a. the atoms and molecules of a substance are always in motion
b. the higher the temperature of a substance, the faster its particles move
c. more massive particles move more slowly than less massive particles.
these are the main points of kinetic theory of matter.
Kinetic Theory of Matter
The kinetic theory of matter states that all matter is made of small particles that are in random motion and that have space between them. This means that no matter what phase matter is in, it is made of separate, moving particles.
This theory sounds pretty simple, but it actually explains a lot about the physical properties of matter and how it behaves. You might be surprised to learn that the particles of a solid are actually moving, just not enough for you to see. This type of vibrational movement is why a solid won't change shape no matter what kind of container you put it in.
Remember how liquid particles have more energy than solids? The extra energy in this state allows the particles to move around more freely, and they spread out more than those of a solid, putting more space between those particles. This is why a liquid will take the shape of its container up to its surface.
And since gases have even more energy than liquids, their particles are moving around a lot more, too. This is why a gas will expand to fill its entire container, not just to its surface like a liquid. Not only do the particles of a solid not move very much, but they're also held very close to each other by strong attractive forces. These forces are what hold the particles in place and are what give a solid its fixed size and shape.
On the other hand, the particles of a gas are so far apart that the attractive forces between them are assumed to be negligible. The particles of a gas are viewed as independent from each other, meaning that the gas is the opposite of a solid and has neither a fixed size nor shape.
Since the movement of liquid particles is in between a solid and a gas, the attractive forces between its particles are also in a middle range of the other two phases. Liquid particles have more freedom than solid particles, which is why a liquid can flow freely. This means that like a gas, a liquid has no fixed shape. But because the particles aren't quite as free as those of a gas, a liquid does have a fixed volume.
thanks for asking