Transcript Slide 1

Welcome
M A Ps
Meaningful Applications of Physical Science
Dr. M. H. Suckley & Mr. P. A. Klozik
Email: [email protected]
Naïve Ideas
A. Nature of Heat
B. Expansion and Contraction
C. Heat Transfer
D. Change of State (Latent Heat)
E. Relating Heat, Energy and YOU
A. Nature of Heat
1. The Production of Heat and Other Forms of Energy
a. Where Does Heat Energy Come From? . . . . . . . . . . . . . . . . . .11
b. Transformation of Chemical Energy to Heat Energy . . . . . . . . .11
2. Different Materials Absorb Heat Energy at Different Rates
a. Colors and the Absorption of Heat Energy . . . . . . . . . . . . . . . 13
b. Different Materials and Their Absorption Of Heat Energy . . . . 15
3. Temperature and Heat
a. Sensing Temperature – The Three Tubs . . . . . . . . . . . . . . . . . 23
b. How Is Temperature Different From Heat? . . . . . . . . . . . . . . . 20
c. What Happens to Temperature When Water Changes State . . 24
B. Expansion and Contraction
1. The Addition of Heat Energy Usually Causes Solids To Expand
a. The Expanding Shower Curtain Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
b. Ball and the Ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
c. Bimetallic Strip and Linear Expansion and Contraction . . . . . . . . . . . . . . Demo
2. The Addition of Heat Energy Usually Causes Liquids to Expand
a. How Can You Compare the Expansion of Liquids . . . . . . . . . . . . . . . . . .35
b. Hand Boilers and Lava Lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
c. Liquids, Heat and Lake Turnover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slide
3. The Addition of Heat Energy Usually Causes Gases To Expand
a. Measuring the Expansion of Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
b. Crushing the Can (Ditto/Soda Cans). . . . . . . . . . . . . . . . . . . . . . . . . . . . . Demo
c. Nerf Ball Cannons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Demo
d. Egg in the Milk Bottle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Demo
e. Hero’s Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Demo
4. Measuring Temperature Using the Principle Of Expansion
a. Making and Calibrating A Thermometer. . . . . . . . . . . . . . . . . . . . . . . . 48
C. Heat Transfer
1. Heat Moves From Areas Of Higher Temperatures To Lower
a. Placing A Metal Strip in Hot Water . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
b. Match and Fork and Copper Coil in Flame. . . . . . . . . . . . . . . . . . . . . 55
2. Temperature Equilibrium
a. The Affect of Heated Objects On Their Surroundings . . . . . . . . . . . . . 57
b. The Law of Conservation of Heat Energy . . . . . . . . . . . . . . . . . . . . . . Slide
c. Mixing Water of Different Temperatures . . . . . . . . . . . . . . . . . . . . . . . 60
3. Conduction
a. How Quickly Does Heat Energy Travel?. . . . . . . . . . . . . . . . . . . . . . . . . 67
b. Conducting Heat Energy through Metals . . . . . . . . . . . . . . . . . . . . . . . 71
4. Convection
a. The Boiling Pot - Rheoscopic Fluid (Hot Plate & Beaker) . . . . . . . . . . . 76
b. Building a Heat Mobile . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 79
c. Why Does the Water Mix (Convection Currents). . . . . . . . . . . . . . . . . . 80
Why Does the Water Mix (Baby Food Jars) . . . . . . . . . . . . . . . . . . Demo
Aquarium (Cold Water) and Bottle (Hot Water) . . . . . . . . . . . . . . . . Demo
d. Movement of Air Through A Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5. Radiation - Using Cans to Transfer Heat Energy . . . . . . . . . . . . .87
6. Insulators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slide
D. Change of State (Latent Heat)
1. Change of State and Temperature . . . . . . . . . . . . . . . . . . . . . 95
2. Evaporation and Temperature (3 Sprays) . . . . . . . . . . . . . . . . 98
3. Drinking Bird . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Demo
4. Boiling, Bubbles, And Temperature . . . . . . . . . . . . . . . . . . . . .121
5. Heat Packs and Latent Heat . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6. Water Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .110
E. Relating Heat, Energy and YOU
. . . . . . . . . . . . . . .112
We Had A Great Time
Naive Ideas
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
14
Heat is a substance.
Temperature is a property of a particular material.
The temperature of an object depends on its size.
Heat and cold are different.
When heat is applied temperature always increases.
All solids expand at the same rate.
All liquids expand at the same rate.
All gases expand at the same rate.
