Download Science 9th grade LEARNING OBJECT How is heat transferred

Science 9th grade
LEARNING UNIT
How are the components of
the world related?
S/K
Language
Socio cultural context of
the LO
Curricular axis
Standard competencies
Background Knowledge
English Review topic
Glossary
Vocabulary Box
LEARNING OBJECT
How is heat transferred?
SKILL 1. Give examples and illustrate processes of heat
transfer by means of conduction, convection and radiation.
SKILL 2. Explain transfer of thermic energy by means of
conduction through molecular collision.
SKILL 3. Assess the process of heat transfer by means of
convection.
SKILL 4. Explain the formation of gusts in the atmosphere.
SKILL 5. Research into the conditions that would allow a
more efficient accumulation of wind power form the
environment.
English
Colombia
Physical Surroundings
Explain conditions of change an conservation in multiple
systems taking into account transfer and transport of
energy and its interaction with matter.
Temperature, heat, specific heat, thermal expansion,
pressure, flow behavior, density, Archimedes´ principle.
WH- particles (When, Where, What, Who, Which)
 Joule: Measurement unit of energy, which corresponds
to one Kilogram per square meter per square second.
 Calorie: Measurement unit of heat, equal to the
amount of heat necessary to increase 1°C to 1 gram of
water.
 Combustion: Chemical reaction produced between
oxygen and an oxidizable material, in conjunction of
energy release, normally manifested by incandescence
or flame.
 Infrared: Radiation with lower frequency than visible
light.
 Microwave: Radiation with lower frequency than
infrared.
 Conductor: Material or object that allows the
transmission of heat or electricity through its mass.
 Bare: Without covering or clothing; naked; nude
 Device: A thing made for a particular purpose; an
invention or contrivance, specially a mechanical or
electrical one.
 Gust: A sudden, strong blast of wind.
 Landscape: A section or expanse of rural scenery,
usually extensive, that can be seen from a single
viewpoint.



Leisure: Time free from the demands of works or duty,
when one can rest; enjoy hobbies or sports, etc.
Trade wind: Any of the nearly constant easterly winds
that dominate most of the tropics and subtropics
throughout the world, blowing mainly from the
northeast in the Northern Hemisphere, and from the
southeast in the Southern Hemisphere.
Upend: To set on end, as a barrel or ship.
Terms retrieved from the website www.dictionary.com
NAME: _________________________________________________
GRADE: ________________________________________________
Introduction
Colombia is a privileged country in many aspects, one of them being located in an area with
plenty solar energy all year round.
You are in constant energetic transfer with your surroundings; sometimes you get energy from
the environment and in other occasions the environment receives energy from you.
Have you ever wondered why you feel so cold in cities like Bogota, and so hot in places like
Barranquilla? And how does world over-population has an effect on global warming?
These and other questions may be answered as you dig deeper in the topics covered in this
learning unit.
Come, have fun and learn!
Objectives
1. To establish differences between processes of heat transfer by means of conduction,
convection and radiation.
2. To describe every-day situations based on heat transfer.
3. To appraise the impact of clean energies like wind power.
Activity 1
SKILL 1. Give examples and illustrate processes of heat transfer by means of conduction,
convection and radiation.
SKILL 2. Explain transfer of thermic energy by means of conduction through molecular
collision.
Heat (Q)
Heat is the energy transferred from a body with more temperature to another with less
temperature. Bodies gain or lose heat, but it is incorrect to say that a body possesses heat, as
well as stating that a body transfers temperature to another body.
Figure 1. Heat
Heat is transferred from a body with more temperature to another with less temperature.
Measurement of heat: Heat is not only capable of raising the temperature of bodies, but can
also move them and apply force to them. The units to measure heat are Calories and Joules.
The heat supplied to a substance is directly proportional to the increase in temperature ( T ),
to the mass (m) of the substance and the material, represented by the specific heat (c).
Therefore:
Q  m  c  T
Specific heat (c): The amount of heat that must be supplied to a gram of a given substance
to increase its temperature one Celsius degree.
Specific heat of some
substances
Substanc Cal/ J/K
e
g ºC g ºK
Water
1
4186
Air
0.24 1003
Ethyl
0.6
2511
alcohol
Aluminum
0.22
920
Copper
0.09
376
Ice
0.53 2215
Iron
0.12
502
Mercury
0.03
126
Remember that
The equivalence between Joules (J) and Calories (Cal) is 4.18 J per each calorie.
