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Protons for Breakfast Week 3: Heat November 2009.

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Presentation on theme: "Protons for Breakfast Week 3: Heat November 2009."— Presentation transcript:

1 Protons for Breakfast Week 3: Heat November 2009

2 In the event of an alarm…

3 PfB How it all fits together… Electromagnetic waves Atoms Heat Electricity

4 PfB Tonight’s talk Atoms and molecules are ceaselessly moving Temperature is a measure of how fast the atoms and molecules are moving Atoms and molecules are constantly emitting and absorbing electromagnetic waves The frequency of the waves emitted and absorbed depends on temperature

5 PfB Key fact to remember…

6 Atoms (2) There are VAST numbers of atoms in everything. –In just a handful of anything there are about the same number of atoms as there are grains of sand on all the beaches and deserts on Earth combined Photo Credit: ID =

7 PfB Let us embark on a temperature excursion…

8 PfB Room Temperature Let’s start out at room temperature…

9 PfB Melting Ice… And then get a little bit colder… Photo credit Room Temperature (about 20 ºC) Melting Ice (0 C)

10 PfB Melting Ice… What happens when an ice cube touches your hand? Melting Ice…

11 PfB Heat Transfer Hot ObjectCold Object What happens when they come closer?

12 PfB Heat Transfer What happens when a fast moving atom hits a slow moving atom?

13 PfB Why did you feel cold and wet? Water molecules in the ice speed up and escape the electrical attraction of their neighbours Causes change of state from solid to liquid Atoms and molecules in your hand slow down Changes the rate at which special cells to send electrical signals to your brain - interpreted as a ‘too cold’ message

14 PfB ‘Dry ice’ - Solid Carbon Dioxide Jolly chilly…

15 PfB A short cold story… Solid Carbon Dioxide and the balloon

16 PfB Liquid nitrogen Getting cold… Room Temperature (about 20  C) Melting Ice (about 0  C) Solid CO 2 (-79.2  C)

17 PfB ‘Dry ice’ - Solid Carbon Dioxide Carbon dioxide is unusual in that it transforms straight from the solid state to the gaseous state

18 PfB ‘Dry ice’ - Solid Carbon Dioxide That’s a million million! Stupendous numbers –Molecules travel around 500 metres per second: 1000 miles per hour –Every atom in the surface of the balloon is struck about times per second

19 PfB Did you do your homework? The coldest place on Earth?

20 PfB The phases of matter… Solids, liquids and gases

21 PfB A word about solids, liquids and gases Solids, liquids and gases are called ‘phases’ of matter… SolidGasLiquid evaporate Not so normal melt evaporatemelt Normal SolidGassublimate

22 PfB Solids A caricature of a solid

23 PfB Liquid A caricature of a liquid

24 PfB Liquid A caricature of a gas

25 PfB Solids, liquids, and gases

26 PfB Liquid nitrogen Getting cold…

27 PfB Liquid nitrogen Getting cold… Room Temperature (about 20  C) Melting Ice (about 0  C) Solid CO 2 (-79.2  C) Liquid Nitrogen (about -196  C)

28 PfB Another short cold story… Liquid Nitrogen and the balloon

29 PfB Liquid nitrogen (2) At 20  C molecules travel at around 500 metres per second: 1000 miles per hour At -196  C molecules travel at about half this speed: 250 metres per second: 500 miles an hour

30 PfB And its not just balloons… Magnetism (Part I)

31 PfB Liquid nitrogen (4) The magnetic properties of terbium…

32 PfB High TemperatureLow Temperature Liquid nitrogen (3) Slowing the random motion of the terbium atoms allows a magnetically ordered state to manifest itself A representation of an atom of terbium

33 PfB So what happens if you keep getting colder…? If the jiggling gets slower and slower then eventually atoms stop jiggling This corresponds to the lowest conceivable temperature Absolute zero

34 PfB Lord Kelvin (William Thompson) To measure is to know If you can not measure it, you can not improve it Heavier than air flying machines are impossible Radio has no future X-rays will prove to be a hoax

35 PfB Absolute Temperature kelvin Used by scientists - I won’t mention it again.

36 PfB And now let’s start getting warm Normal body temperature for all mammals is 37 °C… Temperature of Mammals (about 37  C) Room Temperature (about 20  C) Melting Ice (about 0  C) Solid CO 2 (-79.2  C) Liquid Nitrogen (about -196  C) Absolute Zero (  C)

37 PfB The Body Temperature of Animals AnimalTemperature (  C ) Range (  C ) Horse38.0  0.5 Dog38.2  1.0 Cat38.5  0.7 Whale37.0  ? Rat38.5  0.5 Guinea Pig38.2  1.0 Photo Credit

38 PfB And warmer still… Water boils at 100 °C… Temperature of Mammals (about 37  C) Room Temperature (about 20  C) Melting Ice (about 0  C) Solid CO 2 (-79.2  C) Liquid Nitrogen (about -196  C) Absolute Zero (  C) Water boils 100  C

39 PfB The Leidenfrost Effect Water boils at 100 °C… When it touches a very hot surface, it turns immediately to a vapour which causes droplets to float on a bed of vapour.

