Lesson 3 States of Matter

Objectives- explain kinetic theory and thermal expansion; use kinetic theory to explain the states of matter

All matter is made up of tiny particles called atoms which are always in motion.

This idea is called the kinetic theory of matter. There rate of motion determine whether they are a solid, liquid or gas and some of their properties. The particles that make up solids are moving very slowly. Slow enough that they only have enough energy to vibrate in place. They can not move away form or around other particles.

Figure 1

They stay where they are at. Because of this, solids have definite shape and definite volume.

The particles that make up a liquid have more energy than those that make up a solid. Therefore they are moving more quickly. They have enough energy to move around each other but cannot break free of each other. This ability to move allows liquids to change shape (no definite shape) but they can not change volume-take the shape of the container they are in (definite volume).

Gases have even more energy than do liquids. Particles that make up a gas are moving very fast- in fact oxygen gas molecules at room temperature are traveling approximately 1700km/hr or around 1050mph! When these particles collide with other objects they bounce off great distances away. They are free to move completely away from other molecules. Because of this, particles of gas can change shape and volume (no definite shape or volume).

Plasma is the fourth state of matter. Plasma is not very common on earth. It is found in lightening. The particles in plasma are superheated and are moving extremely fast. When they collide, they have enough speed to break other atoms apart. Plasma makes up the sun and other stars. Since the sun is the biggest object in our solar system, it is the most common state of matter in the solar system.

Special Cases

Sometimes the difference between the states of matter is hard to identify. For example some solids have the ability to flow or change shape for slightly. These are called noncrystalline or amorphous solids. An example of these is silly putty. Some liquids can act like solids. These are called non-newtonian fluids. Examples of this special kind of liquid are cornstarch and water and quick sand.

Thermal Expansion

As matter is heated the particles begin to move more quickly and collide with

each other with more force. As they hit each other harder, they bounce off farther. This

causes the object to become larger. This concept is called thermal expansion. The

opposite is true, that objects contract as they cool. Places where you may of observed

this is the liquid in thermometers and expansion joints in bridges. One important

exception to this rule is water. Water actually expands between 0 and -4 degrees

celsius- or right after it reaches the freezing point. You realize this if you have ever

frozen a can of soda. The can breaks as the water in it expands when freezing.

Questions 8-1

Identify the properties of a solid.

Identify the properties of a liquid.

Identify the properties of a gas.

State the kinetic theory of matter.

What causes the differences between each state of matter?

What is the most common state of matter in the solar system?

Define thermal expansion.

Based upon this section explain why potholes form.

*Explain demonstration #1.

*Explain demonstration #2.