Pure Substance Contains Only One Kind of Particle

3.9 Model of Matter: The Particle Theory

Particle Theory: 1. All matter is made up of tiny particles 2. All particles of one substance are the same. Different substances are made up of different particles. 3. The particles are always moving. The more energy the particles have, the faster they move. 4. There are attractive forces between the particles. These forces are stronger when the particles are closer together.

Scientists now call the particles in the particle theory atoms.

Pure Substance ~ Contains only one kind of particle.

Elements: Pure substances that cannot be broken down into simpler substances (ie. carbon (C) , Nitrogen (N). Helium (He) ) Each element is made of only one type of atom.

Compounds: Pure substances that contain two or more different elements formed from a chemical reaction. ( ie. H2O, NaCl).

Molecules:. Pure substances where the atoms combining can be the

same or they can be different. (ie. O2, H2O)

Mixture ~ contains at least two different pure substances, or two different types of particles

Homogeneous Mixture( Solution) : Particles mix well with each other, so well that you can only see one phase or visible part. Eg. Salt dissolved in water

Heterogeneous mixture: Particles don’t mix well, you will see more than one phase. Eg. Lucky Charms