ESCI 215
Chapter 5

In 1714 a German-Dutch scientist named
Gabriel Fahrenheit developed the first scale to
be used frequently
◦ Scale included: boiling, freezing, and zero points
◦ He selected an arbitrary “zero” point (32°F) so that
winter temperatures would still read as positive
values
◦ He selected the boiling point to be represented by
212°F, which was 180 degrees above the boiling
point


In 1742, Anders Celsius, a Swedish
astronomer invented the Celsius scale
Temperature scale with:
◦ Freezing point of water is the zero point (0°C)


100 degrees between the freezing and boiling
points
Works well with decimal systems, so was easy
for scientists to use





Lord Kelvin of England developed this scale
Absolute zero = the lowest possible
temperature (0K)
There are 273 degrees between absolute zero
and the freezing point (273K)
There are 100 degrees between the freezing
and boiling points (373K)
Using 0K to represent absolute zero meant
that no temperature could go below “zero”
using this scale

Heat and temperature are different
◦ Temperature scales measure temperature (not heat)
◦ Event 5-A shows the difference between
temperature and heat
 The nail and bolt have the same temperature, but the
bolt has more temperature
 See diagram page 72


Temperature – how hot or cold something;
measured in degrees (F, C, K)
Heat – a quantity of energy something has

Heat
◦ The energy a substance has due to motion of its
molecules
 Increased heat = increased molecular motion
 Decreased heat = decreased molecular motion
◦ Absolute zero = the point where all molecular
motion stops and a substance has no heat
 Scientists have never been able to get a substance to
this point

Heat is measured in calories, British thermal
units (Btu), or joules

Calorie – amount of heat needed to raise the
temperature of 1 gram of water by 1 degree
Celsius
◦ Common measurement

Btu – heat needed to raise 1 pound of water
by 1 degree Fahrenheit
◦ Used sometimes (i.e. furnace)

Joule –work done by 1 newton of force or
weight moving a body through 1 meter
◦ Used by scientists

1 gram of ice at 0°C or 1 gram of water at 0°C

1 gram of water at 100°C or 1 gram of steam at
100°C
◦ Water
◦ Steam

Why?
◦ When matter changes from a state of slower
molecular movement to a state of higher
molecular movement, heat is required
 Change from solid to liquid requires heat
 Heat is needed to melt ice or to change water to
steam
 Heat of fusion and heat of vaporization are
needed

1 calorie of heat increases temperature of 1 gram of
ice by 1 degree

If ice is -10C:
◦ How many calories are needed to get to 0C?
 10 calories
 melting point - but more heat is needed to change
state
 Heat of Fusion - change of state from solid to liquid
takes 80 calories
 How many calories are needed to get to 100C?
 100 calories
 Vaporization point – but more heat is needed to
change state
 Heat of Vaporization – change of state from liquid to
gas takes 540 calories
Figure 5.3 page 74 in Text

Where does the heat come from to change
the state of matter?
◦ It can come from anywhere




Air
Your body
Stove
Hot plate
◦ When you hold an ice cube, heat is taken from your
hand and used to melt the ice – leaving your hand
feeling cold
◦ When you step out of a shower, heat is taken from
your body and used to turn water into steam –
leaving you feeling cool


Event 5-B shows that there is no temperature
change unless there is a change in the
amount of heat present
Event 5-C demonstrates that heat of fusion is
what causes the ice to melt by taking heat
from the salt and using it to melt the ice
◦ This causes the temperature of the salt water to
drop below freezing
◦ This cooled water evaporates and forms frost on
the beaker


There are many sources of heat
Grouped into 4 categories:
Mechanical
Chemical
Electrical
Nuclear
Friction
Rearranging
molecules
Lights
Sun and stars
Bending
Flame
Toasters
Atomic
fission
Hammering
Water and
plaster
Heaters
Atomic fusion
Pressure
Sulfuric acid
and sugar
Stoves
Nuclear
power reactor
Table 5.2 page 77 of text

