Transcript Ch 6 Electricity for everyone - San Juan Unified School District

CH 6 ELECTRICITY FOR EVERYONE
GREEN ENERGY AND HOME DESIGN
FIND OUT
1. What is “green energy”?
2. What is a “carbon
footprint”?
3. Why should you care?
4. How can you reduce
your carbon footprint?
Record answers and
examples in your
notebook
p152
INVESTIGATION #1 (P598)




What do you see in the
cartoon?
Turn and tell your
partner 2 things
Share out
Record in your notebook
p153
WHAT DO YOU THINK? (P598)





p153
Record in your notebook
Usually, when you need
electricity, all you have to do
is plug an appliance into the
wall
How is the electricity that you
use generated?
Make a list of energy sources
Compare with a partner
PART A
p153
1a.) Where does electricity come from? Circle the
sources on the handout.
1b.) How does it get to your house?



All Sacramento county households get their electricity
from SMUD (Sacramento Metropolitan Utility District)
and natural gas from PG&E (Pacific Gas and
Electricity)
https://www.smud.org/en/about-smud/companyinformation/power-sources.htm
Ask for a copy of your most recent SMUD bill. Make a
LIST WHAT APPLIANCES ARE NEEDED IN
YOUR HOUSE:
p153
Basic (world)
Compare with a partner
Basic (USA)
Dream house
PART A: APPLIANCES BY ENERGY USE
p153
**Highest energy user:
Air conditioning/heater
Clothes dryer
freezer
Hot water heater
Refrigerator
*Medium energy users:
TV/computers
Dishwasher
Toaster/oven
Cell phone
Microwave
Hair dryer
video games
Low energy users:
Fans
Stereo/boom box
Lights
coffee maker
PART A: HOW MANY PHYSICS STUDENTS
DOES IT TAKE TO LIGHT A LIGHT BULB?
Using only the items in the
bag, make the light bulb
glow.
 Draw a picture in your
notebook
 Explain what you think is
happening

p154
PART B (P599-600) STEPS 1-3 ONLY P154
Equipment in the box on the lab bench
 Hand generators can break (and cost $$)
 Crank them slowly and gently
 Get your notebook stamped when you are
finished and put everything back in the box.
 Answer CU (p601) 1-3
P155
PtoGo (p604) 1-9
Get your notebook stamped again

INVESTIGATION #2 (P606-609)
THE ELECTRON SHUFFLE

P156
What do you see in the picture? Turn and share
2 things that you see with your neighbor
What do you think? What is electricity and how
does it move through a circuit? Record your
ideas in your notebook…
 Share out

INVESTIGATION 2: THE ELECTRON SHUFFLE
PART A: MODELING A SIMPLE CIRCUIT
Volunteer to be the battery:
 Volunteer to be the light bulb (how do we know
when the bulb is “on”?)
 Everyone else is an electric charge (electron)in
the circuit
 Arrange yourselves into a complete circuit
 Round 1

ROUND 1 (RECORD IN YOUR NOTEBOOK)



The battery (source of beads)
gave each unit of charge
(student electron) a certain
amount of energy (one
bead).The charge then gave
that energy to the light bulb
(dancing student) who
converted the energy into light,
The charges (student electrons)
continue back to the battery to
get more energy and repeat the
process.
1 volt battery means…
1 amp means…
ROUND 2: ADD VOCALS




p156
The battery announces “the
battery voltage is 1 volt which
equals one joule of energy for
each coulomb of charge”
Any student receiving a bead
responds “one coulomb of
charge receiving one joule of
energy”
Teacher says “please move
along, one coulomb per second
is one ampere (amp) of
current”
The light bulb says “I just
received one joule of energy
from that coulomb of charge”
This is the ELECTRON SHUFFLE. What are the
variables that we could change?
p156
Round 3
 Voltage=3 volts means…
(battery gives each charge 3
joules of energy)
 Current=1 amp means…
( coulomb of charge moves
by every second)


