Thermodynamics
9th Grade Science · 8 lessons
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Lessons in this unit
- 1Temperature Versus Internal EnergyTemperature measures the average kinetic energy of particles; internal energy is the total energy of all particles in a body. A bath at 40 °C is cooler than a spark at 1,000 °C but holds far more internal energy, because it contains vastly more particles.Experiment
- 2Conduction, Convection and RadiationConduction passes energy through a solid by particle collisions and free electrons. Convection carries it in a fluid as warmer, less dense regions rise. Radiation needs no medium at all — it is infrared electromagnetic waves, which is how the Sun heats Earth across empty space.Experiment
- 3Specific Latent HeatChanging state takes energy without any temperature change, because the energy goes into breaking bonds rather than speeding particles up. Specific latent heat of fusion is the energy per kilogram to melt; of vaporisation, to boil. Water's latent heat of vaporisation is very large.Experiment
- 4The Particle Model and Gas PressureGas pressure comes from particles colliding with container walls. Heat the gas and the particles move faster, hitting harder and more often, so pressure rises. Shrink the container and collisions become more frequent, which is the origin of Boyle's law.Experiment
- 5Insulation and Rates of CoolingThe rate at which an object cools depends on the temperature difference with its surroundings, its surface area, and how well it is insulated. Trapped air is the key to most insulation, because still air conducts heat poorly.Experiment
- 6Thermal ExpansionMost materials expand when heated because particles vibrate further apart. Engineers allow for it with expansion joints in bridges and gaps in rails. Water is the famous exception below 4 °C, expanding as it freezes, which is why ice floats and pipes burst.Experiment
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