kinetic theory/energy

explanation of the behavior of molecules in matter; states that all matter is made of constantly moving particles that collide without losing energy.

melting point

temperature at which a solid begins to liquefy.

heat of fusion

amount of energy required to change a substance from the solid phase to the liquid phase.

boiling point

the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on the surface of the liquid.

heat of vaporization

the amount of energy required for the liquid at its boiling point to become a gas.


spreading of particles throughout a given volume until they are uniformly distributed.


matter consisting of negatively and positively charged particles, like on the sun.

thermal expansion

increase in the size of a substance when the temperature is increased.


ability of a fluid - a liquid or a gas - to exert an upward force on an object immersed in the fluid. As in an object that floats.


amount of force exerted per unit area; SI unit is the pascal (Pa)


a fluid's resistance to flow.


a measure of the average kinetic energy of all the particles in an object

amorphous solids

from the greek word for "without form," these solids are like glass or plastic. There is no exact temperature where a phase change occurs due to the lack of structure in the particles.

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