Set up Camera Person Conduction Examples: Boys vs. Girls – Who can melt the ice cube fastest? Ice Blocks - One a conductor, one an insulator. Conduct - draws heat away. Conducts heat from the room, causing the ice cube to melt. Boiling water in a paper cup: Burn paper cup 1. Fill cup 2 with water. Put under flame. Water is a good conductor. Conducts heat away from the paper cup before it has time to burn. Heating a balloon: With and without water. Getting out of bed in the morning with bare feet: Choice A carpet. Choice B. tile. Which one? They are both the same temperature. Tile conducts the heat - draws heat out of your foot faster….so it feels colder. So why do we curl our toes when we're walking around? Less surface area to conduct heat away from out body. Conductometer: Run under hot water Ball and Ring Demo (with student) Tabletop Vs. Metal Faucet: One feels warm, one feels cold. But both are the same temperature. Which took he thermal energy away? Therefore it is a good conductor. Beaker of hot water. Take a glass mercury thermometer, dunk it in and remove. What happens? Mercury goes DOWN. (Glass expands) Wax on metal spokes - Conducts heat at different rates Bi-metallic Strip Thermometer in hot water for a brief moment - what happens? reading will drop. Because thermal expansion briefly causes the glass to expand, allowing it to go down. But once, the glass conducts the heat TO the mercury, that's when thermal expansion will cause it to rise. (That's why you need time to take a thermometer reading. ) Cooking a potato fast Convection Demonstrations: Why do we say that hot air rises? It doesn't - it just has to do with densities. Cold air is more dense that warm air. So cold air goes down, warm air rises causing a convection current. Seeing Convection with pepper in beaker Convections Glass Tube Seeing Convection Current In projector Popcorn Maker – Convection. Compare to putting it into a pan? What about a microwave? Hand Boilers – Heat form hand, expands air inside, difference in pressures allow the liquid to rise. Heated flask with food coloring put into larger container of water: https://www.youtube.com/watch?v=WEDUtS0IMws Radiation: Clarification on What Radiation is: https://www.youtube.com/watch?v=Zw0pHT47AAU Heat transfer without "stuff" Transfers as a wave. Sun – travels through empty space…eliminate conduction, eliminate convection (no air in space) so there must be another kind. Light a lightbulb - feel the warmth right away, but the bulb isn't hot. Campfire – Feel the “burn” - You can tell the difference between that and a breeze of warmed up air brushing past you. Red Hot Glowing Oven Coils – Radiation Radiometer – only spins this direction. Why?
