In this series of physics experiments, we learned about temperature and heat transfer.  Many people don't understand the difference between temperature and heat.  Temperature may be defined as the degree of hotness or coldness of a substance.  Heat may be defined as the flow of thermal energy.  Thermal energy is the net disordered kinetic energy of particles in a system.  To learn more about kinetic energy, click here.
 

Electronic Temperature and Sensor and Computer Data Acquisition

    In order to perform our experiments, the temperature probe connected to the computer must be calibrated.  The electronic temperature sensor was calibrated using two standards.  The temperature sensor was placed in a water bath along with a glass thermometer.  The voltage on the probe was allowed to stabilize.  The temperature was then read from the glass thermometer.  The temperature sensor was then placed in a cup of hot water with a glass thermometer.  The voltage was allowed to stabilize and the temperature was read from the glass thermometer.  The temperatures were saved in a file.

Time Delays

    In the next experiment, we used the electronic temperature probe to measure how quickly the probe equilibrates in ice and room temperature.
    The prediction of the time for the electronic probe to reach equilibrium when immersed into an ice bath was about 75 seconds.  The blue line on the graph below shows a quick drop in temperature with an equilibration at 50 seconds.
    The prediction of the time for the electronic probe to reach equilibrium after being removed from the ice water bath was about 100 seconds.  The red line on the graph shown below shows a slow increase in temperature with a temperature equilibrium at 250 seconds.  The reason for the slow increase in temperature was because the air is less dense than the water.  The air is warming the probe.
    The turquoise line represents the temperature as the probe is removed from the ice to room temperature water.  The speed at which the temperature equilibrates is dependent on the density of the material the the probe is in contact with.  Water is less dense than ice, but more dense than air.  Therefore, the temperature equilibrates quicker when going from ice to room temperature water (the turquoise line) than when going from ice to room temperature air (the red line).

Temperatures of Wood, Styrofoam, and Metal

    In the next experiment, the temperatures of three substances (wood, Styrofoam, and metal) were taken.  The substances were first felt by the students.  The metal felt cold.  The wood felt about room temperature.  The Styrofoam was warm.  Next, the actual temperatures of the substances was taken after the temperature probe was calibrated.  The temperature of the metal equilibrated at 27 C.  The temperature of the wood equilibrated at 24.5 C.  The temperature of the Styrofoam equilibrated at 25 C.  The materials were approximately the same in temperature.  Why, then, did the materials feel different to the touch?  The materials felt different temperatures because of the materials of which they are made.  The metal is a conductor and takes heat from our fingers when we touch it.  We are warmer than the metal and it draws our body heat thus creating a “cold” sensation. The wood is of intermediate conductivity and is made of grains all going in the same direction.  The Styrofoam felt warm to the touch because it is made of air and is an insulator.
 

Temperature Change When Mixing

    The next portion of the experiment involved mixing 100 ml of room temperature water with 100 ml of approximately 100 C water.  A diagram of the experiment is shown below.

    The 100 C water was heated with a double boiler as shown in the drawing below.

    It was predicted that when the hot and cold water were mixed, the final temperature would be around 60 C.  The actual temperature was 52 C.

    In the next part of the experiment, 100 mL of room temperature water (20 C) was mixed with 50 mL of hot water (~100 C).  It was predicted that the temperature would equilibrate at 40 C.  When 100 mL of  20 C water was mixed with 50 mL of  96 C, the temperature equilibrated at 43 C.

    In both parts of the experiment, our predictions were close to the original.  The experiments support the conservation of energy theory.  The heat lost by the hot water was gained by the cold substance resulting in an equilibrium temperature.

Hand Cranked Generator and Resistor

    When a hand cranked generator was attached to a 10 Ohm resistance, a warm sensation was felt on my fingers.  The reason for this feeling was because there was 14 Watts of energy with little resistance to the current to keep it from flowing to my fingers.
    However, when a hand cranked generator was attached to a 10,000 Ohm resistor, no sensation was felt on my fingers.  The reason for this lack of feeling was because there was 1,000 times less the flow of energy because there was more resistance.

Heat Pulser

    In the final experiment, water and oil were separately heated using a heat pulser.  The heat pulser apparatus was set up as diagrammed below.

Thanks to Ronnie Sebilo-Tibbits for the drawing above

    The temperature of the water bath and oil as a function of number of joules added was measured and is shown in the graph below.

    The heat capacity for the water and oil was calculated by multiplying the inverse slope and the inverse mass.

    The heat capacity for water was 4,349.52 J/kg*Deg.  The heat capacity for the oil was 2,353.29 J/kg*Deg.

    The specific heat capacities for the two substances are different which is why we see a difference between the two substances when they are heated.  The heat capacity for water is twice as large as the heat capacity for oil.  The value obtained in the lab is similar to the actual heat capacity of water, which is 4,186 J/kg-K.  The percent difference in our experimental heat capacity and the actual heat capacity of water was 3.89%.  Our class was unable to find the actual specific heat capacity for oil, but it was assumed that our value for the specific heat capacity of oil was correct.  On the graph, the line for the specific heat capacity of oil is steeper than the water.