The dewar and coffee cup operate equivalently and are interchangeable for performing calorimetric experiments involving metals, salts, ice, and reactions. The dewar and coffee cup calorimeters consist of the insulating vessel itself, the Control Panel, stirrer, thermometer, and the lid. The lid can be moved to the ring stand on the left so materials can be added, filled with water at the sink, or emptied at the disposal bucket. Materials can also be added with the lid on and the lid will move upward momentarily while a sample or solution is added. Clicking on the thermometer opens the Thermometer Window, and clicking on the green and red buttons on the stirrer will turn stirring on and off. The Control Panel is used to control various aspects of the dewar or coffee cup calorimeter. The items that can be controlled include the stirrer, the electrical or calibration heater, the current for the heater, saving data to the lab book, and graphing.
Calibration Heater. The powersupply for the calibration heater inside the dewar and coffee cup is a constant current device, and the slider on the Control Panel is used to set the current between 0 and 500 mA. The lower LCD is used to display the current setting, and the upper LCD is used to display the voltage across the heater. When the voltage or upper LCD reads zero, then the heater is off. The green and red lights on the left of the Control Panel are used to turn the heater on and off. If the Stopwatch Window is open, then the stopwatch will automatically measure the length of time the heater is on. If the liquid level gets too low in the dewar or coffee cup while the heater is on, the heater will burn out disabling the calibration heater until the laboratory is cleared. This will be indicated by a blinking red heater light.
Thermometer. Clicking on the thermometer will turn on the thermometer and open the Thermometer Window in the Live Data tab where the current temperature inside the calorimeter will be displayed. The Save button on the Thermometer Window or on the Control Panel is used to save the temperature as a function of time to the lab book where it can then be copied and pasted into an external spreadsheet program for later analysis. The Graph button on the Temperature Window or on the Control Panel is used to open the Graph Window. Details on the Graph Window are described below. The Units button on the Thermometer Window is used to change the temperature units displayed in the window.
Stirrer and Level Meter. The green and red buttons on the right side of the Control Panel can be used to turn the stirrer on and off as well as the buttons that are on the stirrer itself. Since the dewar and coffee cup are not transparent, the relative amount of solution in the dewar or coffee cup is shown with the level meter.