The particle theory states five different things: 1. All matter is made up of tiny particles. This means that anything and everything has particles in it. No matter how small, no matter how big, no matter how dense, whether it be a solid, liquid, or gas it has particles in it. There are two things which we refer to as particles, and they are atoms and molecules. 2. These particles are always moving because they have energy. This means that all the particles are always active, and the more heated they are, the faster they will move. 3. All particles in a pure substance are identical. Basically, no two different pure substances have the same particles, but all the particles in one pure substance have the same particles. This is because all things taken into consideration, if just one minor thing is off, the particles in the two substances will be different. 4. All particles have space between them. Pretty self-explanatory, all particles have space between them. 5. There are attractive forces between the particles. This means that no matter how far particles are from each other, they will always be attracting with one another. But based on common knowledge, we know that the closer two particles are to each other, the stronger the attraction will be.
The particle theory is applied in everything which has particles in it, and all these rules apply to objects which they are applicable to.