Heat transfer
Heat flows spontaneously from a system with more temperature to the one with less
temperature. The average temperature of the human body is 37°C, and heat transfer occurs
depending on the geographic location and the temperature of the environment. Figure 2 shows
four cases of heat transfer in different places on Earth.
Place: BucaramangaColombia
Room temperature: 23°C
Q transferred by the human
body
(a)
Place: Sahara Desert
Room temperature: 50°C
Place: BarrancabermejaColombia
Room temperature: 37°C
Q=0
(b)
Place: South Pole
Room temperature: -40°C
Q que absorbe el cuerpo
Q transferred by the human
humano
body
(c)
(d)
Figure 2. Heat transfer between the environment and the human body. Retrieved from:
http://www.matematicasypoesia.com.es/juegosOL/para-pintar/ninios-saltando.jpg and
modified by author.
In an environment with a temperature lower than body temperature, heat is transferred from
the human body to the environment (Figures 2a and 2d); in an environment with higher
temperature, heat is transferred from the environment to the human body (Figure 2c). Finally,
there is no heat transfer if the temperature of the environment is equal to the heat of the
body, which means that there is heat balance (Figure 2b).
In the South Pole there is so much heat transfer, that a “cold sensation” occurs and a thermal
isolator must be used to protect the body in order to avoid heat transfer to the environment.
Types of Heat Transfer

Conduction: The heat transferred by the source makes the particles vibrate with a higher
frequency, colliding with others and transferring kinetic energy. This means that heat is
conducted by successive collisions between particles, exchanging kinetic energy between
microscopic particles (molecules, atoms and electrons) in which the less energetic particles
gain more energy from more energetic particles. (Figure 3)
Figure 3. Conduction of heat
The heat conducted by combustion of the candle is scattered through the entire rod, making
the wax holding the paper clips melt.
Retrieved from: http://www.uruguayeduca.edu.uy/Userfiles/P0001/File/conduccion_2006.swf
Convection: Is the transmission of heat through actual movement of the molecules in a
substance. This phenomenon can only occur in fluids in which by means of natural movement
(differences in density) or forced circulation (with help of ventilators, pumps, etc.) the particles
may move around, transporting heat without interrupting the physical continuity of the body.
(Figure 4)
Figure 4. Convection
The hot fluid ascends and the cold fluid descends, forming convection currents.
Retrieved from: http://cbtis37fisica2.blogspot.es/1409874665/transferencia-de-calor/

Radiation: The transmission of heat between two bodies trough electromagnetic waves,
without contact or connection of any kind of material. (Figure 5)
Figure 5. Radiation
Electromagnetic waves travel from the Sun and heat the Earth.
Retrieved from: https://delatorresteffani.files.wordpress.com/2014/04/radiacion.jpg
Remember that
Temperature expresses the level of agitation of the particles of matter.
Examples of Heat Transfer
1. In the kitchen: When we place a pot full of water on the stove, the pot gains heat by
conduction, the water by convection and the air surrounding the pot by radiation. (Figure 6)
2. Solar panel: The heat reaches the panel from the Sun through radiation. If an object is
placed on top of the panel, the heat will be transferred by conduction. (Figure 7)
3. Microwave oven: Electrons located in higher energetic levels inside the atom fall to lower
levels, releasing electromagnetic radiation of the same frequency as the microwaves, which
are absorbed by the food inside the oven and increasing its temperature.
4. Floor and carpet: When placing your bare foot on a ceramic tile on the floor, it feels colder
than placing them on the rug found in the same room. This happens because heat
conduction occurs faster in the ceramic tile, being a better heat conductor. (Figure 9).
Did you know that…?
Metals are good heat and electricity conductors.
5. Radiator: Inside a house, the radiator heats the air through radiation; this hot air ascends
while the cold air descends to be heated again by the radiator, generating convection
currents. (Figure 10)
6. Flight in air glider: Convection currents are used to ascend with warm gusts and descend
with cold gusts. Air-gliding is impossible at night because there is no solar radiation to heat
the air. (Figure 11)
7. Refrigerator: Convection currents are generated inside a refrigerator when cold air
descends and makes food transfer heat to air around it, heating it and making it ascend so
it gets cold, descending and starting the cycle once again. (Figure 12)
Did you know that?
