Why is water not used in barometer?
Water is not a suitable barometric liquid because: (i) The density of water is low (103 kg m-3). Water barometer will support 10.4m of water at sea level. It is impractical to have such a long tube.
Why water is not used in thermometers instead of mercury?
Water cannot be used in thermometer because of its higher freezing point and lower boiling point than other liquids . This range is very small as compared to other liquids as mercury , having freezing point about −39oC and boiling point 356oC .
Why do we prefer mercury in thermometers?
Mercury is the only one in liquid state at room temperature. It’s used in thermometers because it has high coefficient of expansion. Hence, the slightest change in temperature is notable when it’s used in a thermometer. It also has a high boiling point which makes it very suitable to measure higher temperatures.
Which thermometer is better to use water or mercury?
Below 0oC and above 100oC can’t measure by using the water. The most metals are solids at room temperature but the mercury is liquid form because it has high coefficient of expansion. The mercury does not sticking to capillary wall of thermometer can easily measure temperature accurately.
Can water be used instead of mercury What are the problems in using it?
Answer. We use mercury in thermometers because most metals are good conductor of heat and mercury is the only metal in liquid state. No,we cannot use water instead of mercury because water do not expand as per temperature given to it and can give us wrong reading.
What are the melting and boiling points of mercury?
Mercury has a melting point of -38.9oC, a boiling point of 356.7oC, and is the only metal to remain in liquid form at room temperature.
Can you suggest alternatives to mercury thermometers?
There are numerous alternatives to mercury thermometers. But increasingly, selecting an alternative to Hg is chiefly a matter of choosing among one of the three sensor types used in digital thermometry: platinum resistance (PRT), thermistor, and thermocouple.
What is used in thermometers instead of mercury?
Ethanol-filled thermometers are used in preference to mercury for meteorological measurements of minimum temperatures and can be used down to −70 °C (−94 °F). The physical limitation of the ability of a thermometer to measure low temperature is the freezing point of the liquid used.
What can we use instead of mercury?
Spirit thermometers use a non-toxic alcohol instead of mercury to register the temperature. Like liquid mercury, the alcohol expands in volume as it gets warmer, causing the liquid to move up the thin tube inside the glass thermometer. Digital thermometers contain a device called a thermoresistor.
How long do you hold a mercury thermometer in your mouth?
ORAL TEMPERATURE After shaking the mercury down, place the thermometer under the child’s tongue, with the bulb toward the back of the mouth. Tell your child to keep the lips firmly closed, but not to bite the thermometer. 3. Leave the thermometer in place for 3 minutes.
How do you calibrate a mercury thermometer?
Place the stem of the thermometer in the boiling water. Again, make sure that it’s submerged at least 2 inches and wait at least 30 seconds. Your thermometer should read 212°F or 100°C. If it doesn’t, keeping the thermometer in the water, turn the adjusting knob until the needle reaches the 212°F mark.
How accurate are mercury free thermometers?
Non-mercury thermometers have scale divisions equal to mercury thermometers. Most range from 0.5° to 1° C. Accuracy limits for non-mercury thermometers below 150° C are also compatible with mercury thermometers; accuracy is typically ± 1° – 2° C.
Do you have to shake down a mercury free thermometer?
Very accurate thermometer. It is difficult to shake down, so get a sock, and put the thermometer inside the case in the sock.
How long does a mercury free thermometer last?
This handy thermometer contains Galinstan®, an environmentally-friendly alternative to mercury, and is safe to clean up with mild soap and water if it breaks. Simply place the thermometer under the tongue for 3 minutes for proven clinical accuracy.