PHY 2020 Lecture Notes - Lecture 11: Thermal Expansion, Boiling Point, Melting Point

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16 Nov 2017

School

University of Florida

Department

Physics

Course

PHY 2020

Professor

Sergei Obukhov

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Document Summary

All matter comprises atoms and molecules that are constantly jiggling and shaking. By virtue of this motion, the atoms have kinetic energy. This energy is known as thermal energy, and temperature a measure of the average energy of the individual particles and corresponds to what we know as hot and cold. As a metal, the hg expands when it gets hot: freezing point of water = 0 c (273 k; 32 f, boiling point of water = 100 c (373 k; 212 f) (cid:894) f-(cid:1007)(cid:1006)(cid:895)5/9 = c, 9/5( c)+32 = f. 11. 2: how temperature affects gas properties: volume is directly proportional to temperature cha(cid:396)les" la(cid:449), pressure is directly proportional to temperature, pressure is inversely proportional to volume, product of pv is proportional to t. In the ideal gas law, temperature must always be in k. 11. 3: heat transfer and heat capacity: calorie (=1 kcal) vs calorie.

Related Questions

The kinetic theory of gases states that the kinetic energy of a gas is directly proportional to the temperature of the gas. A relationship between the microscopic properties of the gas molecules and the macroscopic properties of the gas can be derived using the following assumptions: The gas is composed of pointlike particles separated by comparatively large distances. The gas molecules are in continual random motion with collisions being perfectly elastic. The gas molecules exert no long-range forces on each other. One of the most important microscopic properties of gas molecules is velocity. There are several different ways to describe statistically the average velocity of a molecule in a gas. The most obvious measure is the average velocity Vavg. However, since the molecules in a gas are moving in random directions, the average velocity is approximately zero. Another measure of velocity is (V^2)avg, the average squared velocity. Since the square of velocity is always positive, this measure does not average to zero over the entire gas. A third measure is the root-mean-square (rms) speed,Vrms , equal to the square root of (V^2)avg. The rms speed is a good approximation of the the typical speed of the molecules in a gas. This histogram (Figure 1) shows a theoretical distribution of speeds of molecules in a sample of nitrogen () gas. In this problem, you'll use the histogram to compute properties of the gas.

Part A

What is the average speed

of the molecules in the gas?

Part B

Because the kinetic energy of a single molecule is related to its velocity squared, the best measure of the kinetic energy of the entire gas is obtained by computing the mean squared velocity, $(v^2)_{\rm avg}$ , or its square root. The quantityis more common than $(v^2)_{\rm avg}$ because it has the dimensions of velocity instead of the less-familiar velocity-squared.