Record what happens

Round 4
Voltage=1volt means…

Current=2 amps means…

Record what happens

ELECTRICITY MODEL: SECTION 1
DQ: HOW DOES ELECTRICITY WORK?
p157
1. Electricity is created when electrons move from one
place to another. Electricity can also be created when
work is done to move a magnet within a coil of wire
(generator)
2. Electrons move to places with less negative charge
(opposite charges attract, similar charges repel)
3. Energy can be transferred from one type to another.
4. Power companies (like SMUD) get electricity from
different sources (hydro, gas, solar, wind, geothermal)
5. For an electric current to exist in a circuit, the circuit
must form a closed loop. Switches are used to open/close
a circuit. Metals conduct easily. Other materials do not
and act as insulators.
6. A fuse burns out if the current becomes too large
7. As the energy output of a circuit increases, the energy
ON YOUR OWN P608 #9
RECORD how the electron shuffle would
change under the following conditions:
p156
a.) there is a 5 volt battery
b.) current is 3 amps
c.) there is a two volt battery
d.) the current is increased to 5 amps
e.) the two-volt battery is replaced with a four-volt
battery
f.) the current increases from 2 amps to 3 amps
PART B: MODELING A SERIES CIRCUIT
p158
Now we need 2 light bulbs.
1a.) Describe what will happen if we put 2 bulbs in
our circuit, one right after the other.
 In order to have any light in the second bulb, an
electron (student) must keep some of the energy
from the first bulb (so less energy goes to the first
bulb) to give to the second. This is called
resistance. How much energy goes to the first bulb
depends on the bulb. For now, half of the energy
will go to the first bulb, and half to the second
bulb.

PART B (P608)
P158
2a.) Since the brightness of a bulb depends on
how much energy is used up in the bulb during
a given time, how would the brightness of each
of the 2 bulbs in the series circuit compare with
the brightness of a single bulb hooked up to
the same battery?
 3 A) 4 light bulbs in series result in…
 B) two light bulbs and a 3-volt battery
 C) two light bulbs, but twice as much current
 D) two different kinds of light bulbs in series

DRAW AND COMPLETE THE CHART FOR #4
(P609) 1 Bulb
2 Bulbs
Which is
voltage
current
voltage
current
brighter?
1
1
1
1
One bulb
1
1
2
1
1
1
1
2
1
1
2
2
2
2
4
1
2
2
2
3
4
1
3
2
Get a stamp
CU (p610) 1-4 Get a stamp
 PtoGo (p612-613) 1-4 Get a stamp

P159
DRAW AND COMPLETE THE CHART FOR #3
(P613) 1 Bulb
2 Bulbs
Which is
brighter?
voltage
current
voltage
current
1
1
3
1
same
1
1
3
1
Same
1
1
1
3
Same
1
1
6
2
3
4
2
9
1
1
2
3
3
3
1
4
1
3
2
1
P159
P160
INVESTIGATION 3
SERIES AND PARALLEL CIRCUITS (P614-617)

What do you see in the picture? Turn and share
2 things that you see with your neighbor
P160
INVESTIGATION 3
SERIES AND PARALLEL CIRCUITS (P614-617)

What do you see in the picture? Turn and share
2 things that you see with your neighbor
What do you think? When one light bulb in your
house goes out, can the other light bulbs
remain on? Can a circuit be set up to allow
this? Record your ideas in your notebook…
 Share out

INVESTIGATION #3
p160
PART A; MODELING A PARALLEL CIRCUIT
(RECORD IN YOUR NOTEBOOK)
 Back to our electron shuffle model…
 Round 1: Set up a series circuit. What happens
again when we put a second bulb into this
series circuit? Draw a picture of this circuit.
 Round 2: Now we are going to make a parallel
circuit. At a certain point, a junction, electrons
will have to choose which light bulb to give their
energy to. Draw a picture of this circuit.
ROUND 2 (2 BULBS IN PARALLEL): JAN-JUN GO TO BULB ONE
JUL-DEC BULB TWO
p160




The battery announces “the
battery voltage is 1 volt which
equals one joule of energy for
each coulomb of charge”
Any student receiving a bead
responds “one coulomb of
charge receiving one joule of
energy”
Teacher says “please move
along, one coulomb per
second is one ampere (amp) of
current”
The light bulb says “I just
received one joule of energy
from that coulomb of charge”
Record in your notebook:
 1 volt battery means…
(battery gives each charge 1 joules
of energy)
1 amp means…
(1 coulombs of charge move by
every second)

3.)Record what happens:
The battery:
The electrons:
The light bulbs:
p160
4A.) THE BATTERY PROVIDED EACH COULOMB
OF CHARGE WITH ONE JOULE OF ENERGY. HOW
MUCH ENERGY DID EACH LIGHT BULB GET FROM
EACH COULOMB OF CHARGE?
Each light bulb receives one joule (bead) for each
coulomb of charge (from each student electron)
that passes through the light bulb.
4B.) THE CHARGES LEFT THE BATTERY AT THE
RATE OF ONE COULOMB PER SECOND. WHAT
WAS THE CURRENT THROUGH EACH LIGHT
BULB?
(1volt)(1amp)/2 bulbs=
 Because the current divides equally among the
light bulbs, each light bulb receives an equal
share of the coulomb of charge . 2 bulbs
means each bulb gets one half.
ROUND 3 (3 BULBS IN PARALLEL): JAN-APR BULB ONE, MAYAUG BULB TWO, SEP-DEC BULB THREE




