The intramolecular covalent bonds between the hydrogen and oxygen atoms in a water molecule are nearly twenty-five times stronger than the intermolecular bonds between two different water molecules. The intermolecular forces between liquid or solid particles are called van der Waals forces, named after the Dutch physicist Johannes van der Waals who discovered them and explained their major properties. Molecules in a liquid far more easily break their bonds between molecules—bonds resulting from the van der Waals forces—than the much stronger bonds holding the molecules themselves together. That is why each individual molecule in a liquid holds together even though it is repeatedly breaking and reforming bonds with its neighbors. 
Atoms attract other atoms with forces that at first become stronger as two atoms get closer, but then quickly become repulsive when the atoms start to overlap. In a liquid, the thermal energies of the particles is enough to overcome these attractive forces, so the particles can move about each other. In a solid, however, the lower thermal energies of the particles cannot break the attractive force, so the atoms remain in place. But that doesn't mean they don't move! Particles in a solid still have thermal energy that causes them to vibrate. The higher the temperature of the solid, the more energetically the particles are vibrating in place.
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The kinetic energy of a single particle is just equation (3.2) , like the kinetic energy in a baseball. A whole collection of particles can actually have two kinds of kinetic energy: ordered and random. To appreciate the difference, consider a handful of a dozen ping-pong balls. If you throw the whole handful, the group of balls has ordered kinetic energy because there is an average velocity. But suppose you put them in a jar then vigorously shake the jar up and down. The dozen balls will bounce madly around as individuals but the average velocity of the whole group together is zero. Random motion has an average velocity of zero, like the ping-pong balls in a jar. The kinetic energy associated with small-scale random motion of atoms and molecules is what temperature measures. Normal matter has trillions of atoms close together and bumping into each other a trillion times a second. The constant bumping exchanges kinetic energy and keeps the motion truly random.
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Which common phase of matter has the least intermolecular forces?
- Solid
- Liquid
- Gas
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The correct answer is c, gas. In a gas, the molecules are moving so fast that they break the bonds between each other and go flying off. 
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The microscopic thermal motion of atoms is most easily seen in the motion of particles in a 
At lower temperatures, matter is in its