Insulator or Conductor?

As I conducted my experiment of what would be a better insulator.  The materials that I tested

was foil, cotton wash cloth, paper towel and multi-purpose sealing wrap (plastic wrap).  The

reason why I chose these materials is I knew plastic is a good insulator, where metal or foil

would be better  thermal conductors, because heat passes through them quickly.  Material like

plastic, cotton are good thermal insulators because heat does not pass through.  I found that the

plastic wrap and the foil kept the water hotter.  I was a little surprised about the foil, I realized

that the reason for this is that the foil kept that temperature longer.  I did a similar experiment

with my students.I discussed with my students what are good heat conductors, they came up with

metal because heat passes through metal quickly, which allows the heat to go through to heat up

the food. As with wood and plastic (good insulator) that traps heat and keeps things hot. To

reinforce this concept, I took a cup of coffee and ask my students what cup is a better insulator

and a better conductor, a ceramic cup, paper cup or a styrophone?  After the students discussed

this, I had them complete the experiment.  The following results before the experiment out of 16

students:  10 ceramic, 4 styrophone and 2 papers.  After the experiment the students realized that

though ceramic is a good conductor it is a poor insulator because the heated molecules from the

water transferred to the cup making the cup hot, cooling the water.  The paper cup did not keep

the water hot nor did the cup make a good conductor.  They realize that the best cup for an

insulator is the Styrofoam cup. A polystyrene cup keeps the heat in and keeps the coffee hot.