Temperature – Fundamentals Module #10
Last post we talked about sensible and latent heats, after building up our foundation with molecules and energy talk. This engineering fundamentals post is going to go over temperature. Okay smarty pants.
What is Temperature?
The temperature scales typically used to measure temperature are the Fahrenheit (F) scale and the Celsius (C) scale. In America, the Fahrenheit scale is typically used. I have no clue about the rest of you cavemen in other parts of the world (I kid. I use and appreciate both systems.) You may, however, have to convert Celsius readings to the Fahrenheit scale, so both scales are explained here. And since the 90’s I have only seen the use of the metric system rise in America and the building engineering field. Measurements for water treatment analysis are performed using the Celsius scale.
The Fahrenheit scale has two main reference points—the boiling point of pure water at 212°F and the freezing point of pure water at 32°F. The measure of a degree of Fahrenheit is 1/180 of the total temperature change from 32°F to 212°F.
The scale can be extended in either direction—to higher temperatures without any limits and to lower temperatures (by minus degrees) down to the lowest temperature theoretically possible, absolute zero. This temperature is – 460°F, or 492°F below the freezing point of water.
In the Celsius scale, the freezing point of pure water is 0°C and the boiling point of pure water is 100°C.
Therefore, 0°C and 100°C are equivalent to 32°F and 212°F, respectively.
Each degree of Celsius is larger than a degree of Fahrenheit. Only 100° Celsius are between the freezing and boiling points of water, while this same temperature change requires 180° on the Fahrenheit scale.
Therefore, the degree of Celsius is 180/100 or 1.8° Fahrenheit. In the Celsius scale, absolute zero is – 273°C.
How to convert temperature
To convert from one temperature scale to another, use these equations:
From Fahrenheit to Celsius:
°C = 5/9 X (°F – 32)
From Celsius to Fahrenheit:
°F = (9/5 x °C) + 32
Imagine two star crossed thermometers…
One a Fahrenheit, the other having a Celsius scale. They love each other but like Romeo and Juliet, they simply weren’t meant to be. Don’t worry your scientific head though the principles are the same.
The main point to remember is that the liquid level in a thermometer depends only on the temperature to which the bulb is exposed.
If you were to exchange the thermometers, the liquid in the Celsius thermometer would drop to the level that the liquid now stands in the Fahrenheit thermometer. Likewise, the liquid in the Fahrenheit thermometer would rise to the level that the liquid now stands in the Celsius thermometer. The temperatures would be 0°C for the ice water and 212°F for the boiling water.
If you place both thermometers in water containing ice, the Fahrenheit thermometer will read 32°F and the Celsius thermometer will read 0°C. Heat the water slowly.
The temperature will not change until the ice in the water has completely melted (a great deal of heat is required just to melt the ice). Then both thermometer liquid columns will begin to rise. When the level is at the +10° mark on the Celsius thermometer, it will be at the +50° mark on the Fahrenheit thermometer.
The two columns will rise together at the same speed and, when the water boils, they will stand at 100°C and 212°F, respectively.
The same temperature change—that is, the same amount of heat transferred to the water—has raised the temperature 100° Celsius and 180° Fahrenheit, but the actual change in heat energy is exactly the same.
Temperature is a kind of a little easier to understand but also a bit more complex than what is on the surface isn’t it? Once again, everything, EVERYTHING in life is about energy and energy conversions. Temperature is another way for us to measure it so that we can understand it and utilize it better.