vsh@pixel.UUCP (vsh) (10/23/85)
Here's an old puzzler from my high school science days, but which may
tantalize a few of you:
When an ordinary mercury thermometer at room temperature is inserted
into a beaker of boiling water, the mercury actually descends a
small but noticeable amount before ascending to the 100 C level.
Why?
Try it yourself.
--
Steve Harris
Pixel Systems Inc.; 300 Wildwood St.; Woburn, MA. 01801
(617) 933-7735 x2314 (work) (617) 664-0099 (home)
{allegra|ihnp4|cbosgd|ima|genrad|amd|harvard}!wjh12!pixel!vshmeister@linus.UUCP (Phillip W. Servita) (10/24/85)
In article <24@pixel.UUCP> vsh@pixel.UUCP (vsh) writes: >Here's an old puzzler from my high school science days, but which may >tantalize a few of you: > >When an ordinary mercury thermometer at room temperature is inserted >into a beaker of boiling water, the mercury actually descends a >small but noticeable amount before ascending to the 100 C level. >Why? The glass must conduct the heat to the mercury inside. Hence the cylindrical hole inside expands before the mercury does. -the venn buddhist -- ----------------------------------------------- "Of course the Nielsen ratings are accurate... We proved it in a taste test!" ----------------------------------------------- -the venn buddhist
ejb@think.ARPA (Erik Bailey) (10/25/85)
In article <24@pixel.UUCP> vsh@pixel.UUCP (vsh) writes: >When an ordinary mercury thermometer at room temperature is inserted >into a beaker of boiling water, the mercury actually descends a >small but noticeable amount before ascending to the 100 C level. >Why? Well, my friend Dave Whitney says: It's because when you put the theremometer in the hot air rising from the boiling water, there is a distinct drop in pressure, uh, causing the bulb of glass around the mercury to expand, and therefore sucking the murcury down the thermometer. --Erik
hes@ecsvax.UUCP (Henry Schaffer) (10/26/85)
> When an ordinary mercury thermometer at room temperature is inserted > into a beaker of boiling water, the mercury actually descends a > small but noticeable amount before ascending to the 100 C level. > Why? > > Steve Harris Before the mercury can expand because of the heat, the glass surrounding the mercury must get hot to pass on the heat. The glass does expand somewhat *before* the mercury heats up. This expansion increases the volume of the "container" holding the mercury, and so the mercury will descend. For a small (rate of) change in the temperature the effect should be very small, but room temp. to boiling water is not a small change. --henry schaffer