LAW OF DEFINITE/MULTIPLE COMPOSITION!!

Law of definite composition:
                Compounds will have a definite composition
          ex. H2O will be H2O anywhere

               (always have 2 hydrogen and 1 oxygen)

Law of multiple composition:

                When 2 or more compounds with different proportions of the same elements can be made

          ex. CO2 → (×2) C2O4

                carbon           dicarbon               (oxalate)

                dioxide           teraocide                

The Heating/Cooling Curve of a Pure Substance Notes:

First step: solid state at any temperature below its melting popint.  Particles are very closely packed together in an  orderly manner.  Forces between the particles are very strong and can only vibrate at a fixed position.

Second step: As it is heated, heat energy is converted into kinetic energy, kinetic energy increases and the molecules vibrate faster about thier fixed positions and their temperature increases.

Third step: Still solid, melting has begun---solid begins to change into liquid.  Temperature remains the same.

Forth step: It exists in both solid & liquid state.  The temperature remains constant the heat that is supplied to it used to overcome the forces of attraction that hold the particles together.  The constant temperature is called the melting point.  The heat energy that abnsorbed to overcome the intermolecular forces is named as the latent of fusion.

Fifth step: All has completely melted.  Solid has turned into liquid.

Sixth step: It is in liquid state.  As the liquid it is heated, the molecules gain more heat energy and the temperature continues to increase.  The particles move faster and faster because their kinetic energy is increasing.

Seventh step: Exists in liquid state.  Molecules have receieved enough energy to overcome the forces of attraction between the particles in the liquid.  Some of the molecules start to move freely and begin the change into gas.

Eighth step: Exists in both liquid and gaseous states.  Temperature remains unchanged.  Heat energy absorbed is used to overcome the intermolecular forces between the particles of liquid rather than increase the temperature.  The constant temperature is boiling point.

Nineth step: All of the liquid has turned into gas.

Last step: The gas particles continue to absorb more energy and more faster.  The temperature increases as heating continues.

Below is a diagram clealy demonstrating the steps of how solid has been transformed into gas through heat.