The battery announces “the
battery voltage is 1 volt which
equals one joule of energy for
each coulomb of charge”
Any student receiving a block
responds “one coulomb of
charge receiving one joule of
energy”
Teacher says “please move
along, one coulomb per
second is one ampere (amp) of
current”
The light bulb says “I just
received one joule of energy
from that coulomb of charge”
Record in your notebook:
Draw a picture of this circuit
p160
4C.) THE BATTERY PROVIDED EACH COULOMB
OF CHARGE WITH ONE JOULE OF ENERGY. HOW
MUCH ENERGY DID EACH LIGHT BULB GET FROM
EACH COULOMB OF CHARGE?
Each light bulb receives one joule (bead) for
each coulomb of charge (from each student
electron) that passes through the light bulb.
(same amount as the last round= 1 charge from
each student)

4D.) THE CHARGES LEFT THE BATTERY AT THE
RATE OF ONE COULOMB PER SECOND. WHAT
WAS THE CURRENT THROUGH EACH LIGHT
BULB?
(1VOLT)(1AMP)/3 BULBS=

Three bulbs means each bulb gets 1/3 per
second (different amount of current than the
last round)
CONTINUE RECORDING:
p160
Round 4
 Voltage=3 volts (battery
gives each charge 3
joules of energy)
 Current=1 amp (1
coulombs of charge
move by every second)
Round 5
 Voltage=1 volt (means…)

Current=2 amps
(means…)
HOW DOES A PARALLEL CIRCUIT CHANGE
UNDER THESE CONDITIONS? (1 VOLT AND 1 AMP)
7a.) 4 bulbs in a parallel circuit (the current
passing by each light bulb would be…)
(1 volt)(1 amp)/4 bulbs=
One fourth (1/4) coulomb per second or one
student passing by every 4 seconds
p160
HOW DOES A PARALLEL CIRCUIT CHANGE
UNDER THESE CONDITIONS? (3 VOLT AND 1 AMP)
p159
7b.) three light bulbs and a 3 volt battery
(3volts)(1amps)/3bulbs=
Three times the charge means three times as
bright
Each light bulb receives 1/3 of a coulomb of
charge per second=1 ampere
(Same brightness as 1 bulb with 1 volt and 1 amp)
HOW DOES A PARALLEL CIRCUIT CHANGE
UNDER THESE CONDITIONS? (1 VOLT AND 2 AMP)
p159
7c.) 3 light bulbs and larger current (2 amps)
(1 volt)(2 amps)/3 bulbs=
Each light bulb would still get the same amount
of energy per charge (student) passing by, and
1/3 the larger current, but there is twice as
much current, so each bulb would get 2/3
amps each
HOW DOES A PARALLEL CIRCUIT CHANGE p159
UNDER THESE CONDITIONS? (6 VOLT AND 1 AMP)
7d.) 4 light bulbs and 6 volts
(6 volts)(1 amp)/4 bulbs =
Each light bulb would receive six joules of energy
for every coulomb (student) that passes and
each light bulb would receive ¼ the current of
1 amp (one student would pass by every 1.5
seconds)
HOW DOES A PARALLEL CIRCUIT CHANGE
UNDER THESE CONDITIONS? (1 VOLT AND 1 AMP)
p159
7e.) 3 bulbs that are not identical
Each would get the same amount of energy per
charge (student), but different amounts of
charge because they are not identical (the
number of students passing by per second
would vary)
So each bulb would be a different brightness
ELECTRICITY MODEL: SECTION 2
p156
8. Electrical power is the speed that energy is transferred. Power
is measured in Watts (W)
9. Electric potential or voltage is the potential energy per unit of
charge, and is measured in volts 1 volt=1 joule/charge
10. Current is the amount of charge per unit of time that flows
past a point and is measured in amperes (amps) 1amp=1
charge/second
11. Resistors are electronic devices (like light bulbs) that resist
the flow of electric charge
12. In a series circuit there is one path for current to follow. The
sum of the voltage dropped at each resistor is equal to the total
voltage supplied to the circuit (2 light bulbs in series: each gets ½
the voltage and are therefore ½ the brightness)
PHET: Some Properties of Electric Circuits
PART VI
Resistance
Current0.60
Voltage
10
0.90
9.00
15
0.60
9.00
20
0.45
9.00
25
0.36
9.00
30
35
40
a) What is the relationship
between resistance and
current?
b) What is the relationship
between resistance and
voltage?
c) Explain
45
50
55
THIS IS OHM’S LAW:
V=IR
PART B: COMPARING SERIES AND PARALLEL
CIRCUITS
P160
Use Phet: Circuit Construction Kit (DC only)
 Follow directions and answer questions on the
handout (Some properties of electric circuits)
 Get a stamp when finished
 CU (p618) 1-4
P161 PtoGo (p621-622) 1-4
162
 CU (p626) 1-3
 Get stamps when finished

