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Heat

Heat. How can we use this topic?. Fire Inspector Safety Inspector Thermal Engineer Researcher Welder Barista Renewable Energy Engineer Energy Analyst. S2 Science Heat. New Learning

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Heat

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  1. Heat

  2. How can we use this topic? • Fire Inspector • Safety Inspector • Thermal Engineer • Researcher • Welder • Barista • Renewable Energy Engineer • Energy Analyst

  3. S2 ScienceHeat New Learning I can use my knowledge of the different ways in which heat is transferred between hot and cold objects and the thermal conductivity of materials to improve energy efficiency in buildings or other systems. SCN 3-04a • Revision • By considering examples where energy is conserved, I can identify the energy source, how it is transferred and ways of reducing wasted energy • . • SCN 2-04a

  4. Starter • What is heat? • Think, pair, share (2 mins) • How do we get heat? • Where does it come from?

  5. Lesson 1: Cooling down • What is heat and what is temperature? • How does heat move from one place to another? • What cools more quickly – a hot or a cold object? • What cools more quickly – a large or a small object?

  6. What is temperature? • Temperature tells us how hot an object is • Temperature is measured in degrees Celsius oC • A Thermometer measures Temperature Anders Celsius(1701 – 1744)

  7. Heatenergy • Heat (like light) is a form of ENERGY • All energy is measured in Joules (named after James Joule) • A joulemetermeasures energy. What is heat? James Joule(1818 – 1889)

  8. Heat What is cooling? When a substance loses heat energy, it cools down and its temperature drops. Hot objects lose heat energy to colder surroundings.

  9. 100 Temperature OC Time in minutes

  10. Cooling Curves • Eventually, a hot object will cool down to the same temperature as its surroundings. • This is usually room temperature. • Comfortable room temperature is usually around 20oC • So, a hot object will only cool down to this temperature.

  11. Cooling Curve - explanation Heat removed from source Cooling most quickly around here Cooling is slowing down as it approaches room temperature Temperature Substance has reached room temperature Room temperature Time

  12. Lesson 1: Cooling down • Heat is a form of ENERGY • Heat always moves from a hot place to a cooler place. • A cup of hot coffee will cool down to room temperature. • When an object is much hotter than its surrounding it will cool down faster • Houses lose more heat in the winter. • A large cup will cool down more slowly than a small one. Hot Heat Cold

  13. Lesson 2: Conduction • How does heat move through solids? • What is a conductor of heat? • What kind of substances are the best conductors? • What is an insulator of heat? • What kind of substances are the best insulators?

  14. Starter • Imagine you are in your bedroom • Write down the sources of heat in your room.

  15. HEAT CAN MOVE BY 3 METHODSCONDUCTION, CONVECTION AND RADIATION

  16. Heat Transfer by Conduction • Conductionoccurs because the heat energy can pass from one particle to the next. It is most common in solids, where the particles are tightly packed together

  17. What are Conductors and Insulators? • A good conductor of heat lets the heat energy travel through it easily • A poor conductor of heat (Insulator) does not let heat energy travel though it easily. • Metals are very good conductors of heat • Non metals (eg Glass, wood plastic) are poor conductors of heat They are insulators

  18. Heat Transfer by Conduction • Why is the saucepan made of metal but the handle is made of plastic? • The pan needs to conduct heat to the cooking food but the handle must insulate to prevent heat passing to the hand.

  19. Plastic spoon or • Metal spoon Cold hand Cold hand Plastic spoon Insulator Metal spoon Conductor Hot soup

  20. Experiment 1 :- Why does metal feel colder than wood, if they are both at the same temperature? Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

  21. Lesson 2 Experiment 2

  22. Lesson 2 Experiment 3

  23. Copy and Complete

  24. Conduction Video • https://www.youtube.com/watch?v=wV7gzcKegdU

  25. Lesson 2: Conduction • Heat moves through some solids by conduction • Substances that allow heat to move easily through them are called conductors. • Metals are good conductors of heat. • Substances that do not allow heat to move through them easily are called insulators. • Air, plastics and wood are insulators. • Heat energy is conducted from the hot end of an object to the cold end

  26. Lesson 3 - Starter • Which substances are good conductors? • What do we call a substance that does not let heat travel through it? • Give an 2 examples of these substances.

