“PYROTECHNIC PENCILS” OBJECTIVE: OBSERVE THE TRANSFORMATION OF ONE FORM OF ENERGY TO ANOTHER FORM, AND HOW ENERGY LOSS RESULTS IN HEAT PRODUCTION.

ELECTRONS WILL FLOW THROUGH CONDUCTORS SUCH AS A WIRE WITH VERY LITTLE RESISTANCE. ELECTRONS FLOW POORLY OR NOT AT ALL THROUGH INSULATORS (NON CONDUCTORS) SUCH AS GLASS OR PLASTIC. SOME SUBSTANCES FALL BETWEEN CONDUCTORS AND INSULATORS AS TO THE EASE WITH WHICH ELECTRONS WILL FLOW THROUGH THEM.

GRAPHITE – AN ALLOTROPE (DIFFERENT FORM, SAME PHASE) OF CARBON – IS A WELL-KNOWN MODEST CONDUCTOR. BECAUSE IT ALLOWS ELECTRONS TO FLOW BUT RESISTS THIS FLOW, GRAPHITE IS COMMONLY USED AS A RESISTOR. IN RESISTORS, SOME OF THE ENERGY OF THE FLOWING ELECTRON IS TRANSFORMED OR LOST AS THERMAL ENERGY (HEAT).

A ROD OF PURE GRAPHITE WILL CONDUCT MORE THAN IT RESISTS ELECTRICITY, SO LITTLE HEAT IS GENERATED. BY ADDING AN INSULATOR SUBSTANCE LIKE CLAY TO THE GRAPHITE, MORE RESISTANCE RESULTS AND MORE HEAT IS GENERATED.

BY A FORTUNATE COINCIDENCE, PENCIL LEAD IS A MIXTURE OF GRAPHITE AND CLAY (THERE IS NO LEAD IN A PENCIL). THE RATIO OF CLAY TO GRAPHITE INCREASES AS THE HARDNESS RATING OF THE PENCIL INCREASES. FOR EXAMPLE, THE NUMBER 2 PENCIL USED ON YOUR SAT TESTS HAS A LOWER CLAY CONTENT THAN A NUMBER 3 OR 4 PENCIL.