Cryogens are ultra-cold refrigerants used by chemists to remove heat from other substances; common cryogens are liquid nitrogen and liquid helium


            Liquid Nitrogen Ice Cream


Catalysts are substances which speed the formation of products in a chemical reaction but which are themselves not changed



            Preparation of Oxygen Gas from Bleach


Energy of Activation

Energy of activation is the minimal energy which must be present for a chemical reaction to occur



            Reaction of Zinc and Sulfur


Endothermic Reactions

Endothermic reactions are chemical reactions which require heating to cause them to occur


            Formation of a Copper Mirror



Entropy is a measure of the order or disorder of any system;  the greater the entropy the greater the disorder, and vice versa



            Boiling at Reduced Pressure


Exothermic Reactions

Exothermic reactions are chemical reactions which liberate heat energy when they occur


            Genie in a Bottle

            The Thermite Process


Heats of Reactions

Heats of reaction are the various amounts of energy either liberated or absorbed when a change occurs



             Decomposition of Ammonium Dichromate



Photoemission is the emission of light from a substance



            Oxidation of Phosphorus


Relative Stability

Relative stability norms the energy of any substance against the energy of any other substance; the energy of any given substance is said to be relative to that of another substance



            Reaction of Magnesium with Carbon Dioxide

            Oxidation of Phosphorus



Thermodynamics is the branch of science that deals with energy;  in chemistry, thermodynamics deals with energy changes, especially between reactants and products of chemical reactions


            Liquid Nitrogen Ice Cream