Protons for Breakfast
Heat
Week 3
November 2014
In the event of
of…
an attack of giant hens…
How it all fits together…
Electricity
Atoms
Electromagnetic
waves
Heat
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
Key fact to remember…
• 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
Let us embark on a
temperature excursion…
Room Temperature
• Let’s start out at room temperature…
Room Temperature
(about 20 C)
Brownian Motion…
Milk
Microscope Glass
Web-Cam
Brownian Motion…
Melting Ice…
• And then get a little bit colder…
Room Temperature
(about 20 ºC)
Melting Ice
(0 C)
Photo credit http://www.cepolina.com/freephoto/
Melting Ice…
Melting
Ice…
• What happens when an ice cube touches your hand?
Heat Transfer
Hot Object
Cold Object
What happens
when they
come closer?
Heat Transfer
What happens when
a fast moving atom
hits
a slow moving atom?
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
A short cold story…
Solid Carbon Dioxide
and the balloon
Liquid nitrogen
• Getting cold…
Solid CO2
(-79.2 C)
Melting Ice
(about 0 C)
Room Temperature
(about 20 C)
‘Dry ice’ - Solid Carbon Dioxide
• Carbon dioxide is unusual in that it transforms straight from the
solid state to the gaseous state
Solid CO2
Tie Balloon
Spoon
Balloon
‘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
Did you do your homework?
• The coldest
place on Earth?
The phases of matter…
Solids, liquids and gases
Solids, liquids and gases and plasmas
• Solids, liquids and gases are called ‘phases’ of matter…
Normal
melt evaporate
Solid
Solid
melt Liquid
evaporate
sublimate
Not so normal
Gas
Gas
Plasma
Plasma
A caricature of a solid
A caricature of a liquid
A caricature of a gas hitting a wall
A caricature of a plasma
-
+
-
+
Solids, liquids, and gases
Liquid nitrogen
• Getting cold…
Liquid nitrogen
• Getting cold…
Solid CO2
(-79.2 C)
Liquid Nitrogen
(about -196 C)
Melting Ice
(about 0 C)
Room Temperature
(about 20 C)
Another short cold story…
Liquid Nitrogen and the balloon
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
And its not just balloons
The magnetic properties of terbium…
Magnetic Atoms
As many electrons orbit
the atom in one sense
as in another
Some electron orbits
are unpaired
Axis of orbits
S
N
Atom
Magnetic
Atom
Representation
The effect of temperature
Low Temperature
High Temperature
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
Absolute Zero
(-273.15 C)
Solid CO2
(-79.2 C)
Liquid Nitrogen
(-196 C)
Room Temperature
(about 20 C)
Melting Ice
(0 C)
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
Absolute Temperature
kelvin
• Used by scientists - I won’t mention it again.
Absolute Zero Solid CO2
Room Temperature
(0 kelvin)
(193.4 kelvin) (about 295 kelvin)
Liquid Nitrogen
(77 kelvin)
Melting Ice
(273.15 kelvin)
And now let’s start getting warm
• Normal body temperature for all mammals is 37 °C…
Absolute
Zero
(-273.15 C)
Liquid Nitrogen
(about -196 C)
Solid CO2
(-79.2 C)
Melting Ice
(about 0 C)
Temperature of
Mammals
(about 37 C)
Room Temperature
(about 20 C)
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
And warmer still…
• Water boils at 100 °C…
Absolute
Zero
(-273.15 C)
Liquid Nitrogen
(about -196 C)
Solid CO2
(-79.2 C)
Melting Ice
(about 0 C)
Temperature of
Mammals
(about 37 C)
Room
Temperature
(about 20 C)
Water boils
100  C
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.
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
Hovercraft
Getting hotter…
Much hotter…
And how hot
is a candle
flame?
• Guess!
Gas
Liquid
Solid
Air
A paperclip’s nightmare…
The magnetic properties of iron…
The effect of temperature
Low Temperature
High Temperature
Comparing Iron and Terbium
• Increasing the random
motion of the iron atoms
destroys the magnetically
ordered state
Absolute Zero
(-273.15 C)
Liquid Nitrogen
(-196 C)
Room Temperature
(about 20 C)
Solid CO2
Water Boils
(-79.2 C)
(100 C)
Melting Ice
(0 C)
Body Temperature Magnetism of
Iron destroyed
(37 C)
(780 C)
Comparing Iron and Terbium
• Increasing the random motion of the iron atoms
destroys the magnetically ordered state
• Magnetism is a ‘low’ temperature phenomenon
Even when the ‘low’ temperature is quite high!
Terbium
Magnetism of Terbium destroyed around -100 ºC
Magnetic Non-magnetic
Magnetic Non-magnetic
Magnetism of Iron destroyed around 780 ºC
Iron
Getting hotter still…
• The hottest things in your house are your light bulbs!
They become white hot 2500 °C in a fraction of a second
Stars…
• The colour of a star
depends upon its
surface temperature
Picture Credit:Richard Powell
http://www.atlasoftheuniverse.com/me.html
Reminder…
And how does this link
to the first two weeks?
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
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
A word about frequency (1)
• 1 oscillation per second is called 1 hertz
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)
Electromagnetic spectrum
Infra Red
Radio & TV
Ultra
Violet
GammaRays
Microwaves
X-Rays
400 THz (Red)
1 101 102
1000 THz
(Blue)
103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Frequency (Hertz)
Visible light…
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
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.
Light from atoms in solids
• 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.
Infra Red Light…
Electromagnetic spectrum
Infra Red
Radio & TV
Ultra
Violet
GammaRays
Microwaves
X-Rays
2500 °C
800 °C
20 °C
1 101 102
103 104 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022
Frequency (Hertz)
Infra Red Light
from ‘constrained’ molecules…
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
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
Infra red light from unconstrained molecules
• Different types of molecular jiggling occur at different frequencies
Water H20
Carbon dioxide C02
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
How it all fits together…
Electricity
Atoms
Electromagnetic
waves
Heat
How it all fits together…
Homework?
Homework
Research:
Please find one fact about global warming
(Write it down on a piece of paper and I’ll collect
the facts at the start of the next session)
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!
Goodnight
• blog.protonsforbreakfast.org
This PowerPoint ™ presentation.
Links to other sites & resources
Me going on about things
See you next week
to discuss…
Global Warming!