Learning Objectives

• I can draw particulate-level models to illustrate the differences between solid, liquid and gas phases.

• I can explain how gases differ from liquids and solids in terms of spaces between particles and their motion.

Essential knowledge

Particulate Diagrams:

Particulate diagrams or drawing can be used to show how molecules are arranged in the solid. liquid and the gas phase.

Solids:

• Particles can not move freely since they don't have enough kinetic energy and therefore solid particles can only vibrate.

• Particles are held together in place by intermolecular forces resulting in a rigid structure, definite shape and volume.

• Solids are can not be compressed due to the minimum spaces between their particles.

• Crystalline solids have a repeating 3 dimensional structure.

• Amorphous solids have particles that are disordered.

Liquids:

• Particles are still close together, however the molecules have gained enough kinetic energy for them to slide and roll around and that's the main reason why liquids take the shape of their container.

• liquids are close together and because of that they are not compressible.

• The temperature range where the substance is liquid depends on the IMFs in that substance and that includes Hydrogen bonding, dipole-dipole and London Dispersion forces.

Gases:

• Particles have gained enough kinetic energy to overcome the intermolecular forces that hold them together.

• Particles are far apart and moving quickly.

• Because particles are far apart, gases are compressible.

• Gases have indefinite shapes and volume because particles are not regularly arranged.

• Gas particles are in continuous motion. The frequency and the strength of collisions between the gas particles and the container depernd on pressure, temperature and volume.

Check your understanding