Thermal Energy Warm Up: To shape metal into a horseshoe, the metal is heated in a fire. Why will a horseshoe bend when its very hot, but not after it cools? What was different ? There was more motion in the hot water Matter is always in motion Particles of gases, liquids, and solids all move The energy of motion is Kinetic Energy Heat Heat is the transfer of thermal energy from one object to another because of a temperature difference. Heat flows spontaneously from hot objects to cold objects. Heat Heat is related to temperature: The Temperature of an object is the measurement of the average kinetic energy (KE) of particles As an object heats up its particles move __________________ on average. As a result, the average kinetic energy (and the temperature) _________________. Number of collisions between particles increases. Thermal energy is transferred from hot to cold objects. What do Temperature Scales Measure? Fahrenheit: used in US Celsius: used in other countries Kelvin: SI unit 0 K = -273C 0C = 273 K Thermal Energy Thermal Energy (Q) is the sum of the kinetic energy + the potential energy of all the particles in an object: Thermal energy depends on the mass, temperature and phase (solid, liquid, or gas) of an object. Q = KE + PE Thermodynamics First Law of Thermodynamics: the increase in thermal energy of a system equals the work done on the system plus the heat transferred to the system Energy is CONSERVED Open Systems In an open system, heat flows across the boundary, or work is done across the boundary. What are examples of open systems? Closed Systems In a closed system, no heat flows across the boundary and no work is done across the boundary. What are examples of closed systems? Thermodynamics Second Law of Thermodynamics: Heat flows from warmer objects to cooler objects Heat cannot flow from a cooler object to a warmer object unless work is done How do solids transfer heat? Conduction: the transfer of thermal energy by collisions between particles in matter. Particles in solids vibrate and collide with each other List 3 examples of conduction Convection Convection is the transfer of thermal energy in a gas or liquid by the movement of warmer and cooler fluid from place to place. Knowing this, what will happen to a piece of ice floating at the top of a warm glass of water? What will happen to a piece of ice at the bottom of a glass of water? List 3 examples of convection Radiation Radiation is the transfer of energy by electromagnetic waves. These waves travel in the empty spaces between particles until their energy is absorbed by a particle. Would radiation pass through a solid or a gas more easily? List 3 examples of heat radiation. Heat Heat is the thermal energy that is transferred from particles at a higher temperature to particles at a lower temperature Can you control heat flow? An INSULATOR is a material in which heat flows slowly Good Insulators: plastic, wood, air, fiberglass Materials that arent good insulators are CONDUCTORS. Heat flows quickly through a conductor. Good Conductors: metals What if there is no material? There is no conduction if there is no matter. A vacuum (empty space) is a perfect insulator because very little heat transfer can take place. We use vacuum insulators and air insulators all the time. List some examples. How is the water inside being heated?