  27. Lesson 3: Convection • How does heat travel in gases and liquids? • When parts of a gas are heated how, how does the gas move? • When parts of a gas are cooled – how does it move? • What is a convection current?

  28. Water movement Cools at the surface Convection current Hot water rises Cooler water sinks

  29. Convection in a Gas (air) Convection\Convection, chimney, hot air balloon.wmv

  30. Heat energy can also move through fluids (liquids & gases) by Convection. • Liquids and gases are called fluids because their particles are free to move (flow). • Hot fluids moves UP because it is less dense than cold fluids. • When the hot fluids move, they are replaced with colder fluids. Heat Transfer by Convection

  31. The movement of these particles is • called a convection current. • We usually cannot see the particles • move but the following experiments • allow us to see convection currents in a • fluid easily. Heat Transfer by Convection

  32. Convection in a liquid (water)

  33. Convection current in a liquid

  34. Why is it windy at the seaside?

  35. Cold air sinks Where is the freezer compartment put in a fridge? Freezer compartment It is warmer at the bottom, so this warmer air rises and a convection current is set up. It is put at the top, because cool air sinks, so it cools the food on the way down.

  36. YouTube: Demonstration of convection current in tubing.https://www.youtube.com/watch?v=0mUU69ParFM

  37. What can we learn from the video? • Wisc-online animation: Convection • BBCclip : Convection and Insulation • Clip on Convection chimney, hot air balloon • Cold water falls • Hot water rises

  38. Lesson 3 Convection Examples

  39. Convection current • Cold water falls • Hot water rises Freezer

  40. Convection in a room • Where’s the warmest place? • The radiator heats air which forms a current as shown in the picture: • Warmer air rises; • Cooler air falls. • The ceiling is the warmest place!

  41. Convection currents at the seaside • Through the day the land becomes warmer than the sea • At night the land becomes colder than the sea.

  42. Lesson 3: Convection • Convection happens in liquids and gases • As a gas is heated, it warms, expands, and rises because it is less dense than the cooler surrounding gas. • Likewise, when a liquid cools, it becomes more dense and falls. • As the gas or liquid warms and rises, or cools and falls, it creates a convection current.

  43. Lesson 4 - Starter • Draw a diagram showing what happens in Convection • Label the diagram

  44. Lesson 4: Radiation • What are some uses of heat radiation? • What can heat radiation travel through? • What is the 3rd way heat can travel? • What is heat radiation?

  45. Lesson 4: What is heat radiation • Heat can travel by invisible rays. • They travel in straight lines. • Our skin can sense these rays. Use your palms to feel the heat of a far away hot object. • These rays are called INFRA RED rays, because they are beyond red (so invisible). • Wisc-online animation: radiation

  46. Aluminium fire fighting suit • Heat rays are reflected by shiny surfaces. • Aluminium suits are used by firefighters to combat heat rays from fires. • YouTube video: Aluminium firefighting suit

  47. Thermal imaging • Thermal images are made by special camera sensitive to infra red radiation (heat rays). • The colours you see are not real. • The scale shows the colour matched against temperature. • YouTube: Man throwing hot and cold balloons

  48. Heat radiation in cooking • Infra red radiation cooks our food: • YouTube video: Char-Broil TRUinfrared

  49. All warm objects give off infra red radiation (IR). • That includes warm objects in space. • Infrared can travel through the vacuum of space. • Astronomers use IR telescopes to look at stars, dust clouds, comets and asteroids. • Now examine the following IR space photographs:

  50. Constellation Orion Visible Light

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