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Solids, Liquids, &

Gases (Section 3.1)

Describing The States of Matter

•  Materials can be classified as solids, liquids, or gases based on whether their shapes and volumes are definite or variable

Solid • Set shape and

volume • Particles

tightly packed •  Incompressible

Liquid • Fluid • Constant volume • Shape of container • Particles can move •  Incompressible

Gas •  Shape of container •  Fills the entire volume of

the container •  Particles very far apart •  Compressible

Other States of Matter

•  On earth most matter exists as a solid, liquid, or gas •  But 99% of all matter observed in the universe exists

as plasma, which is not common on earth •  Plasma exists only at extremely high temperatures

such as those found on the sun or other stars •  Bose-Einstein Condensate (BEC) - state of matter that

exist at extremely low temperatures, near -273°C

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Kinetic Theory •  Kinetic energy - energy an object has due to

its motion •  The Kinetic Theory of Matter says that all

particles of matter are in constant motion – According to the theory the particles inside

a solid baseball are moving and the particles in the air the baseball travels through are moving too

Behavior of Gases •  Similar to balls during a game of billiards

–  Ball move in straight lines until it strikes the sides or another ball

–  Transfers kinetic energy •  Gas particles never rest

–  Some move faster than others at average speed –  Collide, slow down, speed up but kinetic energy

of the atoms remains the same •  There are forces of attraction among

particles in all matter –  But for gas particles which are apart and

moving fast the attractions are too weak to have an effect

Kinetic Theory of Gases •  The constant motion of

particles in a gas allows a gas to fill a container of any shape or size 1.  Particles in a gas are in

constant, random motion 2.  The motion of one particle is

unaffected by the motion of other particles unless the particles collide

3.  Forces of attraction among particles in a gas can be ignored under ordinary conditions

Behavior of Liquids •  Have kinetic energy but have a

definite volume because the energy is lower so the atoms move slower than a gas at the same temperature

•  Particles are also closely packed so the attractions between the particles affect the movement

•  A liquid takes the shape of its container because particles in a liquid can flow to new locations

•  The volume of a liquid is constant because forces of attraction keep the particles close together

Behavior of Solids •  Like people sitting in a movie

theater –  Stay in their seats (“fixed”) but

shift and move around in place •  Solids have a definite volume and

shape because particles in a solid vibrate around fixed locations –  Vibration is repetitive back-and-

forth motion •  Strong attractions restrict

movement and keep each atom in a fixed location relative to its neighbors