help me to answer this please!!?

Question

1. Some laboratory thermometer use alcohol instead of mercury, what are the advantages and disadvantages in using alcohol in thermometers?
2. Why is clinical thermometer usually shaken before use?
3. For liquids with boiling points below 100°C w/c thermometer could register a more accurate reading, the one with a maximum temperature of 110°C or one that register temp up to 300°C? Assume that both thermometers are of equal length.
4. Why is a small gap left between railroad tracks instead of welding them together?
5. In chemistry, platinum wires are embedded into glass rods for flame test experiment. Why is copper wire which is cheaper and readily available not used instead?

Answer 1

Arwin, get off of that darned computer and DO YOUR OWN HOMEWORK!

Answer 2

I'm not sure about the first, but for the others:

2: Clinical thermometers have restrictions above the bulb which prevents the fluid from contracting back into the bulb when the temperature drops. This is so the reading can be taken after the thermometer is removed from the body--it will hold the reading. In order to get the liquid back into the bulb, the thermometer is shaken.

3 The 110ºC range is more *precise* because the divisions are wider, there are more intermediate marks, and interpolation is easier. This does not mean more accuracy, as that depends on the calibration of the thermometer. However, if the calibrations are equivalent, the 110º thermometer will be more accurate as well.

4. The gap allows for expansion of the rails as the temperature increases; otherwise they will buckle

5. You can't use copper for flame tests because copper has a strong blue flame color that would obscure the color of the material being tested.

Answer 3

Alcohol is preferred to mercury because it is cheaper, less toxic, and has a lower freezing point. The classical fever thermometer used mercury, and had to be shaken before use because the capillary tube was so small in diameter that the surface tension of the mercury was not sufficient to retract the column. (Alcohol, with a lower surface tension, would have been worse.)

For measurning temperatures near 100 C, the 110 C thermometer would be preferred because the temperature graduations would be farther apart and could be read more accurately.

Gaps are left between railroad rails to allow for thermal expansion on a hot day.

Copper is unsuitable for flame test wire because it contributes a color of its own. Platinum does not.

Answer 4

1. Alcholo is preferred because if your experiment fails you can drink the thermometer.