How do thermometers work?
The concept of the thermometer is simple: some colored liquid reaches different heights at different temperatures, and we read these heights as temperature with lines drawn on the thermometer.
So how does this work? Well, generally, things expand when heated and become smaller when cooled (one notable exception is water, which actually expands when frozen). Since the tube of the thermometer is so narrow, when this liquid expands it has no place to go but upwards, so the liquid level rises. So, when heated, the liquid expands and is pushed up, and when cooled, the liquid condenses and moves down, thus allowing us to tell the temperature.
One note about three temperature systems. Fahrenheit, Celsius, and Kelvin. Fahrenheit is the commonly used system of temperature in the United States, but Celsius and Kelvin are the systems used in science, generally. Interestingly, the distance between each Fahrenheit degree is different from the distance between each Celsius degree (which is actually equal to the distance between each Kelvin degree). So the conversion between Kelvin and Celsius is much simpler than the conversion to Fahrenheit. Kelvin is just Celsius + 273. Standard room temperature would be 25 Celsius and 298 K. 0 K is also called absolute zero, where there is zero entropy and is impossible to reach.
Back to thermometers. Many of the ones in the past used mercury as the liquid inside, but rarely do any modern day thermometers contain mercury due to its toxicity (mercury thermometers are still commonly used in meteorology, but rarely are they seen in other subjects). Nowadays, most thermometers use colored alcohol as the liquid.
The concept of the thermometer is simple: some colored liquid reaches different heights at different temperatures, and we read these heights as temperature with lines drawn on the thermometer.
So how does this work? Well, generally, things expand when heated and become smaller when cooled (one notable exception is water, which actually expands when frozen). Since the tube of the thermometer is so narrow, when this liquid expands it has no place to go but upwards, so the liquid level rises. So, when heated, the liquid expands and is pushed up, and when cooled, the liquid condenses and moves down, thus allowing us to tell the temperature.
One note about three temperature systems. Fahrenheit, Celsius, and Kelvin. Fahrenheit is the commonly used system of temperature in the United States, but Celsius and Kelvin are the systems used in science, generally. Interestingly, the distance between each Fahrenheit degree is different from the distance between each Celsius degree (which is actually equal to the distance between each Kelvin degree). So the conversion between Kelvin and Celsius is much simpler than the conversion to Fahrenheit. Kelvin is just Celsius + 273. Standard room temperature would be 25 Celsius and 298 K. 0 K is also called absolute zero, where there is zero entropy and is impossible to reach.
Back to thermometers. Many of the ones in the past used mercury as the liquid inside, but rarely do any modern day thermometers contain mercury due to its toxicity (mercury thermometers are still commonly used in meteorology, but rarely are they seen in other subjects). Nowadays, most thermometers use colored alcohol as the liquid.
