Agenda for 3/3/17 Heat Energy Notes Heat Problems HW – keep working on PE/KE Lab type up

* 07/16/96 Heat Energy *

Temperature Temperature - * 07/16/96 Temperature Temperature - measure of the average KE of the particles in a sample of matter *

Temperature Conversions * 07/16/96 Temperature Conversions oC to oF: oF = 9/5oC + 32 oF to oC: oC = 5/9(oF – 32) oC to K: K = oC + 273 K to oC: oC = K – 273 *

Thermal Energy Thermal Energy - * 07/16/96 Thermal Energy Thermal Energy - the total energy (KE and PE) of the particles in a material depends on temperature, mass, and type of substance *

Thermal Energy A B Which beaker of water has more thermal energy? * 07/16/96 Thermal Energy Which beaker of water has more thermal energy? B - same temperature, more mass 200 mL 80ºC A 400 mL B *

* 07/16/96 Heat Transfer Heat - thermal energy that flows from a warmer material to a cooler material Heat is always transferred from hot to cold Ex. A warm soda with ice in it gets cooler (loses heat) because the heat from the soda is being transferred to the ice, causing ice to melt *

Heat Transfer A B Why does A feel hot and B feel cold? * 07/16/96 Heat Transfer Why does A feel hot and B feel cold? Heat flows from A to your hand = hot. Heat flows from your hand to B = cold. 80ºC A 10ºC B *

Heat Transfer Heat is transferred in 3 different ways – 1) conduction * 07/16/96 Heat Transfer Heat is transferred in 3 different ways – 1) conduction 2) convection 3) radiation *

* 07/16/96 Specific Heat Specific Heat (Cp) - the ability of matter to GAIN or LOSE heat Each object has its own characteristic specific heat These values are the amount of heat needed to raise the temperature of 1 g of water by 1°C Compare the temperature of the metal part of your desk to your notebook. Which feels cooler? *

Heat Transfer Which sample will take longer to heat to 100°C? 50 g Al * 07/16/96 Heat Transfer Which sample will take longer to heat to 100°C? 50 g Al 50 g Cu Al - It has a higher specific heat. Al will also take longer to cool down. *

Q = m  T  Cp Heat Problems Q: heat (Cal)  units for heat * 07/16/96 Heat Problems Q = m  T  Cp Q: heat (Cal)  units for heat m: mass (g) T: change in temperature (°C) Cp: specific heat (Cal/g.oC) – Q = heat loss + Q = heat gain T = Tf - Ti *

Heat Problems Q = 32 x (20 - 60) x 0.0564 Q = 32 x -40 x 0.0564 * 07/16/96 Heat Problems A 32-g silver spoon cools from 60°C to 20°C. How much heat is lost by the spoon? Q = m x (final temp – initial temp) x Specific Heat Q = 32 x (20 - 60) x 0.0564 Q = 32 x -40 x 0.0564 Q = -72.192 Cal *

Heat Problems How many calories of heat must flow into 150 grams of water at 0° C to raise its temperature to 25° C? Q = m x (final temp – initial temp) x Specific Heat Q = 150 x (25 – 0) x 1.00 Q = 150 x 25 x 1 3,750 Calories

Conduction The transfer of heat by direct contact between objects or particles. Occurs best in solids Transferred until equal

Convection Heat transferred by the movement of molecules within a substance. Movement occurs from warmer areas to cooler areas.

Convection Currents - The movement of a substance that is caused by differences in temperature and density. EXAMPLES: wind, boiling water

Radiation Heat transferred through space. Transferred in all directions. No contact required! Dark or dull objects absorb more than light or shiny objects do. EXAMPLE: The sun’s rays causing a sunburn.

Agenda for 3/6/15 Go over quiz Finish Heat Energy Notes Heat Energy Problems No HW

Agenda for 3/9/15 Ticket in the Door Go over heat problems from Friday Transfer of Heat Lab HW – Finish Lab (if not completed in class) and More Heat Problems Worksheet