Chapter #3 – Lecture Notes

The states of matter are the physical forms in which a substance can exist.  The four most familiar states are solids, liquids, gases, and plasma.  All matter is made out of tiny particles called atoms and molecules.  These particles are attracted to each other and are in constant motion.

1)          CRYSTALLINE SOLID – This type of solid has particles that are arranged in a regular repeating 3 dimensional pattern.  Examples are ice and diamonds.

2)          AMORPHOUS SOLID – This type of solid has particles that are not arranged in any particular way.  Examples are rubber and wax.

II)  LIQUIDS - All liquids have a definite volume but not a definite shape.  They take the shape of whatever container they are in.  This occurs because the particles are not as strongly attracted to each other as a solids is, and they are moving faster than a solids.  These particles are further apart than in a solid.  Particle motion in a liquid is called rotational motion.  Liquids have 2 other important properties:

1)      VISCOSITY – This is a liquids resistance to flowing.  Liquids with high viscosities flow slowly, liquids with low viscosities flow freely.  Viscosity changes with temperature.  As temperature increases, viscosity decreases.

III)  GASES - All gases change both shape and volume.  Gases will expand to fill and take the shape of its container.  This occurs because of the behavior of the particles.  A gases particles are the furthest apart and are the least attracted to each other.  The particles are moving the fastest.  Particle motion in a gas is called translational motion.  Gas laws were developed to help explain their behavior.

1)      PRESSURE – The amount of force exerted on a given area.

2)      BOYLES LAW – This law states that for a fixed amount of gas at a constant temperature, the volume of the gas increases as the pressure decreases.  The reverse is also true.

3)      CHARLES LAW – This law states that for a fixed amount of gas at a constant pressure, the volume of the gas increases as the temperature increases.  The reverse is also true.

IV)  PLASMA - This is the state of matter that does not have a definite shape or volume and whose particles are broken apart.  Plasmas conduct an electrical current.  Electrical and magnetic fields affect plasmas.  Examples of natural plasmas are fire, lightning, and the sun (and other stars).  Examples of artificial plasmas are fluorescent lights and a plasma ball.

SECTION #2 – CHANGES OF STATE

A change of state is the conversion of a substance from one physical form to another.  All changes of state are physical changes.  Energy is always involved in any change of state.  When energy is added to a substance the particles move faster.  If energy is removed, the particles slow down.  The temperature of a substance is the measure of the speed of its particles and therefore a measure of its energy.

I) TYPES OF CHANGES

1)      MELTING – This is the change in state from a solid to a liquid, (process). The melting point is the temperature at which this happens.  Melting is an endothermic change, (energy is absorbed).

2)      FREEZING – This is the change in state from a liquid to a solid.  The freezing point is the temperature at which this happens.  Freezing is an exothermic change, (energy is removed).

3)      VAPORIZATION – This is the change of state from a liquid to a gas.  Vaporization is an endothermic change

              a)  BOILING – This is vaporization that occurs 
                   throughout the liquid.  The boiling point is the
                   temperature at which this happens.  Pressure
                   affects the boiling point.

              b)  EVAPORATION – This is vaporization that
                   occurs only at the surface of the liquid.  This
                   happens below the boiling point.

4)      CONDENSATION – This is the change in state from a gas to a liquid.  The condensation point is the temperature at which this happens.  Condensation is an exothermic change.

5)      SUBLIMATION – This is the change in state where a solid goes directly into a gas without first becoming a liquid. Example is dry ice.  This is an endothermic change.

When most substances lose or absorb energy, one of two things happens to the substance, its temperature changes or its state changes.

***REVIEW THE FOLLOWING***

The 3 diagrams on the bottom of page 60.
The chart on the bottom of page 72.
The graph on page 73.
The 2 graphs on the bottom, left, on page 74.  Know that the top one is Charle’s Law, and the bottom one is Boyle’s Law.