2006-09-19 23:27:08 · 7 answers · asked by unao12345 1 in Science & Mathematics ➔ Other - Science
Good question!
Because of two factors: the surface tension of the fluid used and the capillarity of the glass tube.
The fluid in the thermometer expands or contracts with temperature variations. This expansion/contraction changes the VOLUME of the fluid, but very, very, very little. (Check coefficent of expansion of the fluid). To show a small difference such as one degree, we amplify the change by passing the fluid into a cylinder of very small diameter (capillary), so the section is small and the hight of the cylinder is larger.
At the top of the column of fluid, it faces a vacuum, but the SURFACE exposed to the vacuum is extremely small (the diameter of the capillary), and the superfical tension of the fluid is enough to act as a "cork"... and prevents the fluid from going down when the thermometer is upside-down. (Should the diameter of the capillary be larger, the fluid WOULD flow down).
2006-09-19 23:46:42 · answer #1 · answered by just "JR" 7 · 0⤊ 0⤋
The molecules of mercury (or red-dyed alcohol) cling to each other preventing the column from falling unless a vacuum is produced at the "top" like in a mercury barometer that is about 30 inches tall. The ability to cling together is called surface tension and that is why spilled mercury forms into tiny spheres. Rain drops are also perfect spheres due to the surface tension of water. A valuable lab thermometer should be stored right side up rather than upside down because the liquid column actually can separate.
2006-09-20 08:22:06 · answer #2 · answered by Kes 7 · 0⤊ 0⤋
This is because of the density of the liquid in the termometer (usually mercury). Low of gravity also plays a part in making the liquid stays intact when you turn the termometer upside down.
Law of Physics
2006-09-20 06:37:55 · answer #3 · answered by Calista 1 · 0⤊ 1⤋
This is because there is a constrictor in the thermometer which prevent the liquid from flowing down. To overcome the force of the constrictor, you would have to shake the thermometer vigorously.
Trust me. I got this question right in my 4th grade exam.
2006-09-20 07:07:18 · answer #4 · answered by Hardrock 6 · 0⤊ 0⤋
because the liquid you see is in the part of the thermometer that is a very tiny tube, the liquid can not flow down because air bubbles can not flow up in the same tube to change place with the liquid.
2006-09-20 06:43:58 · answer #5 · answered by Anonymous · 0⤊ 1⤋
Gravity pulls everything. Study physics.
2006-09-20 06:35:51 · answer #6 · answered by K Ban 2 · 0⤊ 2⤋
because the laws of physics
2006-09-20 06:34:58 · answer #7 · answered by haringrobert 3 · 0⤊ 2⤋