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Ch 13: Heat and Temperature

Ch 13: Heat and Temperature. Temperature measure of the average KE (motion) of particles (atoms or molecules) Faster they move…more KE…higher temperature Higher temperature…faster they move…more KE. Thermometers.

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Ch 13: Heat and Temperature

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  1. Ch 13: Heat and Temperature • Temperature • measure of the average KE (motion) of particles (atoms or molecules) • Faster they move…more KE…higher temperature • Higher temperature…faster they move…more KE

  2. Thermometers • Thermometers work because the substance (alcohol if it’s red, mercury if it’s silver) heats up, expands and rises • 3 temperature scales oCoF K • water freezes 0o32o273 • water boils 100o 212o 373 • room temp 22o72o295 • body temp 37o98o310 • lowest temp -273o -460o 0 • Kelvin scale is an absolute scale… nothing can go lower than 0K (absolute zero), because at 0K it has no energy…even atoms are frozen

  3. Temperature and Energy Transfer • Things feel hot or cold because energy is being transferred • This transfer of energy is called heat. Amount of heat transferred depends on temp. differences. • Energy flows from high to low concentration, that is from hot to cold things • Why does ice feel cold? • Why does a heater feel hot? • Because heat is leaving your hand • Because heat is entering your hand

  4. Conduction and Convection • when objects are in contact with each other, heat flows directly from the hotter one to the colder one. This is conduction. • fluids (gas or liquid) move and take energy from hotter to colder. This is convection. • if happens in a cycle due to changing densities, it is called a convection current. • Both of these only happen when there is matter present (not in a vacuum, like space)

  5. Radiation • Energy transferred without contact, by electromagnetic waves (visible light, UV, infrared, microwaves, etc.) • Only form of heat transfer that does not need matter to happen, but can happen with matter, too. • Movie: Comparing Convection, Conduction, and Radiation

  6. Where do you see all three?

  7. Conductors and Insulators • Materials that carry/transfer heat energy well are called conductors. Most metal objects are good conductors. • Materials that do not allow heat energy to flow are called insulators. Styrofoam, gasses, wood, plastic and rubber are all good insulators. • So how does styrofoamkeep something both hot and cold? • It doesn’t “know”…it just doesn’t allow heat to transfer either way…in or out.

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