A thermometer is a device or instrument used for measuring temperature. There are many different types of thermometers; however each one is based on a physical property of a thermometric (temperature measuring) substance that differs in a measurable way with temperature. Some of the physical properties that vary with temperature are volume, resistance and color. A physical property that increases or decreases with temperature can be used to measure temperature. This is called a thermometric property.
There are two types of liquid-in-glass thermometers: 1) Mercury-In-Glass Thermometers 2) Alcohol-In-Glass Thermometers. A liquid in glass thermometer uses mercury or alcohol as its thermometric substance. Its thermometric property is volume and it is used to measure the temperature by allowing the mercury or alcohol to expand or contract in the capillary tube as temperature rises or decreases. I.e. an increase in temperature equals an increase in volume while a decrease in temperature equals a decrease in volume. A mercury-in-glass thermometer has a range of -39oC to 360oC while an alcohol-in-glass thermometer has a range of -112o C to 78o C.
Here are some advantages and disadvantages of mercury-in-glass thermometers:
* It doesn’t cling to the sides of the tube.| * It’s expensive.| * It expands uniformly.| * Its freezing point is high at -39oC| * It has a visible surface that makes it easily seen in fine capillary tubes.| * It’s poisonous.| * It is a good conductor of heat, which makes it reach the exact temperature faster.| * It cannot expand a great deal.| * Its boiling point is high at 375o C.| |
Here are some advantages and disadvantages of alcohol-in-glass thermometers:
* Its expansion is uniform.| * It sticks to the tube.| * It can...