7.3.5PresentationAbout_Heat_Science.pptx

presentation about heat

1. HEAT module 5 [unit 3] RETOOLING OF GRADES 7, 8 & 9 SCIENCE TEACHERS APRIL 13-15, 2015 Jeffrey Policarpio

2. The Cone of Experience Degree of involvement Verbally receiving } } Visually receiving Saying } } Saying & doing What we remember 10 % 20 % 30 % { 50 % { 70 % { 90 %

3. Heat and Temperature Concept of “Thermal Energy” and Heat Thermometer as a measuring device for temperature Mechanisms of Heat Transfer Conduction Convection Radiation

4. Setting the Scope Grade 7 - 9

5. Heat and Temperature Concept of “Thermal Energy” and Heat Thermometer as a measuring device for temperature Mechanisms of Heat Transfer Conduction Convection Radiation infers the conditions necessary for heat transfer to occur explains different modes of heat transfer in terms of the movement of particles identifies good and poor conductors of heat and describe their specific uses TOPICS LEARNING COMPETENCIES

6. PATI BA NAMAN HEAT PINAG-AARALAN? PAG HINDI KO TO NAINTINDIHAN, WLA KANG PBB MR. SEDUTAN !

7. Mechanism of Heat Transfer 1. Conduction 2. Convection 3. Radiation

8. Conduction When you heat a metal strip at one end, the heat travels to the other end. As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction

9. Metals has free electrons

10. Metals are different The outer e_______ for metal atoms drift, and are free to move. When the metal is heated, this ‘Sea of electrons’ gain k_____ energy and transfer it throughout the metal. Insulators, such as w___ and p____, do not have this ‘Sea of electrons’ which is why they do not conduct heat as well as metals. lectrons inetic ood lastic

11. Why does metal feel colder than wood, if they are both at the same temperature? Believe it or not, they are not colder! Metal is a conductor, wood is an insulator. The metal conducts the heat away from your hands, the wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal. Check Up!

12. 2 TYPES OF MATERIALS based on its ability to conduct heat. Some materials are good thermal conductors , others are insulators . 98º 75º 98º 75º Wood is an insulator Tile is a conductor Tile floor feels colder than wood floor

13. Conductor Something that allows thermal energy to pass easily Metal Water Glass

14. Air is a Poor Conductor Can safely put your hand in an hot oven. Metal is good conductor so you need oven mitt to touch it (cloth is poor conductor). Because air is such a poor conductor, some pizza ovens don’t have a door.

15. Check Up! Question Explain why “firewalkers” can walk safely across a bed of red-hot coals in bare feet.

16. Check Up! Answer Because the rate of heat transfer is slow, because coals are not very good conductors. If they walk fast enough, there is only a small amount of heat transferred to their feet, and they do not burn.

17. Insulator Something that does NOT allow thermal energy to pass easily.

18. Insulator

19. Experiment 1 (Conduction) METALS ARE GOOD CONDUCTORS OF HEAT - Description : A piece of paper, with a metal coin placed on top of it, is placed above a candle flame. The metal conducts the heat from the flame away, preventing the paper from charring at the location of the metal coin. -The scientific principle which was illustrated in this experiment was that metal is a good conductor of heat. -This demonstration is effective in demonstrating the scientific principle because a pattern of the coin is left on the paper, proving that only the place where the coin was placed remained uncharred. http://www.johnny-lin.com/teach/phsc101/groups/heat.html

20. Experiment 2 (Conduction) CONDUCTION WITH A METAL GAUZE - Description : A metal gauze is held in a flame, but the flame does not come through the screen because the heat is conducted away from the flame by the wires. -The scientific principle illustrated by this experiment is that metal conducts heat. -This experiment is effective because you see that the flame only burns above the wire. The wire conducts the heat away, thus preventing the gas below the screen from reaching its kindling temperature http://www.johnny-lin.com/teach/phsc101/groups/heat.html

21. Heating fluids What happens to the particles in a liquid or a gas when you heat them? The particles spread out and become less dense. This effects fluid movement. What is a fluid? A liquid or gas.

