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Physical Science. Heat and Thermodynamics Chapter 16 Section Two. Science Journal Entry 30. Explain the differences and similarities, between conduction, convection and radiation. Conduction.
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Physical Science Heat and Thermodynamics Chapter 16 Section Two
Science Journal Entry 30 • Explain the differences and similarities, between conduction, convection and radiation.
Conduction • Conduction is the transfer of heat energy by direct contact. No matter is transferred only energy. • Conduction in gases is slower than in liquids and solids because the particles in a gas collide less often since they are farther apart. • Conduction is faster in metals, not only because they are solid but because some electrons in them are free to move about. • A thermal conductor is a material that conducts thermal energy well. A thermal insulator is a material that conducts thermal energy poorly.
Convection • Convection is the transfer of thermal (heat) energy when particles of a fluid move from one place to another. • A Convection Current circulates within a fluid as the fluid alternately heats up and cools down. The warm fluid (even air) rises but the colder fluid sinks creating a loop-like cycle. Convection currents occur in many important natural cycles, such as ocean currents, weather systems, and movements of hot asthenosphere in Earth’s Interior.
Radiation • Radiation is the transfer of heat energy by electromagnetic waves such as the solar radiation of the sun or a radiator providing heat for an apartment. • All objects radiate energy. As an object’s temperature increases, the rate at which it radiates energy increases. • https://youtu.be/-7SRr-bnsKY 5:05
First Law of Thermodynamics • Thermodynamics is the study of conversions between heat and other forms of energy. • James Prescott joule is usually given the credit for discovering the First Law of Thermodynamics. • The First Law of Thermodynamics states that the energy is conserved. Internal energy (U) of a system changes from an initial value to a final value due to Heat (Q) minus Work (W).
Second Law of Thermodynamics • The second law states that Heat Flows Spontaneously from a Substance at a Higher Temperature to a Substance at a Lower Temperature and Does Not Flow Spontaneously in the Reverse Direction unless work is done. https://youtu.be/VtEqn-5XHpU • 2:11
From Order to Disorder The second law also shows that all systems naturally tend toward disorder. Entropy is a Measure of the Disorder of a System. Work is required to maintain or increase order. Thermal energy that is not converted into work is called waste heat. A heat engine is a device that converts thermal energy into work. A heat engine can do work only if some waste heat flows to a colder environment. • https://youtu.be/34CON9NtiKE 2:15 • https://youtu.be/ykUmibZHEZk 5:06 Asylum
Third Law of Thermodynamics • The third law of thermodynamics states that absolute zero cannot be reached. All matter has kinetic energy within it because its particles will always be moving. • Absolute zero would be the state at which the molecules in a substance do not move at all. This has never happened. • https://youtu.be/hBqcGWzHQbY 1:35 • https://youtu.be/7T8a8xZRHiY 3:07
Conclusion • The first law of thermodynamics states that energy is conserved. • The second law of thermodynamics states that thermal energy can flow from colder objects to hotter objects ONLY if work is done on the system. • The third law states that absolute zero cannot be reached.
