Young–Dupré equation:
  where:
  * γ is the surface energy of the liquid/vapor interface
  * γ is the surface energy of the solid/vapor interface
  * γ is the surface energy of the solid/liquid interface,
  * θ is the contact angle, the angle formed at the junction between vapor, solid, and liquid phases.
  Minerals targeted for separation may be chemically surface-modified with collectors so that they are more hydrophobic. Collectors are a type of surfactant that increase the natural hydrophobicity of the surface, increasing the separability of the hydrophobic and hydrophilic particles. Collectors either chemically bond via chemisorption to the mineral or adsorb onto the surface via physisorption.