Event 5-D Shake heat into a Bottle
◦ Demonstrates a mechanical source of heat
◦ Sand hits top and bottom of bottle and this friction
causes heat
◦ Insulation around bottle is to make sure that the
heat is not coming from your hands

Event 5-E Wire Heater
◦ Demonstrates a mechanical source of heat
◦ Bending the wire causes heat to build at the bend

Some nails have adhesive on the shaft. This
adhesive does not do anything at room
temperature, but it melts when nailed into
wood. Why?
Conduction
Convection
Radiation
Definition
Transfer of heat
from one
molecule to
another
Transfer of heat
by movement of
fluids
Transfer of
energy by waves
through space
Examples
Silver spoon
Clothes
Iron
Cookware
Winds (weather)
Chimney draft
Boiling water
Sun’s heat
Heat lamp
Electric heater
Table 5.3 page 79 in text


Transfer of heat from 1 molecule to another
Event 5-G Ice Preservation Race
◦ Purpose – learn about movement of heat by conduction
 Could be used after learning about conduction to show
their understanding of the concept
 Could be used before learning about conduction to
have them explore ways to slow heat transfer
◦ 2 important rules:
 No refrigerators, ice, or outdoors
 Do not let ice touch anything that will soak up water –
water needs to be measured to find the winner
◦ Best results achieved when:
 Size of container is small – reduces the area to be
protected from heat
 Conductivity is decreased – tin conducts heat well so
need to insulate the ice cube from the tin

Good conductors
◦ Metals are usually the best conductors of heat (especially
copper, silver, aluminum)

Poor conductors
◦ Called insulators
◦ Glass, paper, wood, plastic rubber

Event 5-H Two toned paper shows the effects of
good and poor conductors
◦ Wood is a poor conductor of heat so the paper scorches
more than copper which conducts the heat away

Event 5-I Candle Snuffer shows a good conductor
◦ The candle goes out because the copper carries the heat
away from the candle, not because of oxygen loss



Transfer of heat by movement of fluids (gas
or liquid)
Convection current - Liquids expand and
become lighter when heated
Event 5-J The Mixed-Up Bottles shows a
convection current
◦ Hot water is less dense and rises
◦ Cold water is denser and sinks

Event 5-K The Circling Sawdust
shows the movement of water
Figure 3.7 page 80 in text

Event 5-L Does Air Move In or Out shows the
convection currents in air
◦ One window is open on the bottom and another is
open at the top to show the air movement in the
room
 Cold air enters the room through the lower opening
and hot air leaves the room through the higher
opening

Event 5-M Convection Tester #1 shows that
air rises when heated
◦ Air is heated by the bulb and rises, causing the coil
to spin (see figure 5.9 on page 81)

Energy travels, at the speed of sound, from a
source to an object; it travels through space
◦ Ex: heat from the sun

This energy is only converted to heat when it
hits a non-transparent object
◦ On a cold day the sun’s light heats up a window sill,
but the window’s glass is still cold

Substances vary in their ability to reflect and
absorb radiation
◦ Event 5-N Which is the “warmer” colour? and Event
5-O Hot Car show that black absorbs heat well and
white reflects most of the heat energy that hits it

All objects whose temperature is above absolute
zero radiate (give off) some heat
◦ The temperature must be very hot before we can feel it

Event 5-P Heat from Light shows the radiation
that a light bulb gives off
◦ The heat below the light bulb is from radiation
◦ The heat above the light bulb is from radiation and
convection

If you had a fire in a fireplace, where would you
feel the radiant heat? Where would you feel the
convection heat?

