100. g samples of copper, silver, and aluminum at room temperature are placed on a hot plate.  The initial temperature of each metal is measured and recorded.  The hot plate is turned on.  Which metal will reach 60°C first?  Assume each metal has the same thermal conductivity.

This demonstration is under development.  This web page is under construction.  Web page author: T. Greenbowe, University of Oregon

Curriculum Notes 

Specific heat capacity:    Aluminum 0.91 J/g°C      Copper 0.39 J/g°C      Silver  0.240 J/g°C     Lead 0.160 J/g°C

Assume the hot plate imparts 100 J of energy to each metal every 30 seconds.  An input of  100 J of energy will raise the temperature of 100 g Al by 1.1°C.   An input of 100 J of energy will raise the temperature of silver 4.2°C.  For copper, an input of 100 J will raise the temperature of copper 2.5°C.    The same amount of heat added to 100 g of each metal would give a greater rise in temperature with the metal with the smallest specific heat capacity, if the thermal conductivities of the metals are nearly the same.

Students can use the formula q=c m ∆T  where q= amount of thermal energy transferred, c= specific heat, m= mass of metal and ∆T  is the temperature change. ∆T = q/c m

If 100 J of energy is added to 100 g of aluminum the temperature change for aluminum will be = 100J/(0.91 J/g°C) x 100g = 1.10 °C .  For copper it will be 100/0.39 x 100 = 2.56°C.   For silver 00/0.24 x 100 = 4.6°C.  The smaller the specific heat value, the higher the temperature change, when equal amounts of energy are added to equal amounts of mass of metal.

Thermal conductivity - the ability of a substance to conduct heat (an intensive property of matter).   In general, metals are good conductors are heat.    When a substance is heated (interacts with atoms or molecules having higher energy), the atoms of the metal will gain more energy, and vibrate more. These atoms bump into nearby particles and transfer some of their energy to the particles.  A computer animation of how atoms vibrate more at higher temperatures compare to lower temperatures is available.

Learning Objectives

Discussion 

Specific heat capacity means the amount of heat required to raise the temperature of 1 grams of substance by 1 °C.  If metal A has a high specific heat, and metal B has a low specific heat and the mass of both substances are equal,  more thermal energy will have to be transferred into metal A in order to obtain the same temperature change as metal B.  The metal with the higher specific heat capacity will take longer to achieve the same temperature compare to metal A, if the thermal conductivities of the two metals are nearly equal.

Materials 

two digital thermometers   
100 g sample of lead   
100 g sample of aluminum   
100 g sample of copper  hot plate

two digital displays

Procedure 

In order for students to observe the temperature changing in each metal it is necessary to have two digital temperature probes.  One for each metal.  The temperature probes are connected to a PC or Mac laptop is needed to simultaneously record the temperature of two metals being heated.