ELECTRICITY MODEL: SECTION 3
p156
13. In a series circuit current flows along one
path. In a parallel circuit the current flows along
parallel paths.
14. The voltage drop
across each branch
is equal the total
voltage
15. The sum of the
current in each branch
equals the total current
SECTION 4 (P623)

p151
What do you see in the picture? Turn and share
2 things that you see with your neighbor
SECTION 4 (P623)

p151
What do you see in the picture? Turn and share
2 things that you see with your neighbor
What do you think? What determines the
brightness of a bulb? What determines how
much current flows in a circuit? Record your
ideas in your notebook…
 Share out

INVESTIGATION
p152
Today you will use the phet simulation: Circuit
Construction Kit (in place of the lab in the text
book)
 All parts should be completed today (before our
next class meeting)
 CU (p626) 1-3
 PtoGo (p629-630) 1-4
 CDP 33-2 34-1

p162
CU (p626) 1-3
 PtoGo (p629-630) 1-4


Quiz tomorrow!
ELECTRICITY MODEL: SECTION 4
p156
16. Voltmeters are used to measure voltage
(which is measured in volts or V)
17. Ammeters are used to measure current
(which is measured in amps or I)
18. Resistance is directly proportional to the
voltage dropped and inversely proportional to the
current
19. Resistance is measured in ohms
or Ω
20. Ohm’s Law: voltage=(current)(resistance)
PtoGo (p629)
p162
6. Your hair dryer has a resistance of 9.6 ohms and you plug it into the
bathroom outlet. Assume household voltage to be 120 volts, and that
different parts of your house are connected in parallel.
a.) What current will it draw?
I=V/R=120V/9.6=12.5 amps
b.)Suppose that your brother has an identical hair dryer and plugs it into
a parallel part of the circuit. What current will the two hair dryers
draw?
Parallel circuits have the same voltage drop and the same current…12.5
amps + 12.5 amps=25 amps total
c.) If the maximum current the circuit breaker in the system can handle
is 20 amps, what do you think will happen?
The circuit breaker will “break” when the current exceeds 20 amps
PtoGo (p629)
8.) A 12 volt battery is hooked up to a 3 ohm
resistor. The current through the resistor is
I=V/R=12/3=4 amps
p162
PtoGo (p630)
9.) A 2 ohm resistor has 4 amps of current
running through it. The voltage drop (or
potential drop) across the resistor is
V=IR=(4)(2)=8 volts
p162
SECTION 5 ELECTRIC POWER: LOAD LIMIT
(P631-643)

What do you SEE in the cartoon?
p154
SECTION 5 ELECTRIC POWER: LOAD LIMIT
(P631-643)

What do you SEE in the cartoon?
p154
SECTION 5 ELECTRIC POWER: LOAD LIMIT
(P631-643)
p154
What do you SEE in the cartoon?
 Use what you see, and your prior experience to
answer the questions What Do You Think in
your notebook
 What do you think is the function of a fuse or
circuit breaker?
 Exactly what conditions do you think make a
fuse blow or a circuit breaker trip?

INVESTIGATION
p154
1.) Watch the following demonstrations on
youtube
 Balloon fuse
http://www.youtube.com/watch?v=m3U4k_xTS
pU
 Electricity review
http://www.youtube.com/watch?v=l0nCSzqefn
w&feature=related
1a.) what happens to the light in the video when
the fuse blows?
TEACHER DEMO: When you plug a hot plate, a lamp with a 100
watt bulb, and a heater into a power strip and turn them all on at
the same time, the power strip will turn itself off.
p154
2a.) Why do you think that the fuse blew?
b.) Why did the circuit require multiple appliances
to blow out the fuse?
c.) Explain why the fuse behaves the way it does.
BELOW ARE THE APPLIANCE RATINGS:
Appliance
Voltage
Power (Watts)
Hot plate
120
800
Lamp with 100 Watt
bulb
120
100
heater
120
300
4.) Copy the table into your notebook.
5.) Calculate the current for each appliance I=P/V
6.) Find the total current and total power used above.
The current rating on the power strip was 10 A.
Did the total current of the appliances exceed that rating?
CU (p638) 1-4
PtoGo (p641-642) 1-13
CDP 34-2 35-1
Current (Amps)
p155
ELECTRICITY MODEL: SECTION 5
p157
20. Power is the rate at which energy is delivered to an object or a load in a
circuit. Power is measured in watts. One Watt is one joule of energy supplied in
one second of time (1 W= 1 J/s). For a circuit, the power can be calculated by
multiplying current and voltage (P=IV)
21. When the flow of electric charge, or current, occurs easily in a material it is
called a good electric conductor. When the material does not allow charge to
flow easily (or not at all) it is called an insulator.
22. Fuses and circuit breakers are used as safeguards to protect the circuit
from too much current and prevent electrical fires from starting. A fuse consists
of a wire that will melt when too much current flows through it, thus opening
the circuit. A fuse must be replaced when blown (to make a closed circuit). A
circuit breaker is a switch that opens when too much current flows through it. A
circuit breaker must be reset when tripped for current to resume flowing.
23. The power (and current) drawn by a circuit depends upon the voltage of the
circuit and the resistance of the circuit. Decreasing the resistance of a circuit
increases the power (and current) for a fixed voltage.
SECTION 6 CVR IN PARALLEL AND SERIES:
WHO’S IN CONTROL? (P644-659)