Objects of different temperatures in contact with each other, do not
move towards the same temperature.
Heat energy only travels upward (rises).
Objects which warm quickly do not cool quickly.
The temperature of Ice always remains constant.
The bubbles in boiling water contain "air", "oxygen", or "nothing”.
All liquids boil at 100°C (212°F) and freeze at 0°C (32°F).
Where Does Heat Energy Come From?
1. HEAT ENERGY FROM MECHANICAL ENERGY:
Rubbing Hands
Bending Metal (coat hanger)
Hammering a Nail (hammer, nail, piece of wood)
Shaking (2 Styrofoam cups, sand, strong tape, thermometer)
2. HEAT ENERGY FROM CHEMICAL ENERGY:
Heat Pack
Cold Pack
Plaster of Paris
3. HEAT ENERGY FROM LIGHT ENERGY:
Light Bulb
Sun Light
1
2
Energy Conversions
Heat
Light
Mechanical
Fire
Expansion
Heat
Sound
Teapot
Electrical
Chemical
Thermocouple
Cooking
Food
0
5
Transformation Of Chemical Energy To Heat Energy
1. Light a Match
OR
2. Add water to Plaster of Paris, while constantly stirring, until syrupy.
OR
3. Heat energy stored in food:
a. obtain a piece of cardboard approx. 15-cm square
and cover with aluminum foil.
b. insert a straight pin through the cardboard and
aluminum foil.
c. place a peanut on the pin and light using a match.
2
Temperature
Temperature is a measure of the average kinetic energy associated with the
disordered microscopic motion of atoms and molecules. Temperature is not
directly proportional to internal energy since temperature measures only the
kinetic energy part of the internal energy, so two objects with the same
temperature do not in general have the same internal energy.
Temperatures are measured in one of the three standard temperature scales
(Celsius, Kelvin, and Fahrenheit).
4
Heat
Heat may be defined as a form of energy existing as the result of the
random motion of the molecules and is in transit from a high temperature
object to a lower temperature object. The amount of this energy is
dependent upon the temperature change, mass of the material and the
heat storing capacity, specific heat, of the material.
Heat = Mass x T(change in temperature) x c(Specific Heat)
H = M x T x c
3
4
Thermometers
Fahrenheit scale - Daniel Fahrenheit made a thermometer, stuck it in
freezing water and marked the level of the mercury on the glass as 32
degrees and then stuck the same thermometer in boiling water and
marked the level of the mercury as 212 degrees. The distance between
those two points were divided into 180 divisions.
Celsius scale - Anders Celsius arbitrarily decided that the freezing and
boiling points of water would be separated by 100 degrees. The boiling
point of water became 100 and the freezing point became 0 degrees.
Kelvin Scale - The International System of Measurements (SI) uses the
Kelvin scale for temperature. The Kelvin scale is based on the concept of
absolute zero, the theoretical temperature at which molecules would have
zero kinetic energy. Absolute zero, which is about -273.15 oC, is set at
zero on the Kelvin scale. This means that there is no temperature lower
than zero Kelvin, so there are no negative numbers on the Kelvin scale.
2
Comparison of Thermometers
.
Comparison of Temperature Scales
Set Points
Fahrenheit
Celsius
Kelvin
water boils
212
100
373
98.6
37
310
water freezes
32
0
273
absolute zero
-460
-273
0
body
temperature
1
Sensing Temperature – The Three Tubs
Get three bowls big enough to put your hands in. Fill one of them with very warm
(but not boiling) water, and fill the second with cold water. Then pour equal amount
s of hot and cold water into the third bowl.
Okay now, put one hand in the warm water and the other hand in the cold water
for, say, a minute. Now one at a time put your hands in the in-between bowl of
water.
Ice
Water
Room
Temperature
Hot
Water
The hand in hot water will sense cold and the hand in cold water will feel warmth. It’s hot and cold at the same time!
0
Thermal Properties of Selected Materials:
Specific Heat
Thermal
Expansion:
cm/cm oC
Thermal
conductivity:
cal/sec cm oC
Substance
Calories
cal/g oC
Aluminum
0.220
0.921
0.000026
0.4900
Brass
0.087
0.364
0.000019
0.2600
Copper
0.091
0.381
0.000017
0.9200
Glass
0.160
0.669
0.000009
0.0020
Iron
0.110
0.461
0.000011
0.2000
Joules
J/g K
Steel
0.000011
Lead
0.030
0.126
0.000029
0.0830
Water
1.000
4.187
0.001430
0.0014
Ice
0.500
2.094
0.001326
0.0040
Wood
0.420
1.759
0.000400
0.0002
Sand
0.200
0.837
1
Color Absorption
0
Materials and Their Absorption of Heat Energy
Observe materials and record perceived and actual temperatures
Material
Perceived Temperature (Place check)
Foam Rubber
__cold, __cool, __room temp., __warm, __hot
Sand
__cold, __cool, __room temp., __warm, __hot
Glass Marbles
__cold, __cool, __room temp., __warm, __hot
Steel Shot
__cold, __cool, __room temp., __warm, __hot
Gravel
__cold, __cool, __room temp., __warm, __hot
Wool Fabric
__cold, __cool, __room temp., __warm, __hot
Plastic Shot
__cold, __cool, __room temp., __warm, __hot
Lead Shot
__cold, __cool, __room temp., __warm, __hot
Lamb's Wool
__cold, __cool, __room temp., __warm, __hot
Potting Soil
__cold, __cool, __room temp., __warm, __hot
Actual Temperature °C
Water Cycle
Expansion of Solids
The Expanding Shower Curtain Rod
Figure 1
Wooden Dowel
Pin/wire
Curtain Rod
Block of Wood
Laser
PVC Pipe
Figure 2
Mirror
Figure 3
Ball and Ring
The ball easily
passes through
the ring at room
temperature.
After heating the
ball it no longer
pass through the
ring.
Expansion of Liquids
Hand Boilers and Lava Lamp
Hand Boilers
1
Lava Lamp
Conduction
Conduction is the transfer of energy through matter
from particle to particle. It is the transfer and
distribution of heat energy from atom to atom within a
substance. For example, a spoon in a cup of hot soup
becomes warmer because the heat from the soup is
conducted along the spoon.
Conduction is most effective in solids-but it can
happen in fluids. Fun fact: Have you ever noticed that
metals tend to feel cold? Believe it or not, they are
not colder! They only feel colder because they
conduct heat away from your hand. You perceive the
heat that is leaving your hand as cold.
1
Heat Conduction
Heat moves from higher
temperature to lower
temperature
T2
T1
0
Convection
Convection is the transfer of heat by the movement
of the warmed matter. Convection is the transfer of
heat energy in a gas or liquid by movement of
currents. The heat moves with the fluid.
Hot water rises, cools, Heated air rises, cools, then
falls. Air near heater is
and falls.
replaced by cooler air,
and the cycle repeats.
What if coils
were at the
bottom?
4
Convection Currents
This picture shows a gas burner and its
shadow on a screen. The flame gives
rise to a plume of hot gases that rise
above the burner. This disturbs the air
and casts a shadow, which reveals how
the moving air carries away the energy of
the flame: an example of energy transfer
by convection
3
Natural Convection
Air above warmer ground An Inversion layer is a laver
rises.
of air near the ground that
is more dense than air
higher up; no convection
currents to lift pollutants.
In a forest fire very
hot, low-density
air is buoyed upward,
carrying thermal
energy with it.
2
Sea Breezes
1
Urban Heat Islands
Cities are hotter than surrounding country because:
1. Re-radiation from concrete, asphalt, etc.
2. Industrial & human activity.
3. Quick overland flow eliminates evaporative cooling.
0
Heat Mobile
1
Why Does the Water Mix?
1. Fill one jar to the top with hot water.
(It must be filled to the very top).
2. Fill the other Jar with cold water and add
several drops of food coloring to it.
3. Put the index card on top of the hot water
jar, hold the card in place, and turn the jar
upside down, placing it on top of the cold
water jar.
4. Slide the card out slowly and watch what
happens.
8
Radiation
HEAT RADIATION is electromagnetic waves that directly
transport energy through space. Sunlight is a form of
radiation that is radiated through space to our planet at the
speed of light without the aid of fluids or solids. The energy
travels through nothingness! Thus, radiation brings heat to
our planet.
Energy is used to broil a fish. The red glow on the
heating element is the visible part of the light energy,
but there is far more invisible infrared light being emitted.
Energy is transferred as electromagnetic energy from
the heating element to the fish: an example of transfer of
energy by radiation.
3
Heat Radiation Due to Color
Fill each can with equal amounts
of hot water. Place a lid with a
thermometer inserted on each
can.
MEASURE the initial temperature
in each can. RECORD the
temperatures in the table.
2
Heat Radiation Due to Color
14
Time
Black Can
White Can
Silver Can
0
93.0
93.0
93.0
5
80.5
83.0
84.0
10
74.0
77.0
80.0
15
70.0
73.0
76.8
20
66.0
69.2
73.5
25
62.5
65.5
71.0
30
59.5
62.5
68.0
35
57.0
59.5
66.0
40
54.5
57.0
63.8
45
53.0
55.2
62.0
50
51.0
54.0
61.2
55
49.0
51.5
58.5
60
47.2
49.5
57.0
65
46.0
48.0
55.2
1
Graph - Heat Radiation Due to Color
95.0
85.0
Silver
75.0
White
65.0
Black
55.0
45.0
35.0
0
5 10 15 20 25 30 35 40 45 50 55 60 65
0
Insulators
Ice upon freezing gives up heat to
plants. Ice also has a low thermal
conductivity.
Ice on cooling coils will
slow the removal of thermal
energy from the air.
Bimetallic Strip
The principle behind a bimetallic strip thermometer relies on
the fact that different metals expand at different rates as they
warm up. By bonding two different metals together, you can
make a simple electric controller that can withstand fairly high
temperatures. This sort of controller is often found in ovens.
1
How Can You Explain The Sagging
Telephone Line?
Winter
Summer
0
1
Thermometers
Fahrenheit scale - Daniel Fahrenheit made a thermometer, stuck it in
freezing water and marked the level of the mercury on the glass as 32
degrees and then stuck the same thermometer in boiling water and
marked the level of the mercury as 212 degrees. The distance between
those two points were divided into 180 divisions.
Celsius scale - Anders Celsius arbitrarily decided that the freezing and
boiling points of water would be separated by 100 degrees. The boiling
point of water became 100 and the freezing point became 0 degrees.
Kelvin Scale - The International System of Measurements (SI) uses the
Kelvin scale for temperature. The Kelvin scale is based on the concept of
absolute zero, the theoretical temperature at which molecules would have
zero kinetic energy. Absolute zero, which is about -273.15 oC, is set at
zero on the Kelvin scale. This means that there is no temperature lower
than zero Kelvin, so there are no negative numbers on the Kelvin scale.
1
Comparison of Thermometers
.
Comparison of Temperature Scales
Set Points
Fahrenheit
Celsius
Kelvin
water boils
212
100
373
98.6
37
310
water freezes
32
0
273
absolute zero
-460
-273
0
body
temperature
0
How Is Temperature Different From Heat?
1. Place the two bolts into a beaker of water. Heat the water until it bolls
for several minutes. Are the bolts at the same temperature?
2. What is the temperature of the bolts?
3. Use the tongs to remove the large bolt from the hot water.
4. Read temperature of hot water and immediately put it in one of the
cups of tap water.
5. MEASURE and RECORD any changes in the water temperature for
a period of three minutes.
Initial
Temperature
1 Min.
2 Min
3 Min.
Lake Turnover
Spring: Surface ice (0°C) melts and becomes denser when it warms to 4°C, and then
sinks. This sinking, along with spring winds, causes mixing of water until all
the water becomes 4°C. This is Spring Turnover, which results in mixing the
O2 rich upper waters with nutrient-rich lower waters.
Autumn: Time of fall turnover. The surface cools and becomes denser and sinks. Again,
nutrient- and oxygen-rich waters will mix, and the "fall bloom" will occur.
Measuring The
Expansion Of Air
What Happens When Water Changes State
Time - min
L atent Heat
0
Temp.
5
Gas
Boiling
100
10
540 cal/gr.
15
Liquid
1 cal/gr. for
each degr ee
20
melt ing
0
25
80 cal/ gr
solid
30
-30
0
5
Time
Temp. - 0C
10
15
20
25
30
35
40
Calories per gram needed for change in State
45
35
40
45
1
What Happens When Water Changes State
L atent Heat
Temp.
Gas
Boiling
100
540 cal/gr.
Liquid
1 cal/gr. for
each degr ee
melt ing
0
80 cal/ gr
solid
-30
0
5
Time
10
15
20
25
30
35
40
45
Calories per gram needed for change in State
0
Change of State and Temperature
Latent Heat
Boiling
540 cal/gram
Latent Heat
Temp.
