1. Transferring Thermal Energy Chapter 9 Section 3a

2. Heat Transfer Heat flows from hot to cold. Heat flows from hot to cold. If you hold something cold, heat flows from hand to object. If you hold something cold, heat flows from hand to object. If you hold something hot, heat flows from object to hand If you hold something hot, heat flows from object to hand Conduction- transfer of thermal energy through matter by the direct contact of particles Conduction- transfer of thermal energy through matter by the direct contact of particles Occurs because particles are in constant motion Occurs because particles are in constant motion KE transferred as particles collide KE transferred as particles collide

3. http://www.physchem.co.za/Heat/Transfer.htm# Conduction http://www.physchem.co.za/Heat/Transfer.htm# Conduction

4. Conduction Heating of metal pan- Heating of metal pan- Particles in handle of pan move slowly Particles in handle of pan move slowly Fast moving particles from the bottom bump into slower particles and speed them up Fast moving particles from the bottom bump into slower particles and speed them up Occurs until all particles move the same speed Occurs until all particles move the same speed Conduction works best in solids- especially metals- because particles are close together Conduction works best in solids- especially metals- because particles are close together

5. Conduction and Convection Metals- good conductors-because electrons move easily & transfer KE to nearby particles Metals- good conductors-because electrons move easily & transfer KE to nearby particles Fluid- any materials that flows Fluid- any materials that flows Convection- transfer of energy in a fluid by the movement of heated particles Convection- transfer of energy in a fluid by the movement of heated particles Convection currents transfer heat from warmer to cooler parts of a fluid. Convection currents transfer heat from warmer to cooler parts of a fluid. Convection vs. Conduction- Convection vs. Conduction- Conduction involves collisions and transfers of energy. Conduction involves collisions and transfers of energy. Convection involves movement of the energetic particles from one location to another Convection involves movement of the energetic particles from one location to another

7. Convection Convection- results in changes in density Convection- results in changes in density As particles move faster, they get farther apart As particles move faster, they get farther apart Fluid expands as temperature increases Fluid expands as temperature increases Larger volume = smaller density Larger volume = smaller density Decreasing density results in the rise of the warmer fluid Decreasing density results in the rise of the warmer fluid Lava Lamp- Lava Lamp- Cool oil = dense = sits on the bottom Cool oil = dense = sits on the bottom Warmer oil = less dense than alcohol & rises Warmer oil = less dense than alcohol & rises As it rises, it loses energy through conduction As it rises, it loses energy through conduction Causes decrease in density = sinking Causes decrease in density = sinking

8. When oil is cool When oil is cool Oil is warm, so it rises Oil is warm, so it rises Oil starts to lose heat by conduction and falls

9. Convection Currents Currents in which warm portions of the fluid move through the substance- convection Currents in which warm portions of the fluid move through the substance- convection The warm portions transfer energy to the cool section through conduction The warm portions transfer energy to the cool section through conduction

10. Heat Transfer on Earth At equator- earth experiences the most heat from the sun. At equator- earth experiences the most heat from the sun. Result: evaporation of water and large accumulations of clouds. Result: evaporation of water and large accumulations of clouds. As the water vapor rises, it cools and condenses, forming rain As the water vapor rises, it cools and condenses, forming rain After the rain = dry air After the rain = dry air Dry air causes moisture to evaporate, drying out the ground – causes desert Dry air causes moisture to evaporate, drying out the ground – causes desert Convection currents create deserts and rain forests over different regions of Earth Convection currents create deserts and rain forests over different regions of Earth