22. Fluid movement Cooler, more d____, fluids sink through w_____, less dense fluids. In effect warmer liquids and gases r___ up. Cooler liquids and gases s___. ense armer ise ink

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

24. Experiment (Convection) HEAT IS TRANSFERRED BY CONVECTION IN LIQUIDS – Description : Fill a jar with water. Drop paper particles and give it time to settle to the bottom. Once settled, place a Bunsen burner underneath the jar and let the water boil. Observe the motion of the paper particles. -The scientific principle illustrated by this experiment is that heat is transmitted by convection, which is heat transfer by the motion of the fluid by currents. -This experiment is effective because the paper particles are settled on the bottom before boiling. While the jar of water is heated, the paper particles show the path of the currents. This shows that heat is transmitted in fluids by currents. http://www.johnny-lin.com/teach/phsc101/groups/heat.html

25. CONVECTION Convection is the transfer of heat by the actual movement of the warmed matter. Heat leaves the coffee cup as the currents of steam and air rise. Consider this: convection is responsible for making macaroni rise and fall in a pot of heated water. The warmer portions of the water are less dense and therefore, they rise. Meanwhile, the cooler portions of the water fall because they are denser.

26. Experiment (Convection) Very HOT Warm Shadows reveal rising air currents of hot air. Rising hot air above a candle carries most of the heat generated by the burning flame.

27. Experiment (Convection) Candle stays light until the partition in the tube is removed. Why? Partition allows hot air to rise, drawing in cold air (with fresh oxygen) to fuel the candle flame. Without the partition, turbulence impedes the inflow and outflow. Convection is disrupted because tube is narrow.

28. Convection in air Light the candle & hold a piece of smoking paper on the other side of the cardboard. note smoke's movement

29. When air is heated, air expands, rises & is replaced by cold air from above.  convection current Convection current

30. Convection and particle motion When a fluid is warmed, the fluid particles move faster  warm fluid expands  less dense than surrounding cold fluid  warm fluid rises  cool fluid from the top moves down to replace warm fluid  convection current

31. Application Convection oven has a fan to enhance the circulation of the air, increasing the transfer of heat.

32. Application In Chinese herbal tea shops , bowls of herbal tea are usually covered by glass plates. Why do the shop owners need to do this?

33. Application Some freezers at supermarkets do not have doors. This is just opposite to what herbal tea shops do. What could be the reason?

34. Have you noticed... immersion heater is fixed near the bottom Application Air-conditioner is usually installed high on the wall

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

36. This results in a convection current . W arm air is taken in by the a ir - conditioner & cooled. Convection current An air-conditioner gives out cold air which falls. This pushes the warm air up . Why air-conditioners are usually set up high on the wall?

37. In a fire, why should you crawl close to the floor in a smoke-filled room? Smoke is warmer than the surrounding air. It rises & its places would be replaced by the surrounding cooler air. Smoke is toxic . We should crawl close to the floor to prevent smoke inhalation . Why crawl on ground during a fire?

38. Examples of convection Shape of candle flame hot air rises Fire or flames always point upwards ... since convection current flows upwards

39. Why is it windy at the seaside?

40. Land and sea breezes over the coast in the summer are caused by convection current. Examples of convection Wind and sea breezes

41. Examples of convection During the day, the Sun heats up the land more quickly than the sea. Warm air rises cool air blows in from the sea to replace it wind warm air expands warm air cools Wind and sea breezes

42. Why are boilers placed beneath hot water tanks in people’s homes? Hot water rises. So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water. Why does hot air rise and cold air sink? Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air. Check Up!

43. RADIATION Radiation is the process in which energy is transferred by means of electromagnetic waves.

44. Radiation Light has many different wavelengths, most of which are not visible to the eye. All light carries energy, thus transfers heat. Heat Lamp Highly reflective fire proximity suits

45. 7/30/2015 46 Electromagnetic radiation

46. When (EM Waves) light rays hit a material, the molecules in that material move faster.

47. How does heat energy get from the Sun to the Earth? There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection. ? RADIATION

48. Heat-Ray The “heat-ray” first appeared in science fiction as the Martian weapon in H.G. Wells’ classic novel, War of the Worlds (1898). http://www.youtube.com/watch?v=gsXnK0ouTL8 War of the Worlds (1953) Mars Attacks! (1997) High powered lasers are similar to H.G. Wells’ heat-ray.