p158
What do you see? Many electrical switches are operated manually (by
hand), and many others are automatic, turning appliances on and off in response to a
variety of conditions.
SECTION 6 CVR IN PARALLEL AND SERIES:
WHO’S IN CONTROL? (P644-659)


p158
List at least 3 different kinds of automatic switching devices in the picture.
What are the conditions that cause the on/off action of the switch?
INVESTIGATE
p158
Today you will use the phet simulation: Circuit
Construction Kit (in place of the lab in the text
book)
 All parts should be completed today (before our
next class meeting)
 CU (p654) 1-3
 PtoGo (p658-659) 1-13
 CDP 35-2 35-3

ELECTRICITY MODEL: SECTION 6
p157
24. Switches are used to control the total circuit or part of a circuit.
25. Energy and charge are conserved in a circuit. Using these principles and Ohm’s Law
results in the following relationships for series and parallel circuits:
Series:
Parallel:
Vtotal = V1 + V2 + V3 etc.
Vtotal = V1 = V2 = V3 etc.
Itotal = I1 =I2 =I3 etc.
Itotal = I1 + I2 + I3 etc.
R total = R1 + R2 + R3 etc.
1/Rtotal = 1/R1 + 1/R2 + 1/R3 etc.
26. For any junction in a circuit, the current flowing into the junction must equal the
current leaving the junction.
27. The energy consumed in the parts of a circuit is equal to the the energy supplied by
the power source
28. Adding resistance in parallel decreases the circuit resistance and increases the
circuit current and power.
HOW CAN ELECTRICITY CREATE A MAGNET?
What is an electromagnet? How does it work?
 Draw and label the parts of an electromagnet

What is a simple test to tell if an electromagnet
is working?
 Video 1: http://www.youtube.com/watch?v=emlzh9XXWgQ
p164
 Video 2: http://www.youtube.com/watch?v=frYorKTKdeI
 Video 3: http://www.youtube.com/watch?v=_ygmHnjNYNo

ELECTROMAGNETISM
WATCH VIDEOCLIP FROM BRAVE LITTLE TOASTER
1.) What can the magnet
pick up?
2.) How do you think the
magnet is able to drop
things where they need
to go?
p164
NOW LET’S MAKE AN ELECTROMAGNET
1.) What is an
electromagnet made
from?
2.) How do you turn an
electromagnet off/on?
3.) What variables could
we change to make a
stronger electromagnet?
p164
BUILD AND TEST AN ELECTROMAGNET
PHET: MAGNETS AND ELECTROMAGNETS
HTTP://PHET.COLORADO.EDU/NEW/SIMULATIONS/SIMS.PHP?SIM=MAGNETS_AND_ELECTROMAGNETS
Follow the directions
and complete the
handout.
Get a stamp when
you finish each page.
Day 1: Finish part 1
Day 2: Parts 2-5
P164165
MAGNETIC NORTH
P166
The north pole is not the same place as the
magnetic north pole. Do the poles move?
 If the poles do move, how does that affect the
earth?


