Temperature!
Temperature actually is a relative measurement of how fast the particles in a sample are moving/vibrating. Higher-temperature samples have faster-moving molecules (ex: water vapor...the molecules of H2O are moving so fast that they break the intermolecular forces holding them together in liquid water and start flying through the air) and lower-temperature samples have slower-moving molecules (ex: ice ... the molecules of H2O are vibrating slowly and are fairly fixed in position).