49. Freeze-Ray There’s no current technology to create a ray that removes energy from an object. http://www.youtube.com/watch?v=TNjTW8ZBkuI 1968 Batman cartoon Batman and Robin (1997)

50. Emission of Radiant Energy All objects radiate light; higher the temperature the higher the light’s frequency. At room temperature the radiated light is at frequencies too low for our eyes to see. Special cameras are sensitive to this infrared radiation. Attics in this house were kept warm for growing marijuana. 98º 75º

51. Predator (1987) Heat vision made the Predator a deadly adversary.

52. Demo : Infrared Light Digital cameras, such as in cell phones, are sensitive to infrared light, such as from a remote control or any hot object. Microwave Transmitter Microwave Receiver

53. Emission experiment Four containers were filled with warm water. Which container would have the warmest water after ten minutes? Shiny metal Dull metal Dull black Shiny black The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation. shiny metal radiation dull black emitting

54. Absorption experiment Four containers were placed equidistant from a heater. Which container would have the warmest water after ten minutes? The __________ container would be the warmest after ten minutes because its surface absorbs heat _______ the best. The _________ container would be the coolest because it is the poorest at __________ heat radiation. dull black radiation shiny metal absorbing Shiny metal Dull metal Dull black Shiny black

55. Experiment (Radiation)

56. Why are houses painted white in hot countries? White reflects heat radiation and keeps the house cooler. Why are shiny foil blankets wrapped around marathon runners at the end of a race? The shiny metal reflects the heat radiation from the runner back in, this stops the runner getting cold. Check Up!

57. Check Up! Question If heat transfers from hot to cold, and stops when the two objects reach the same temperature, explain why it is possible for the inside of your car to be hotter than the air outside on a hot summer day.

58. Check Up! Answer The greenhouse effect. Electromagnetic waves from the sun enter your car through the windows and are absorbed by the seats and other objects in the car. They then re-emit electromagnetic radiation of a different wavelength that cannot pass through glass. All of that energy is therefore trapped inside the car, causing the temperature to rise.

59. Applications of the 3 M.H.T

60. Applications of the 3 M.H.T

61. The Mayonnaise Jar A professor stood before his philosophy class, with some unusual items in front of him on the desk.

62. The Mayonnaise Jar When the class began, he picked up a very large and empty mayonnaise jar and proceeded to fill it with golf balls. He then asked the students if the jar was full. They agreed that it was.

63. The Mayonnaise Jar The professor then picked up a box of pebbles and poured them into the jar. He shook the jar lightly and the pebbles rolled into the small gaps between the golf balls. He asked the students again if the jar was full, and they agreed that it was.

64. The Mayonnaise Jar Now the professor picked up a small box of sand and poured it into the jar. Of course, the sand filled up all the remaining gaps between the golfballs and the pebbles. Once again he asked the students if the jar was full, and the response was a unanimous ‘yes.’

65. The Mayonnaise Jar Now the professor produced two glasses of white wine from under the table and poured their contents into the jar, filling the remaining air pockets in the sand . The students laughed. When the laughter subsided, the professor said:  ‘Now imagine that this jar represents your life:

66. The Mayonnaise Jar The golf balls  are the important things – family, children, friends, favourite passions and your health. These are the things that, if everything else were lost and only they remained, your life would still be full. The pebbles  are the other things that matter like, your job, house, and car. The sand  is everything else — the small stuff.’

67. The Mayonnaise Jar The professor continued:  'The moral of my story is this: it’s important to get these things in your life in the right order. Here’s why :

68. The Mayonnaise Jar If you put the sand into the jar first, there won’t be any room left for the pebbles or the golf balls. The same goes for life. If you spend all your time and energy on the small stuff, you’ll never have room for the things that are important to you .

69. The Mayonnaise Jar So take care of the golf balls first, the things that really matter. The rest is just sand.

70. The Mayonnaise Jar So what the wine represented in the story? The wine just goes to show you that no matter how full your life may seem, there’s always room to share a glass or two with a friend .’ Source: http://briard.typepad.com/get_the_picture/2012/10/the-mayonnaise-jar-a-life-lesson-thatll-make-you-smile.html

71. Prepared by: Jeffrey Policarpio MA Scie . Ed. –Physics t soktok.blogspot.com Thank you… … for not asking questions!