40 PfB Break time Activity Go forth, and be amused Take care. Liquid Nitrogen and solid CO 2 are cold and can give severe frostbite. Balloons Ice Cream Thermal Camera

41 PfB Getting hotter… Much hotter…

42 PfB And how hot is a candle flame? Guess!

43 PfB And how hot is a gas flame? Guess!

44 PfB A paperclip nightmare… Magnetism (Part II)

45 PfB Liquid nitrogen (4) The magnetic properties of iron…

46 PfB High TemperatureLow Temperature Liquid nitrogen (3) Speeding up the random motion of the iron atoms destroys the magnetically ordered state of iron A representation of an atom of iron

47 PfB Increasing the random motion of the iron atoms destroys the magnetically ordered state Comparing Iron and Terbium

48 PfB Magnetism is a ‘low’ temperature phenomenon –Even when the low temperature is quite high! Comparing Iron and Terbium Magnetism of Terbium destroyed around -100 ºC Magnetic Non-magnetic Magnetic Non-magnetic Terbium Iron Magnetism of Iron destroyed around 780 ºC

49 PfB The hottest things in your house are your light bulbs! –They become white hot 2500 °C in a fraction of a second Getting hotter still…

50 PfB The colour of a star depends upon its surface temperature Stars… Picture Credit:Richard Powell

51 PfB Reminder… And how does this link to last week…

52 PfB A word about frequency (1) 1 oscillation per second is called 1 hertz

53 PfB A word about frequency… oscillations per secondis called a… 1000 (a thousand) (10 3 ) kilohertz (kHz) (a million) (10 6 ) megahertz (MHz) (a billion) (10 9 ) gigahertz (GHz) (a trillion) (10 12 ) terahertz (THz) (a million billion) (10 15 ) petahertz (PHz)

54 PfB Microwaves From –0.8 GHz to –1000 GHz Radio & TV Infra Red Microwaves Gamma- Rays X-Rays Ultra Violet Frequency (Hertz) 1000 THz (Blue) 400 THz (Red) Electromagnetic spectrum

55 PfB Microwaves From –0.8 GHz to –1000 GHz Radio & TV Infra Red Microwaves Gamma- Rays X-Rays Ultra Violet Frequency (Hertz) Electromagnetic spectrum 2200 °C 800 °C 300 °C 20 °C

56 PfB Summary Heat Heat is the ceaseless disordered motions of atoms and molecules Temperature is a measure of the speed with which atoms and molecules move Atoms and molecules are electrical in their nature, and as they move they are constantly emitting and absorbing electromagnetic radiation

57 PfB Spectra Last week we saw that different sources of light have quite different spectra –Discrete (made of ‘lines’) –Continuous (Like a rainbow) We make light by simply ‘hitting’ an atom: hard –Strike it with an other atom –Strike it with an electron –‘Shake it’ with an electric wave

58 Lets remind ourselves about atoms (1) The internal structure of atoms Electrons ‘orbit’ around the outside of an atom very light possess a property called electric charge Nucleus occupies the centre very tiny and very heavy protons have a property called electric charge neutrons have no electric charge

59 Lets remind ourselves about atoms (2) Nuclei (+) attract electrons (-) until the atom as a whole is neutral The electrons repel each other –They try to get as far away from each other as they can, a –and as near to the nucleus as they can Electrons Electrons possess 1 unit of negative charge Nucleus protons possess 1 unit of positive charge neutrons have no electric charge

60 PfB Visible light…

61 PfB Light from atoms… If an atom or molecule is ‘unconstrained’ then When it is hit, it ‘rings’ like a bell Atoms ‘ring’ at their natural frequency: resonance Each type of atom vibrates in a characteristic manner.

62 PfB If an atom or molecule is ‘constrained’ then it cannot ‘ring’ clearly. The light which emerges has a mixture of all possible frequencies The balance of colours in the spectrum depends on how fast the atoms are jiggling – i.e. on temperature. Light from atoms in solids (1)

63 PfB Infra Red Light…

64 PfB

65 What happens if you knock a molecule? If a molecule is hit, the atoms within a molecule vibrate. Because atoms are thousands of times heavier than electrons they ‘ring’ with a much lower frequencies. The light given off is in the infra red range of the spectrum. H20H20

66 PfB Some molecules vibrating Different types of molecular jiggling occur at different frequencies

67 PfB Radio & TV Infra Red Microwaves Gamma- Rays X-Rays Ultra Violet Frequency (Hertz) Electromagnetic spectrum 2200 °C 800 °C 300 °C 20 °C

68 PfB Infra-Red light Objects at around ambient temperature emit infra-red light with a wavelength of about 0.01 mm. For example: –Our bodies –The Earth

69 PfB Infra-Red light We can see infra-red light using either –a normal video camera –a special ‘thermal’ camera

70 PfB Light from atoms in solids The filament of a normal light bulb is heated to about 2500 celsius to make it give off ‘white’ light When something is at about 800 celsius: its red hot When its colder, it gives off only infra-red light. We can’t ‘see’ this light but we can detect it.

71 PfB Summary Heat Heat is the ceaseless disordered motions of atoms and molecules Temperature is a measure of the speed with which atoms and molecules move Atoms and molecules are electrical in their nature, and as they move they are constantly emitting and absorbing electromagnetic radiation

72 PfB How it all fits together… Electromagnetic waves Atoms Heat Electricity

73 PfB How it all fits together…

74 PfB Homework?

75 PfB Homework Research: Please find one fact about global warming (Write it down on a piece of paper and I’ll collect the facts before the Global Warming session)

76 PfB One minute feedback Please write down one thing you understood this evening. Please write down one thing you didn’t understand.

77 On-line Resources –This PowerPoint ™ presentation. –Handouts as a pdf file blog.protonsforbreakfast.org –Me going on about things links.protonsforbreakfast.org –Links to other sites & resources

78 PfB See you next week to discuss… Global Warming! Goodnight


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