Why water is not used in thermometer instead of mercury?

Answer 1

For a thermometer we need a liquid which properly expands and contracts according to the temprature. Water doesn't has that property, i.e. the expansion in water is to small to be used as a liquid in theremometer.

Answer 2

I would guess it is probably due to the fact that water has a none linear thermal expansion (Its thermal expansion coefficient at 20C is not the same as at 90C). Also, at atmospheric pressure, water is only liquidus over a narrow temperature range of 100C which limits its usefulness. Further it has massive problems at phase transitions- for instance when it turns to a gas it consumes a lot of energy (latent heat). A thermometer should have a nice linear response to a rise in temperature. Mercury is a better choice since it doesnt have any phase transitions in the temperature experience in most every day situations. -Just a bit toxic.

Answer 3

Mercury or Alcohol is used as it has a good steady linear thermal expansion over quite a large temperature range.

Water does not behave the same, and it freezes at 0 degrees (and gets larger, thus it would break the glass) and it boils at 100 celcius, so that isn't much use either.

Answer 4

Three reasons:

1. Not visible in small (capillary) glass tube
2. Melting and boiling point to close at interesting temperature range -30 to +100oC
3. Quite variable and small linear expansion factor (increase-length mm per increase-degree temp.) A 'water' thermometer would behave rather strange beneath 4oC: expanding!! at lower temp. before freezing at 0oC

But water&alcohol thermometers are known, and much safer to use: Mercury is toxic when it comes free from broken Hg-thermometers.

Answer 5

because water is a normal liquid that they cannot measuring like temperature and because water has a oxygen that they can use in high measuring.