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NS 3310 – Physical Science Studies. Chapter 4 – Heat and Temperature. Key Questions. What is heat? What is thermal energy? What is temperature? Is there a difference? How does heat move around? Why do some things feel hot and others cold?
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NS 3310 – Physical Science Studies Chapter 4 – Heat and Temperature
Key Questions • What is heat? What is thermal energy? What is temperature? Is there a difference? • How does heat move around? • Why do some things feel hot and others cold? • How do substances change their state of matter? How is heat involved? • What are the laws of thermodynamics? • What is entropy?
Kinetic Energy of Molecules • Solids • Fluids • Liquids • Gases • Plasmas
Temperature • Temperature measures the kinetic energy of molecules (this is external energy) • Fahrenheit • Celsius • Kelvin (absolute zero)
Thermal Energy • Thermal energy is the internal energy of a molecule • Heat is a measure of the internal energy that has been absorbed or transferred from one body to another • Heat is measured in calories (c) or British Thermal Units (BTUs)
Specific Heat and Latent Heat • Specific heat changes the temperature of an object • Latent heat changes the phase of the material • For example: Ice to Water to Steam
Phase Transitions • Latent Heat of Fusion / Melting • Latent Heat of Vaporization / Condensation • Relative Humidity
Heat Flow • Radiation • Conduction • Convection
Thermodynamics • The First Law of Thermodynamics • Applied Law of Energy Conservation • W = J(QH – QL) • The Second Law of Thermodynamics • Heat always flows from an area of higher concentration to an area of lower concentration • Entropy
Perpetual Motion Machine? • Perpetual Motion Machines • Free Energy • Other Scams
Key Concepts • Thermal energy is the internal and external energy of atoms. • Heat is the transfer of thermal of energy between atoms. • Temperature is a measurement of the kinetic energy of molecules. • Adding heat energy to substances makes their temperature rise (specific heat). • To change the state of a substance requires even more heat (latent heat). • Heat can be transferred by radiation, conduction and convection. • Entropy describes the total energy of a system and tells us that we cannot get more energy out of a system than we put into it.