Intermolecular Forces vs Thermal Interactions - Practice Questions & MCQ

Thermal Energy
Thermal energy is the energy of a body due to motion or movement of its atoms or molecules. As the temperature increases, thermal energy increases so the kinetic energy of the atoms and molecules also increases. As the movement of particles increases, the molecules move far apart from each other. Thus thermal energy is the measure of the average kinetic energy of the particles of matter and responsible for the movement of particles. This movement of particles is also called thermal motion.

Intermolecular Forces vs Thermal Interactions
Intermolecular forces and thermal energy have an opposite effect on the motion of particles. Intermolecular forces are responsible for keeping the molecules together whereas thermal energy tends to keep the molecules apart and in the state of motion.

The net effect of intermolecular forces and thermal energy decides the state of the matter. 

• Gas
• Liquid 
• Solid 

(i) Intermolecular interactions: Strength of intermolecular interactions is highest in solids, then in liquids and least in gases.

(ii) Thermal Energy: Thermal energy of the gaseous state particles is maximum, then is the thermal energy of liquid particles and least thermal energy is of solid particles. 

The two factors namely, pressure and temperature are the deciding factors during the inter-conversion of a state of a substance. Example for changing a gas to a liquid, although the pressure is increased to increase the intermolecular interactions but the interconversion is not possible unless the thermal energy of the molecule is reduced by lowering the temperature. 

For example, water is a liquid at ordinary temperature. When it is heated to 100⁰C it changes into steam (gas). Whereas, when it is cooled below 0⁰C, it changes into ice (solid).