Youtube NOVA: Magnetic Storm
MAGNETISM MODEL
p165
1. The direction of a magnetic field outside a magnet is from north
to south (that is why a compass points north)
2. The earth’s magnetic field is caused by currents in the earth’s
core and changes over time.
3. All magnetic fields are produced by moving electric charges
(electromagnets use electricity). The field is perpendicular to the
wire. Changing the magnetic field changes both the current and
the voltage.
4. A moving charge is deflected when it crosses magnetic field
lines. This force can be used to do work. The magnetic field is
strongest near the center
5. A generator converts energy into electricity. A motor turns
electricity into mechanical energy.
6. Faradays law: electric fields are created when a magnetic field
changes
FLOWER
POWER
p167
PTO GO (P641) #1 ONLY SOLVE EACH PART (SHOW THE WORK)
Power
Voltage
10 V
Current
Resistance
1A
2Ω
3A
4Ω
4A
120 V
2400 W
1800 W
10 Ω
120 V
10 A
p167
HOW ELECTRICAL GRIDS WORK WEBQUEST
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

Summary
19-31
32-49
50-70
P168169
Get a stamp at the end of class
IT’S ALWAYS ABOUT ENERGY!
p170
When I hit the table with the hammer, where
does the energy come from? Where does it
go?
 When I hit 2 metal spheres together, where
does the energy come from? Where does it
go?

WHAT WILL HAPPEN WHEN YOU ADD 1 DROP OF
FOOD COLORING TO EACH BEAKER?
RECORD YOUR PREDICTION
AND THEN GENTLY ADD ONE DROP TO EACH
BEAKER.
Hot water
Observations:

Explanation:


P170
Cold water
Observations:
DISCUSS/ SHARE OUT AND RECORD




What is temperature a
measure of?
How does a
thermometer work?
What temperature
scales do you know?
What is absolute zero?
p171
DRAW A PICTURE OF 10 WATER MOLECULES
IN A CUP OF COLD WATER, AND THEN THE
SAME 10 MOLECULES OF WATER IN A WARM
CUP OF WATER (SAME SIZE CUP!)
p172

Explain how the two cups of water are
different
TEMPERATURE MODEL
DRIVING QUESTION: WHAT DOES TEMPERATURE
REALLY MEASURE?
p173
1. Measures the movement (speed) of
molecules (more energy=more speed)
2. As the molecule speed increases, the
molecules spread out taking up more space.
This is what happens in a thermometer.
3. Centigrade (Celsius), kelvin, Fahrenheit
4. Absolute zero is when molecules stop
moving and therefore take up zero space
(impossible!)
SECTION 7: LAWS OF THERMODYNAMICS
(P664-677)
p175
What do you SEE in the cartoon?
 Use what you see, and your prior experience to
answer the questions What Do You Think in
your notebook
 As you add cold milk to hot coffee, you expect
that the milk will get warmer, and the coffee will
get a bit colder. What determines the final
temperature of the coffee and the milk?

SECTION 7: LAWS OF THERMODYNAMICS
(P664-677)

What do you SEE in the cartoon?
p175
MIXOLOGIST
What happens if you mix 50ml of water
at 50oC and 50ml of water at 100oC?
 Explain:
 Try it! Investigation #7


Team 1 equal amounts of hot/cold
Team 2 2/3 hot:1/3 cold
Team 3 1/3 hot:2/3 cold
Team 4 equal amounts hot metal: cold water
Team 5 equal amounts cold metal: hot water
Team 6 equal amounts hot metal: cold water
Team 7 equal amounts cold metal: hot water

Was your prediction correct?






P175
INVESTIGATION #7

Team 1 equal amounts of hot/cold
Hot 53.5C: cold 3.4C

Team 2 2/3 hot:1/3 cold
Hot 45.5C: cold 4.0C

final 29C
final 29C
Team 3 1/3 hot:2/3 cold
Hot 48.3C: cold 4.5C
final 19.9C
Team 4 equal amounts hot nails: cold water
Hot 37.7C: cold 21.1C

final 22.8C
Team 5 equal amounts cold nails: hot water
Hot 48.2C: cold 3.7
final 43.5C
1.
2.
3.
4.
5.
Describe at least two ways that students made
predictions. The evidence supported which method?
Equal amounts of hot water (80oC) are added to cold
water (10oC). Explain how to predict the final
temperature (and then do the math!)
Students performed the experiment, but only measured
a final temp of 40oC Where did the extra heat go?
Predict the final temp of 3 parts 30oC and 1 part 70oC
water.
Did adding equal amounts of metal nails have the same
effect as adding equal amounts of water? What does
this say about heating metal compared to heating
water?
P176
Get a stamp when finished
ENERGY MODEL: SECTION 7
DQ: WHAT IS ENEGY AND HOW IS IT
TRANSFERRED?
p173
5. Temperature is a measure of the average kinetic energy of the
particles that make up the object.
6. The specific heat of a material is a measure of how much
energy is required to heat 1 gram of material 1 degree Celcius.
7. Two objects in contact will reach the same temperature
(equilibrium)
8. 1st Law of thermodynamics: heat = energy + work
9. 2nd Law: Heat is a form of energy and can be transformed
from a warmer object to a cooler object. Heat always flows from
warmer to colder
10. entropy = disorder when heat flows from warmer to colder
entropy (disorder) increases
WHAT FACTORS DETERMINE HOW MUCH HEAT IS
NEEDED TO WARM UP AN OBJECT?
1.)
 2.)
 3.)

p177
What factors determine how much heat needs to
be removed from an object to cool it down?
ENERGY MODEL/PTOGO (P676-677) 1-9
p173
11. A conductor allows heat to flow easily. An
insulator traps heat and does not allow it to flow.
12. Heat energy (Q) is measured by multiplying the
mass (in grams) times the temperature change
times a specific heat constant (the constant for
water is 1 g/C/cal or 4.17 g/C/Joule)
Q=m(Tf-Ti)c
INVESTIGATION #7 REVISITED
p177
Hot nails 37.7C: cold water 21.1C final 22.8C
 How much heat was lost by the nails?
Q=m(Tf-Ti)c
massnails=41g csteel=0.12 g/C/cal
Where did that heat go?
 How much heat was gained by the water?
Q=m(Tf-Ti)c
masswater=41g cwater=1.00 g/C/cal

INVESTIGATION 7
CHECK YOUR UNDERSTANDING
Follow the directions on the handout.
 CU (p672) 1-4/PtoGo (p676) 1-6
p177
 CDP 21-1
 Answer all the questions. Get your notebook
stamped when you are finished.


Notebook check: pages 168-175
PTOGO (P676) 1-6 ANSWERS
1.) 85oC
4.) a) 40oC b) 8360 J = 2000 cal c) -8360 J
5.a) 1620 J
6.a) 1485 J This math is on the Energy Quiz Friday
_________________________________________
7.) 100g
8.a) 60oC
3 TYPES OF ENERGY TRANSFER
CONDUCTION
Energy is transferred by direct contact
 Give an example:

p178
CONVECTION
p178
Energy is transferred by the mass motion of
molecules
 Give an example:

RADIATION
Energy is transferred by electromagnetic
radiation
 Give an example:

p178
ENERGY TRANSFER PROCESSES
p178
The Drinking Bird Lab
So what makes the bird drink?
 Video
 Video explanation
 What NOT to do!
 Answer all the questions
Get a stamp when you finish
Energy Quiz Friday!

GREEN ENERGY
PROJECT
It’s Our Time To Lead
 Global Warming 101
What is Climate Change?
 Bill Nye
 Climate change
reading


Complete page 1
(answers should be in
WHAT IS OUR IMPACT?
Who cares?
 Take Action Now
 Acts of Green. After you
make your list of 10 acts
, choose one to add to the wall
 Pages 2-6 should be finished by Monday (those
who finish all 10 pages by Wednesday April 29
will be rewarded with ice cream! AND you must
complete all 10 pages to have a partner for the
NEXT part of this project…building the houses)

GREEN ACTIVITY PLANNING SHEET (PAGES 3-5)
Describe in detail what you want to do
How is this different from what you do now?
How will this save Energy?
List the steps to complete this activity on the back of this page
Materials list:
Cost
Total cost:
How/when will you consider this activity a success?
GREEN ENERGY PROJECT
Page 7 What energy saving ideas can you build
into your model house? These are probably
different things than you chose for where you
live on page 2
 Finish pages 7-10 (those who finish all 10
pages by Wednesday April 29 will be rewarded
with ice cream! AND you must complete all 10
pages to have a partner for the NEXT part of
this project…building the houses)

HOW MUCH HEAT ENERGY DOES IT TAKE?
p180

Draw 6 water molecules in each box
(remember molecules are always the same
size, only the spacing is different
solid

liquid
gas
Make a statement about the density of water
molecules in each phase
Does it take energy to melt ice?
WHITEBOARD TIME…

Make a line graph to
show the temperature
vs the heat energy of
water. Include these
words: solid ice, liquid,
water vapor(steam),
melting, freezing,
boiling, condensing
T
E
M
P
E
R
A
T
U
R
E
HEAT ENERGY
PHASE CHANGES OF WATER DIAGRAM (WHITE BOOK P459)
p180
Finish
CDP 23-1
23-2
SOLVING PROBLEMS
Phase
1.) How much heat is required
to melt 5 grams of ice?
2.) How much heat is required
to heat 45 g of ice water to 60C?
Heat constant per
gram water
Ice (solid)
Melting ice
to liquid
80
cal/gram
(Liquid)
water
1
4.18
cal/gram joules/g/
/degree degree
Boiling/evap
540
cal/gram
Steam (gas)
3.) How much heat is required by your stomach melt 15
grams of ice and raise the water temperature to 40C?
Does the water change temperature? If yes….Q=mc
If no…..Q=mΔTc
p180
ANSWERS
1.) How much heat is required to melt 5 grams
of ice?
(5 grams)(80 cal/gram) = 400 Cal
2.) How much heat is required to heat 45 g of
water?
(45 grams)(60)(1 cal/gram/degree) = 2700 cal
3.) How much heat is required by your stomach
melt 15 grams of ice and raise the water
temperature to 40C?
(15)(80) = 1200 cal
(15)(1)(40) = 600 cal
total = 1800 calories
WE ALL SCREAM FOR ICE CREAM!
Using only your hands, find the coldest
substance around you…
 How can we remove enough heat to make ice
cream?
p179
 Video
 Follow the directions or your ice cream will not
turn out! Get a stamp when you are cleaned up.
 Answer all the questions and get another
stamp.

SECTION 8: ENERGY CONSUMPTION
(P678-680)

What do you SEE in the cartoon?
p182
WHAT DO YOU THINK?





p182
Use what you see, and your prior experience to answer
these questions in your notebook:
What do we use hot water for?
Most American homes use more energy to heat water
than all the other energy uses combined. There are 2
main types of water heaters. A big tank of water that is
heated by a gas flame (and kept hot until you want to
use it) and “instant” water heaters that use electricity
through an immersion unit to heat water only when
you want to use it.
Which type do you have at home?
Which do you think is more efficient?
INVESTIGATION (P678-680)
DO ALL STEPS 1-5




p182
Assemble a calorimeter using two styrofoam cups on
the base and another as a lid (making holes in the lid
for the thermometer and the immersion heater. Follow
the directions in the book (p679-680)
Make the water at least 25 degrees hotter before you
stop
Answer all the questions and calculations in your
notebook
Get your notebook stamped when you are finished.
ENERGY MODEL: SECTION 8
13. Efficiency of a system = useful energy
output/total energy supplied
14. Electrical energy E = Pt = VIt
15. Electrical energy is measured in kilowatthours
16. 1st Law of Thermodynamics. Energy is
conserved. Energy can be transferred, but is
neither created or destroyed
p173
ENERGY CONSUMPTION (PTOGO P686)
How much energy do you use?
 Follow the directions on the handout. Do all
work in your notebook. The SMUD handouts
stay in this room!
P183 Get a stamp when finished
184


CU p682) 1-4 Get stamped when finished (you
do not have to do the PtoGo questions on the
back…you already did them!)
SECTION 9: COMPARING ENERGY CONSUMPTION
(P691-698)
p185
Heat Coil
Hot Plate
Microwave
Rank the 3 appliances from most efficient to
least efficient.
 Rank the 3 appliances from greatest cost to
heat 1 beaker of water to least cost.
 If high-efficiency appliances cost more, are they
worth the extra cost?

WHICH APPLIANCE IS MOST EFFICIENT?
1.) COPY THE CHART INTO YOUR NOTEBOOK.
p185
Heat coil
Hot plate
microwave
Mass of water
250 grams
250 grams
250 grams
Cold water temp
21.9oC
22.7oC
22.3oC
Appliance power
250 watts
690 watts
650 watts
Heating time
113 sec
2 min
1 min 11 sec
Final water temp
45.4oC
51.4oC
65.1oC
2.) Do you want to change any of your predictions? Give a reason!
3.) Calculate the heat energy for each beaker of water.
4.) Calculate the energy given off by each appliance.
5.) Calculate the efficiency of each appliance.
6.) Which appliance was most efficient?
7.) Assume energy costs $10.40 cents per watt-s and calculate
the cost for each appliance to heat the same beaker of water.
Does this surprise you?
ENERGY MODEL: SECTION 9
p173
17. Heat may be transferred by conduction, convection,
or radiation. Conduction occurs when two objects are
touching each other. Convection occurs through the
movement of a fluid. Radiation occurs when the warmer
object emits electromagnetic waves in all directions and
the cooler object absorbs some or all of it
18. 2nd Law of Thermodynamics. Heat flows from hot to
cold, increasing the disorder by making molecules move
faster (entropy).
19. 3rd Law of Thermodynamics. We can never reach
absolute zero because it is impossible for molecules to
stop moving.
INVESTIGATION
P186
Follow the directions in the book (p691-693)
 Answer all the questions and do the
calculations in your notebook.
 Get your notebook stamped when you are
finished.
 CU (p695) 1-6
 PtoGo (p698) 1-9

UNIT TEST FRIDAY!
Study your quizzes (Electricity and Heat)
 Study your purple model sheets
 Practice by playing jeopardy (on my website)

CH 6 ELECTRICITY FOR EVERYONE
HOUSE PROJECT
Build a scale model house
 Compare energy costs and present on a poster
 Wire your house with simple circuits and light
bulbs
