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: The '''particle model''' is not a complete explanation for the properties of a [[material]]. However, it is a useful [[approximation]] which can make predictions about the properties of [[solid]]s, [[liquid]]s and [[gas]]es but is not perfect.
: The '''particle model''' only explains the properties of [[solid]]s, [[liquid]]s and [[gas]]es but not why different [[material]]s are [[solid]], [[liquid]] or [[gas]] at different [[temperature]]s.
The problems with the'''particle model''' are that it makes several assumptions which are not always the case:{| class="wikitable"| style="height:20px; width:200px; text-align:center;" |'''Assumption'''| style="height:20px; width:200px; text-align:center;" |'''Reality'''| style="height:20px; width:200px; text-align:center;" |'''Problem'''|-| style="height:20px; width:200px; text-align:center;" |[[Particle]]s are [[sphere]]s.| style="height:20px; width:200px; text-align:center;" |[[Particle]]s are often [[molecule]]s whose shape is not a [[sphere]], some of which are long chains of [[atom]]s.| style="height:20px; width:200px; text-align:center;" |Differently shaped [[particle]]s fit together in different ways which can change the [[property|properties]] of [[solid]]s and [liquid]]s such as the [[strength]] or [[viscosity]].|-| style="height:20px; width:200px; text-align:center;" |There are no [[force]]s between [[particle]]s.| style="height:20px; width:200px; text-align:center;" |[[Intermolecular Force]]s exist between [[molecule]]s.| style="height:20px; width:200px; text-align:center;" |#The strength of the [[Intermolecular Force|intermolecular forces]] affects whether a substance is [[solid]], [[liquid]] or [[gas]] at different [[temperature]]s. The stronger the [[Intermolecular Force|intermolecular forces]] the higher the [[temperature]] of its [[Melting Point|melting point]] and [[Boiling Point|boiling point]].#The direction of the [[Intermolecular Force|intermolecular forces]] affects the way the [[particle]]s are arranged in a [[solid]].|-| style="height:20px; width:200px; text-align:center;" |The size of all [[particle]]s in a [[substance]] is the same.| style="height:20px; width:200px; text-align:center;" |A [[substance]] can be made of more than one different [[particle]] which have different sizes.| style="height:20px; width:200px; text-align:center;" |The different size [[particle]]s causes them to fit together in different arrangements in a [[solid]].|}