Thermal Physics

Describe the image

◦ What is it?

◦ What does it measure?

◦ How does it work?

Thermal Physics

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?

Thermal Temperature

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?

Thermometric Properties

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)

Temperature Scales

TC = (5/9) (TF - 32)

TK = TC + 273.15

Freezes: 32° F = 0° C = 273.15 KBoils: 212° F = 100° C = 373.15 K

At standard pressure!1 atm760 mm Hg (Torr)101,325 Pa = 101.325 kPa1.01325 bar

Conversion Example : Water

Water – Phase Diagram

Triple Point – Water, Ice, and Steam exist

Critical Point – Above this point, the liquid phase and gas phase merge into 1 phase, a supercritical fluid

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 ofKE values

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

Internal Energy Total E

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

3 Ways to Transfer Thermal 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.

What is the difference between heat, temperature, and internal energy?