THD - Introduction to Thermodynamics

Thermodynamics

Introduction

Imagine a cup of hot cocoa. If the temperature of the cocoa is too hot, you'll know by how it feels in your hands and in your mouth. To cool it, you might just leave it on the counter for a while. Say you forgot about your cocoa for an hour or so. When you return to it you will find its temperature is cooler. Specifically, it will be the temperature of the room it's been sitting in. Have you ever wondered why it always gets cooler, but never gets warmer when it sits on the counter? In this unit on thermodynamics, you'll learn why heat flows the way it does and how that flow of thermal energy can be put to good use in your daily life.

Essential Questions

1. How are the pressure, volume, and temperature of an ideal gas related?
2. How is thermal energy transferred?
3. How do the First and Second Laws of Thermodynamics relate to the Law of Conservation of Energy?

Key Terms

1. Ideal gas - A theoretical gas consisting of infinitely small molecules that exert no forces on each other.
2. Charles' Law - The volume of a dry gas is directly proportional to its Kelvin temperature, provided the pressure remains constant.
3. Boyle's Law - The volume of a dry gas varies inversely with the pressure exerted on it, provided the temperature remains constant.
4. Ideal Gas Law - The equation that relates the variables of pressure, volume, temperature, and number of moles of gas within a closed system.
5. Thermal equilibrium - When two objects are at the same temperature.
6. Heat - The amount of energy transferred through thermal processes.
7. Conduction - The transfer of thermal energy via the collision of molecules.
8. Convection - The transfer of thermal energy due to the movement of fluids at different temperatures.
9. Radiation - The transfer of thermal energy via electromagnetic waves.
10. 1st Law of Thermodynamics - Defines the internal energy (E) as equal to the difference of the heat transfer (Q) into a system and the work (W) done by the system.
11. 2nd Law of Thermodynamics - In any cyclic process the entropy will either increase or remain the same.
12. Entropy - A measure of the order or disorder of a system.
13. Heat engine - A system that performs the conversion of heat or thermal energy to mechanical work.
14. Specific Heat - The amount of energy necessary to raise the temperature of 1 kg of the substance by 1 °C, or 1 K.
15. Insulator - A substance that does not easily allow heat to flow through it.
16. Conductor - A substance that easily allows heat to flow through it.
17. Thermal Conductivity - An intrinsic property of the material.
18. Law of Conservation of Energy - Energy cannot be created or destroyed, it can only be transferred.

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