THE HEAT OF COMPRESSION Submitted by: L. Gachic, Regis College, Denver, Colorado d Checked by: Joseph M.Dasbach, Center for E d ~ ~ c a t i o nTech"
Catholic University of America, Washington, D. C. 20007
PREPARATION Provide apparatus consisting of a sensitive galvanometer such as the Weston Model 441, a thermocouple, a .&mi hypodermic syringe, and an iron-constant thermoconple. (Both wires are 30 gauge,) The conple is made in the ~15ualmanner. In addition have available a stick of sealing wa.xsnch as is fmnd in stationery stores.
DEMONSTRATION One iunctmn of the thenn~co11~le 1s bealed 111 the lower end of t,he hvmdermic svrince with sealine wax. The other i~mctionis couple. Heating occurs when the gas (air) is quickly compressed and the galvanometer needle deflects to one side of zero. Expanding the gas by rapidly pulling the phmger m t causes a deflection of the galvanometer needle in the opposite direction, Two or more couples may be used for a greater deflection.
REMARKS That the gas is heating on compression may he verified hy holding the exposed free junction hetween the fingers, the deHec-
A demonstration of the h e m of compression
will he oppo3ite to by collple the syringe. The heat of vaporization and condensztion can also he demonstrated by adding several drops of acetone to the hypodermic syringe. The deflection of the galvanometer will be considerably greater than when air is compressed orexpanded. Journal of Chemical Educat
