You might be thinking that I made a mistake in the title. But the reason why I said Plasma in the title was because there are 4 States of matter not 3 so your wrong about saying there are 3 States of matter.
Now lets describe the properties.
Solid: Rigid, Fixed Volume, Can often be cut or shaped
Liquid: Flows, Fixed Volume, Easy to fill up Containers
Gas: Floats, All around us, often invisible
The reason why there are different states of matter is because the different states of matter depend on the distance of the atoms or molecules. If the atoms(/ molecules) were at their final state (plasma) they would be so far apart that the individual particles Photons, Neutrons & Electrons would even separate. Science definitely is very mind Boggling.
What is the smallest particle?:
You might be wondering what is the smallest particle well this answers your question. The smallest known particle which has mass is a particle called Neutrino.
Periodic table:
The Periodic table shows you all of the known elements that our whole world is made up of. On periodic tables they often use abbreviations to tell you the element. On each top left corner on each block there’s a little number which tells you how many Neutrons, Electrons & Photons make up there are to make up the element. So try out the Periodic Table for yourself.
Hyperlinks:
http://www.chem4kids.com/files/matter_intro.html
http://www.bbc.co.uk/bitesize/ks2/science/materials/solids_liquids_gases/play/
The Fun Life of Joe 
Wow, Joe, this is really interesting. If you understand it (as you seem to) you are starting to be a scientist.
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