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Thermal Physics. Thermal Physics . Describe the image What is it? What does it measure? How does it work?. Thermal Temperature. What is it? Scalar Provides information about how hot or cold something is Measured with a Thermometer
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Thermal Physics • Describe the image • What is it? • What does it measure? • How does it work?
Thermal Temperature • What is it? • Scalar • Provides information about how hot or cold something is • Measured with a Thermometer • Temperature noted on the thermometer is equal to that of the object when the two are in equilibrium • How do thermometers work?
Thermometric Properties • Physical properties of matter can change dependent on temperature • Thermometers follow 1 of the principles • Thermal Expansion of a liquid • Electrical Resistance of a wire • Pressure of a gas (in a fixed volume) • Linear Expansion of Solids • Color of a solid heated to high temperatures • How would you make a thermometer?
Temperature Scales • Fahrenheit (1724) • Salt:water:ice mixture and body temperature • Celsius (1742) • Freezing and boiling point of water • Kelvin (1848) • Gas Expansion Coefficient and Celsius • Fundamental unit for temperature • At 0 K, all molecules stop moving (theoretically) TC= (5/9) (TF- 32) TK= TC+ 273.15
Conversion Example : Water • Freezes: 32° F = 0° C = 273.15 K • Boils: 212° F = 100° C = 373.15 K • At standard pressure! • 1 atm • 760 mm Hg (Torr) • 101,325 Pa = 101.325 kPa • 1.01325 bar
Water – Phase Diagram Critical Point – Above this point, the liquid phase and gas phase merge into 1 phase, a supercritical fluid Triple Point – Water, Ice, and Steam exist
Temperature Avg EK of molecules • For Gases: EK = (3/2)k*T • EK Kinetic Energy • T Temperature • k Boltzmann Constant • k = 1.38 x 10-23 JK-1 • Distribution of KE values
Internal Energy Total E • Internal E = PE + KE of all particles within the system • Potential Energy • Bond Energy – energy stored in bonds • Intermolecular forces – attractive energy between particles • Kinetic Energy - movement • Translational - straight line • Rotational – spinning about an axis • Vibrational – back and forth motion centered at a point • Solids – mainly vibrational • Liquids – mainly vibrational, some rotational, little translational • Gases – Mainly translational and rotational
3 Ways to Transfer Thermal Energy • Conduction – Physical contact hot cold • Particle collisions – no net movement • Gases – slow; Liquids – medium; solids – fast (metals) slow (generally non-metals) • Convection – movement of fluids cold hot • Only fluids • Density differences in fluids • Hot – more energy, further apart, lower density • Cold – less energy, closer together, higher density • Radiation – light is released and absorbed • No matter necessary for transfer • EX: SUN
What is the difference between heat, temperature, and internal energy? • Heat – energy that is transferred due to temperature differences • Temperature – measure of AVG. kinetic energy of the molecules in a substance • Internal Energy – total kinetic energy and potential energy associated with forces and bonds among the molecules in a substance.