Almost all substances expand when heated
and contract when cooled
◦ Index of expansion - the amount of expansion or
contraction
◦ When heated, molecules vibrate more and take up
more space

Water is an exception
◦ It expands and contracts like other substances only
when it is above 4°C
◦ Below 4°C it expands when cooled
◦ This allows ice to form on top of water instead of at
the bottom

Interesting facts:
◦ Sears Tower in Chicago is about 15 centimeters
taller on a hot summer day than on a cold winter
day
◦ A 2km bridge can expand and contract about 1m
between summer and winter
◦ Concrete highways and sidewalks have separation
or joints to allow them to expand and contract
without breaking

Event 5-Q Dancing Dimes shows how air
expands when heated, rises up and pushes
past the coin
◦ When will the coin stop “dancing”?
 When the air inside the bottle reaches room
temperature
 Note: the coin must have an airtight seal – wet the rim
on the bottle with water

Event 5-R Jumping Juice (see safety note)
◦ Hot water on outside of beaker causes the coloured
water to rise in the tube. Why?
◦ Cold water on the outside of beaker causes the
coloured water to drop in the tube. Why?

Event 5-S The Sagging Solid shows that
different metals have different expansion
rates
◦ Metal strip is bimetal (iron side and brass side)
◦ The metal that expands more will be on the outside
of the curve
◦ Which metal expands more?
 Similar to 2 humans running a
track. The outer lane is longer, so
the runner has to run farther and
faster to keep up with the runner
in the inner lane

Event 5-T Expansion Meter shows how heat
causes metal to expand
◦ What happens to the weight as the wire is heated?
See Safety
Caution
Fig 5.12
page 85 in text

Event 5-U Expansion of Gases shows how
much air expands when heated
◦ Air expands as it heats, rises and travels along the
tube and into the inverted bottle
Fig 5.13 page 86 in text


Fire is a chemical source of energy
It releases energy by rearranging the atoms
of the object that is burning
◦ A candle is a hydrocarbon – made of hydrogen (H)
and carbon (C) atoms
◦ When it burns, oxygen (O) is bonded with the
hydrogen and carbon atoms
◦ Carbon dioxide (CO2) and water (H2O) are produced
◦ Event 5-V Water from Fire shows how fire
releases water
 Hydrogen atoms of candle combine with oxygen
atoms in air to produce water which condenses
on the cold glass
Fire Triangle – the 3 things fire needs in order to burn:
1. Fuel
2. Oxygen
3. Kindling temperature – the temperature that
something will ignite at (different for different
materials)


Fire will go out when 1 of these 3 things is
missing
Fire is a form of rapid oxidation because it
uses oxygen quickly

Event 5-W Boil Water in a Paper Cup shows
how flame is extinguished when the
kindling temperature is missing
◦ The water in the paper cup takes the heat away
from the paper quickly, so the paper never
reaches the kindling temperature
◦ The paper cup never burns, but the water boils
◦ Caution: Do not use plastic or Styrofoam cups.
Why?
 Plastic will melt
 Styrofoam is a good insulator so water cannot take
the heat away fast enough and the styrofoam will
burn, releasing fumes

Event 5-X Kindling Temperatures shows that
different substances have different kindling
temperatures
◦ Some substances will ignite quickly at low
temperatures
◦ Some substances will take more time and higher
temperature to ignite
◦ Caution: Do this in an area with lots of ventilation
due to fumes and odours


When oxygen combines with other materials, it
produces heat
Slow oxidation occurs when the heat is so little
that you cannot detect it
◦ When iron combines with oxygen to produce rust, it
produces heat that is not noticeable

Event 5-Y Heat from Grass is a demonstration of
slow oxidation
◦ Heat is produced in the moist grass as microorganisms
use the moisture to break down grass
 Moist grass breaks down in 1-2 days
 Dried hay (a type of grass) has no moisture, so can be
stored by farmers in a barn for years
Task:
 Groups of 2-4 discuss and explain the following
in writing:
“If hot air rises, then why is it so cold in the mountains?”


Tell students to use the words: conduction,
convection and radiation in their answer
Evaluation: