1 / 17

Exploring Thermal Physics: Temperature, Energy, and Equilibrium

Learn about thermal physics, including temperature scales, thermal expansion, ideal gases, and kinetic theory of gases. Discover key concepts like thermal equilibrium and thermal expansion of solids and liquids.

vmonica
Download Presentation

Exploring Thermal Physics: Temperature, Energy, and Equilibrium

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Thermal Physics • Thermal Physics is the study of temperature and heat and how they effect matter. • Heat leads to change in internal energy which shows as a change of temperature and is evident with the expansion or contraction of matter

  2. Temperature • Temperature is the hotness or coldness of matter • Heat energy travels from a hot object to a cold object • If two objects are in contact thermal contact energy can be exchanged between them • The exchange of energy is called heat

  3. Thermal Equilibrium • Two objects are in thermal equilibrium if they are in contact and no exchange of energy takes place • Zeroth Law of Thermodynamics states that if object A and B are in thermal equilibrium with object C then A and B are in thermal equilibrium with each other. • Two objects in thermal equilibrium have the same temperature.

  4. Thermometers • A thermometer is a calibrated device to measure temperature. They are much smaller than the system so they can reach equilibrium without great loss of energy from the system.

  5. Types of Thermometers • Change in volume of liquid (Mercury) • Length change of a solid • Change of pressure of gas with constant volume. (change of v with constant p) • Electric resistance of a conductor • Change of color of a hot object

  6. Temperature Scales • Kelvin calibrated using a gas thermometer Absolute zero = 0 Kelvin = - 273.15c Triple point of water is where ice, water and water vapor coexist. At 0.01oc and 4.58 mm Hg is used to establish Kelvin scale. • Celcius scale TC = TK- 273.15 • Fahrenheit scale TF = 9/5TC + 32

  7. Thermal expansion of solids and liquids • As the temperature of a substance increases the volume increases. Thermal expansion occurs due to a change in the average separation of the constituent atoms or molecules. • Atoms in a solid a separated by an average of 10-10m and vibrate. As temperature increases so does the separation.

  8. Linear Expansion • Let Lo be the original length  be the coefficient of linear expansion ΔT be the change in temperature Then ΔL =  LoΔT • Coefficient are published values particular to the type of material

  9. Area Expansion • Let the lengths of the sides be = L then A = L2 let Ao = original area ΔA = Ao ΔT •  is the coefficient of area expansion

  10. Volume Expansion • Similar to both length and area expansion volume expansion can be shown as Δv = vo ΔT  is the coefficient of volume expansion • Note that  = 2  and  = 3  • Liquids generally have volume coefficients ten times greater than solids

  11. Ideal Gas • An ideal gas is one that has atoms or molecules that move randomly and have no long range forces on each other. Each particle is like a point. • 1 Mole of gas has 6.02*1023 particles • 1 mole of gas occupies 22.4 liters

  12. Ideal Gas Equation • Pv = nRT • R is the ideal gas constant R= 8.31 when using Pa and m3 R= 0.0821 when using atmospheres and liters

  13. Kinetic Theory of Gases • The number of atoms/ molecules in a gas are large and the average separation is great compared to their size • particles obey Newton’s laws of motion and move randomly • Particles interact only through short range forces having elastic collision, including walls • All molecules in a gas are identical

  14. Boltzmann’s Constant • From Pv = nRT you get Pv = kBRT where kB = n/NA NA = Avogadro’s number = 6.02 * 1023

  15. Force on Container Walls • F = N/3(mv2/d) • where N = number of particles m = mass of one particle v = the average speed of the particles d = the length of the edge of the container • Total pressure on the walls of the container • P = 2/3(N/vc)(1/2mv2) vc= container volume

  16. Molecular Interpretation of Temperature • Temperature of a gas is a direct measure of the average molecular kinetic energy of the gas particles. 1/2mv2 = 3/2kBT • Total translational kinetic energy of N particles KEtotal = N(1/2mv2) = 3/2NkBT • For monatomic gases translational KE is the only type of energy the particles have. • Where U = 3/2nRT

  17. Root-Mean-Square • Diatomic and polyatomic gases have additional energies due to vibration and rotation. Their average velocity is calculated from • vrms = • m = molar mass in kg per mole

More Related