protons for breakfast week 3: heat march 2011. in the event of an alarm…
Post on 30-Dec-2015
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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
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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: http://www.morguefile.com ID = 104101
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Melting Ice…
• And then get a little bit colder…
Photo credit http://www.cepolina.com/freephoto/
Room Temperature
(about 20 ºC)
Melting Ice
(0 C)
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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
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Liquid nitrogen
• Getting cold…
Room Temperature (about 20 C)Melting Ice
(about 0 C)
Solid CO2
(-79.2 C)
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‘Dry ice’ - Solid Carbon Dioxide
• Carbon dioxide is unusual in that it transforms straight from the solid state to the gaseous state
Balloon
Spoon
Solid CO2 Tie Balloon
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‘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 1012 times per second
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A word about solids, liquids and gases
• Solids, liquids and gases are called ‘phases’ of matter…
Solid GasLiquidevaporate
Not so normal
melt
evaporatemeltNormal
Solid Gassublimate
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Liquid nitrogen
• Getting cold…
Room Temperature (about 20 C)Melting Ice
(about 0 C)
Solid CO2
(-79.2 C)
Liquid Nitrogen (about -196 C)
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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
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High Temperature Low 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
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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
Room Temperature (about 20 C)
Melting Ice (0 C)
Solid CO2
(-79.2 C)
Liquid Nitrogen
(-196 C)
Absolute Zero
(-273.15 C)
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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
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Absolute Temperaturekelvin
• Used by scientists - I won’t mention it again.
Room Temperature (about 295 kelvin)
Melting Ice (273.15 kelvin)
Solid CO2
(193.4 kelvin)
Liquid Nitrogen
(77 kelvin)
Absolute Zero
(0 kelvin)
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And now let’s start getting warm
• Normal body temperature for all mammals is 37 °C…
Temperature ofMammals
(about 37 C)
Room Temperature (about 20 C)Melting Ice
(about 0 C)
Solid CO2
(-79.2 C)
Liquid Nitrogen (about -196 C)
Absolute Zero
(-273.15 C)
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The Body Temperature of Animals
Animal Temperature
(C )
Range
(C )
Horse 38.0 0.5
Dog 38.2 1.0
Cat 38.5 0.7
Whale 37.0 ?
Rat 38.5 0.5
Guinea Pig 38.2 1.0
Photo Credit http://www.graficworld.it/public/photos/cat-dog-19.jpg
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And warmer still…
• Water boils at 100 °C…
Temperature ofMammals
(about 37 C)
Room Temperature (about 20 C)Melting Ice
(about 0 C)
Solid CO2
(-79.2 C)
Liquid Nitrogen (about -196 C)
Absolute Zero
(-273.15 C)
Water boils
100 C
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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.
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Break time Activity
• Go forth, and be amused• Take care. Liquid Nitrogen and solid
CO2 are cold and can give severe frostbite.
• Balloons• Ice Cream• Thermal Camera
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High Temperature Low 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
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• Increasing the random motion of the iron atoms destroys the magnetically ordered state
Comparing Iron and Terbium
Room Temperature (about 20 C)
Melting Ice (0 C)
Solid CO2
(-79.2 C)
Liquid Nitrogen
(-196 C)
Absolute Zero
(-273.15 C)
Body Temperature (37 C)
Water Boils (100 C)
Magnetism of Iron destroyed
(780 C)
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• 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
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• 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…
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• The colour of a star depends upon its surface temperature
Stars…
Picture Credit:Richard Powellhttp://www.atlasoftheuniverse.com/me.html
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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
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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
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A word about frequency…
oscillations per second is called a…
1000(a thousand) (103)
kilohertz (kHz)
1000000 (a million) (106)
megahertz (MHz)
1000000000 (a billion) (109)
gigahertz (GHz)
1000000000000 (a trillion) (1012)
terahertz (THz)
1000000000000000 (a million billion) (1015)
petahertz (PHz)
PfB1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Radio & TVInfra Red
Microwaves
Gamma-Rays
X-Rays
Ultra Violet
Frequency (Hertz)
1000 THz (Blue)400 THz (Red)
Electromagnetic spectrum
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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
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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.
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• 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)
PfB1 101 102 103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Radio & TVInfra Red
Microwaves
Gamma-Rays
X-Rays
Ultra Violet
Frequency (Hertz)
Electromagnetic spectrum
2500 °C
800 °C
20 °C
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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
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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.
H20
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Infra red light from unconstrained molecules
• Different types of molecular jiggling occur at different frequencies
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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
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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)
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One minute feedback
• On the back of your handouts!• Rip off the last sheet• Please write down what is in on your mind RIGHT NOW!
– A question? OK– A comment? OK– A surprising thought in your mind? I’d love to hear it!
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On-line Resources
• www.protonsforbreakfast.org –This PowerPoint ™ presentation.–Handouts as a pdf file
• blog.protonsforbreakfast.org –Me going on about things–Links
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