Movement paradox?

[Fozzie]

I have read in several articles that "As a substance is heated, the atoms and molecules that make up the substance vibrate faster." Now, Newtons Law of Inertia states that "A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force." So what is causing the vibration?

[toastywombel]

Well the energy being transferred in the form of heat causes the motion, but when you are working on the microscopic level you leave classical mechanics and enter quantum mechanics.

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Furthermore, heat itself is just kinetic energy being caused by the vibration of the molecules and atoms. As they vibrate they bump into molecules and atoms next to them causing them to vibrate. Which also leads to expansion, which is why all substances expand when they are heated.

Edited October 28, 2009 by toastywombel

[insane_alien]

the molecules are jiggling about in random directions, the forces that cause them to change direction are intermolecular/interatomic forces holding the substance together.

 

as the direction at any given time is random, the sum of the velocities is zero.

 

if you heat it up, they move faster, if you cool it down the move slower. the movement of the particles is the very definition of temperature.

[toastywombel]

the molecules are jiggling about in random directions, the forces that cause them to change direction are intermolecular/interatomic forces holding the substance together.

 

as the direction at any given time is random, the sum of the velocities is zero.

 

if you heat it up, they move faster, if you cool it down the move slower. the movement of the particles is the very definition of temperature.

 

Man you always gotta 1-up my explanations iNow. Lol but good to mention that the sum of the velocities is zero, very key.

[insane_alien]

ahem, read my username again.

[toastywombel]

Oooooh, my bad lol Insane_Alien. Either way good point

[iNow]

lol Insane_Alien. Either way good point

 

Thanks!

 

Errm... Oh, wait. Never mind.

[swansont]

Furthermore, heat itself is just kinetic energy being caused by the vibration of the molecules and atoms. As they vibrate they bump into molecules and atoms next to them causing them to vibrate. Which also leads to expansion, which is why all substances expand when they are heated.

 

What you are describing is thermal energy. Heat, technically, is a transfer of energy, but this is high on the list of oft-misused terms in physics. If you heat something up, you will cause vibrations to increase, but the mechanism of heating may not involve atoms at all, e.g. in a microwave oven.

 

Also: there are substance which contract upon heating.

http://en.wikipedia.org/wiki/Negative_thermal_expansion#Materials