Chemistry · Ch 10 — States of Matter
Intermolecular Forces and Thermal Energy
Intermolecular Forces and Thermal Energy
Thermal energy is the kinetic energy that particles of matter possess purely because of their own motion, and it rises directly with temperature -- the hotter a sample, the greater the thermal energy (and hence the speed) of its particles. Which of the three states of matter a substance adopts at a given moment is really the outcome of a tug-of-war between two opposing influences: the intermolecular forces of attraction, which pull particles together and try to hold them in a fixed, ordered arrangement, and the thermal energy of the particles, which drives them apart and keeps them moving. If the intermolecular attraction between a substance's particles is very weak, the particles will not condense into a liquid or freeze into a solid unless their thermal energy is first lowered by cooling. Conversely, to convert a substance from gas to solid, its thermal energy (temperature) has to be reduced enough that the intermolecular forces can finally domina …
What this figure shows. A simple horizontal schematic showing the sequence Solid - Liquid - Gas from left to right, with a label 'Intermolecular Force Increases' pointing back toward solid (intermolecular force is strongest for solid, weakest for gas) and a second label 'Thermal energy decreases' pointing the same direction (the thermal energy/temperature associated with that state is progressively lower going from gas to solid), visually summarising the tug-of-war between intermolecular attraction and thermal energy described i …