Temperature - Molecular Interpretation, Thermometers And Temperature Scales, The Fahrenheit Scale Of Temperature, The Celsius Scale
energy heat water finger
Temperature is intuitively associated with the sense of hot and cold. Put your finger in a pan of hot water and energy flows as heat from the water to your finger; you say that the water is at a higher temperature than your finger. Now put your finger in a glass of ice water and energy flows as heat in the other direction. The direction of energy flow as heat is the basis of our definition of temperature. Temperature is the property of objects—or more generally, systems—that determines the direction of energy flow as heat when the objects are put in direct contact with each other. Energy flows as heat from objects at higher temperature to ones at lower temperature. When energy as heat ceases to flow, the objects are at the same temperature and are said to be in thermal equilibrium.
Additional Topics
At the molecular level, temperature is related to the random motions of the particles (atoms and molecules) in matter. Because there are different types of motion, the particles' kinetic energy (energy of motion) can take different forms, and each form contributes to the total kinetic energy of the particles. For example, when water squirts from a hose, part of the kinetic energy of the wat…
There is no easy way to measure directly the average molecular translational energies in an object. Therefore, temperature is determined indirectly by measuring a temperature-dependent property of a device that is in thermal equilibrium with the object to be measured. We call such a device a thermometer. One of the earliest kinds of thermometers, still in use today, has a liquid in a glass bulb at…
In 1714, the German physicist Daniel Gabriel Fahrenheit (1686-1736) made a better choice by selecting liquid mercury. Mercury has a uniform volume change with temperature, a lower freezing point and higher boiling point than water, and does not wet glass. Mercury thermometers made possible the development of reproducible temperature scales and quantitative temperature measurement. Fahrenheit first…
In 1742, the noted Swedish astronomer Anders Celsius (1701-1744), professor of astronomy at the University of Uppsala, proposed the temperature scale which now bears his name, although for many years it was called the centigrade scale. As with the Fahrenheit scale, the reference points were the normal freezing and normal boiling points of water, but he set them to be 100° apart instead of 1…
About 1787 the French physicist, Jacques Charles (1746-1823) noted that a sample of gas at constant pressure regularly contracted by about 1/273 of its volume at 0°C for each Celsius degree drop in temperature. This suggests an interesting question: If a gas were cooled to 273° below zero, would its volume drop to zero? Would it just disappear? The answer is no, because most gases wi…
The highest recorded weather temperature on Earth was 136°F (57.8°C), observed in North Africa in 1922. The record low temperature is -129°F (-89.2°C), observed in the Antarctic in 1983. Elsewhere in the universe, temperature extremes are much greater. The average surface temperatures of the most distant planets in our solar system (Uranus, Neptune, Pluto) are about 53K…
Citing this material
Please include a link to this page if you have found this material useful for research or writing a related article. Content on this website is from high-quality, licensed material originally published in print form. You can always be sure you're reading unbiased, factual, and accurate information.
Highlight the text below, right-click, and select “copy”. Paste the link into your website, email, or any other HTML document.
User Comments