Additional Info

• ID Code: I5-41
• Purpose: Aid a discussion of entropy.
• Description: 31.5 grams of barium hydroxide and 15.2 grams of ammonium thiocyanate, both solid powders initially at room temperature, are mixed. As they are stirred using the digital thermometer probe a chemical reaction occurs, producing water with barium cyanate and ammonium, both of which are soluble in the water. The solution becomes very cold, and can freeze a wettened wooden block to the bottom of the beaker.

  This experiment can be described in terms of entropy using two approaches: (1) As the mixture cools, it must become a liquid, increasing its disorder so that entropy will increase, or (2) The tendency toward disorder drives the reaction, creating the liquid reaction product.

  Note: PLEASE CALL THE LECTURE DEMONSTRATION GROUP AT 405-5995 NOT LATER THAN THE MORNING BEFORE YOUR REQUEST SO THAT WE HAVE THE TIME TO PREPARE THE NEEDED CHEMICALS.

• Availability: Available
• References: REFERENCES: (PIRA unknown.)