Gas
Boiling
100
Heating
1 cal/gram per
degree
Liquid
melting
0
Melting
80 cal/gram
solid
-30
0
5
Time
10
15
20
25
30
35
40
Calories per gram needed for change in State
45
Drinking Bird
When water evaporates from the fuzz on the Dippy Bird's
head, the head is cooled. The temperature decrease in
the head condenses the methylene chloride vapor,
decreasing the vapor pressure in the head relative to the
vapor pressure in the abdomen.
The greater vapor pressure in the abdomen forces fluid up
through the neck and into the head. As fluid enters the
head, it makes the Dippy Bird top-heavy.
The bird tips. Liquid travels to the head. The bottom of the
tube is no longer submerged in liquid.
Vapor bubbles travel through the tube and into the head.
Liquid drains from the head, displaced by the bubbles.
Fluid drains back into the abdomen, making the bird
bottom-heavy.
The bird tips back up
The Heat Pack and Latent Heat
The heat pack contains a solution of sodium acetate tri-hydrate in
water. This solution has a very large heat of crystallization, which
means it gives out a significant amount of energy on solidifying or
crystallizing. (temperature rise to around 50 °C). This ability to
store heat energy in is referred to as latent heat.
1
Data: Conservation of Energy
Mcold-water Cup (g)
Trial 2
200-g. hot + 100-g. cold
Trial 3
75-g. hot +225-g. cold
3-g
3-g
3-g
MH20,cold-water + Cup (g)
150-g
100-g
MH20,cold (g)
147-g
97-g
225-g
3-g
3-g
3-g
150-g
200-g
79-g
Mhot-water Cup (g)
MH20,hot-water + Cup (g)
228-g
MH20,hot (g)
147-g
197-g
76-g
Thot
81-°C
75-°C
82-°C
3-°C
1-°C
4-°C
TFinal (oC)
40-°C
51-°C
24-°C
Thot (oC)
41-°C
24-°C
59-°C
(oC)
Tcold (oC)
Tcold (oC)
37-°C
50-°C
20-°C
Heat gain: (c)
Hcold = MH20,cold x Tcold x c
5439
4850
4520
Heat loss: (c)
Hhot = MH20,hot x Thot x c
6027
4728
4484
Theoretical Value
5733
4789
Percent of Error
5.13
1.27
Does Heat Loss Equal Heat Gain?
27
Trial 1
150-g. hot + 150-g. cold
4502
0.4
How Quickly Does Heat Energy Travel?
1. Take each metal and hold it for about 10 seconds. DESCRIBE how
each material feels to your hand.
2. Carefully pour hot water into the Styrofoam cup. Place all the strips in
the cup at the same time. Touch the ends of the strips to see which
one gets warm first. List the ORDER in which the materials get warm.
3. CLASSIFY each of these materials as good heat conductors, fair heat
conductors, or poor heat conductors.
Copper
Aluminum
Iron
Plastic
Wood
Conducting Heat Energy through Metals
Lay the copper strip on the
table. Make pencil lines at 2cm intervals along the strip.
Use a match to slightly melt
the bottoms of the birthday
candles and stick them on.
Turn the strip over and place
it upside down over the ring.
Light the burner and place it
under one end of the strip.
Light the candle and allow a small
drop of wax to drip onto the end of
each metal rod. While the wax is
still liquid, attach a small strip of
paper to each rod.
Light the burner and place it
under the center of the apparatus.
MEASURE and RECORD the
time that it takes for the paper
strips to fall off the rod.
Placing A Metal Strip in Hot Water
Place the end of the
straight strip of metal in
the cup of hot water.
Wait about 15 seconds
and then DESCRIBE
what you feel when you
touch the top of the
strip.
Bend strip and repeat.
Match and Fork and Copper Coil in Flame
Kindling Point
Heated Objects Affect On Their Surroundings
Insert a thermometer in each rubber stopper.
Mount the stoppers in the holes in the cardboard.
Fill the test tube with hot water.
Place one stopper and thermometer in the test tube.
Place the whole lid assembly over a Styrofoam cup.
MEASURE the initial temperatures of both the air
and the water.
Continue measuring and recording the temperatures
at one minutes intervals for six minutes.
Thermometer
Placement
Hot Water
Air
Temperature (Each Minute)
0
1
2
3
4
Cup Size
5
6
Small
Medium
Large
The Law of Conservation of Energy
2
Heat Lost
=
m x ∆T x c
=
Heat Gained
m x ∆T x c
Heat, Energy,
And YOU!
Trial
1
2
3
Av.
Force
F (newtons)
Distance
d(meters)
Work
W (joule)
Calories
cal. = W / 4.19
We Had A Great Time