School-college Physics Notes: Thermal energy 5.6 Density
Density & particle theory: 5.6 Density and the kinetic particle model - theoretically explaining relative densities of gases, liquids & solids
Doc Brown's Physics exam study revision notes
and the particle model - explaining the relative densities of gases, liquids and solids
Applying the particle model to the different densities of the states of matter
GASES: The particles have kinetic energy and can move around at random quite freely.
This enables the particles to spread out and fill all the available space giving a material a very low density compared to liquids and solids.
With very weak intermolecular forces (NOT chemical bonds) of attraction between the particles there is no constraint on their movement - they can't club together to form a liquid or solid.
LIQUIDS: In liquids, the particles are close together, usually giving high densities a bit less than the solid, but have a much greater than the density of gases, but the particles are NOT in a fixed close packed ordered state as in solids..
The inter-molecular forces between liquid particles are much greater than those between gaseous particles and are strong enough, so they are attracted close together, with enough kinetic energy to just leave a little free space.
The random movement creates a little free space and on average are spaced out just that little bit more than in solids, hence their slightly lower density than the solid - water is a very rare exception to this rule.
SOLIDS: The strongest interparticle forces of attraction occur in solids where particles are attracted and compacted as much as is possible.
The particles are packed tightly together in an ordered array - giving maximum density.
In small molecules - covalent compounds it is intermolecular bonding, strong covalent bonds in giant covalent structures. Metals have strong chemical bonds between the atoms and similar very strong bonds between ions in ionic compounds.
The particles can only vibrate around fixed positions in the structure and do not have sufficient kinetic energy to overcome the binding forces and break free and move around creating a little space as in liquids.
The result is the highest density for the state of a specific material.
Although liquid densities for a specific material are just a bit less than those of the solid, both the solid and liquid states have much greater densities than the gaseous or vapour state.
Keywords, phrases and learning objectives for density
Using kinetic particle theory model to explain the relative densities of gases, liquids and solids
BIG website, using the [SEARCH BOX] below, maybe quicker than navigating the many sub-indexes
Basic Science Quizzes for UK KS3 science students aged ~12-14, ~US grades 6-8
Advanced Level Chemistry for pre-university age ~16-18 ~US grades 11-12, K12 Honors
Use your mobile phone in 'landscape' mode?SITEMAP Website content © Dr Phil Brown 2000+. All copyrights reserved on Doc Brown's physics revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted. Exam revision summaries and references to GCSE science course specifications are unofficial.
Using SEARCH some initial results may be ad links you can ignore - look for docbrown
ENTER specific physics words or courses e.g. topic, module, exam board, formula, concept, equation, 'phrase', homework question! anything of physics interest! This is a very comprehensive Google generated search of my website
TOP OF PAGE