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Thermal Physics

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

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  1. Thermal Physics

  2. Thermal Physics • Describe the image  • What is it? • What does it measure? • How does it work?

  3. 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?

  4. 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?

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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.

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