The Andean Condor (Vultur gryphus), ensign bird of Colombia, spends hours flying without the
need of flapping its wings, thanks to convection currents in the atmosphere.
Learning Activity 1
The following activity will help you to reinforce the concepts related to conduction, convection
and radiation.
1. Match the concepts by connecting them with a line.
Type of heat transfer
Radiation
Conduction
Convection
Example
Heating a metallic rod by
revolving the burning log in a
grill.
Cooling
a
room
with
air
conditioning systems.
Maintaining biscuits warm with a
glowing light bulb in a cafeteria.
2. Fill in the blanks:
A. During heat propagation by means of _______________, molecules collide, exchanging
kinetic energy.
B. During conduction, molecules receive energy and ____________ faster.
C. During conduction, there is no movement of ______________.
Activity 2
SKILL 3. Assess the process of heat transfer by means of convection.
SKILL 4. Explain the formation of gusts in the atmosphere.
Convection in the atmosphere
Convection is a process that occurs naturally in the atmosphere; in the morning the Sun heats
up the surface of the Earth, which transfers heat through conduction and infrared radiation to
the air next to it. The air warmed by the surface of the Earth expands and ascends because it
has a lighter density and leaves room for masses of colder air to descend and warm up with
the heat of the surface, completing the cycle. Convection currents are formed in the
atmosphere, and these can be faster or slower depending on the difference of temperatures
between the air masses and the surface of the Earth, as well as the composition of the soil,
different types of rocks, grass, sand, among other factors; reason why the amount of heat
absorbed from the Sun can vary. (Figure 13).
Figure 13. Convection currents in the atmosphere, generating formation of gusts.
Retrieved from: http://latierraysuscomponentes.blogspot.com.co/
Colombia has countless numbers of places where atmospheric convection is used for leisure
activities, such as para-gliding. One of the most important zones is located near the
Chicamocha canyon because its geography and landscapes make it an ideal place for this type
of activity.
The Earth is oval-shaped and its rotation axis has an approximate inclination of 23°. This
causes that some areas receive more solar radiation that others, generating seasons.
Equatorial regions, better known as “tropics”, receive more heat from the Sun than polar
regions, and because of this, convection zones of warm air towards the poles, and cold air
towards the equator are generated.
During some periods of the year, drastic differences of temperature, among other factors,
create hurricanes and tornadoes, due to faster and harsher convection currents. (Figure 16).
Figure 16. Hurricane formed by sudden movements of winds caused by convection.
Very important!
Because of inclination of the rotation axis of Earth, Colombia, which is located in a tropical
zone, receives solar radiation all year long, reason why there are no seasons.
Learning activity 2
This activity will help you focus on the mechanism of heat transfer by convection.
Experiment!
Follow these steps to complete the experiment. To do so, you will need transparent glasses, a
sheet of plastic that should be slightly bigger than the rim of the glasses, food colorants, hot
water and cold water.
1. Fill one glass with hot, colored water and the other glass with cold water without
colorant, as shown in the next figure:
2. Now, place the plastic sheet covering the glass of cold water.
3. Very carefully, upend the glass with cold water and place it on top of the other glass.
4. Remove the sheet between the glasses, making sure the glasses do not move and are
perfectly lined with the each other.
5. Watch what happens, and based on it, complete the following sentence.
The colored water _________ and the cold water _________ until they mix, so that after a
while, the entire water is _____________ in thermal balance.
Activity 3
SKILL 5. Research into the conditions that would allow a more efficient accumulation of wind
power form the environment.
Wind Turbine
A wind turbine is a device that transforms the energy from the movement of the wind into
electric energy by using generators.
1. Rotor blades: Capture the wind and transfer their power to the multiplier. Are
approximately 20 meters long.
2. Multiplier: Generates 50 times the revolutions of the rotation axis.
3. Generator. The multiplier axis is connected to the generator, which transfers the rotation
mechanical energy into electric energy.
4. Vane and anemometer: Indicate the strength and direction of the wind.
5. Alternator: Converts continuous current into alternate current.
6. Transformer: Converts the voltage into an adequate value for distribution.
7. Electric lines: Transport electric current.
Did you know that? Colombia generates only 0.12% of energy through wind farms.
Jepirachi Wind Farm
Jepirachi was the first wind farm built in Colombia, in the year 2004. It is located in the La
Guajira department, in the north-east region of the country, very close to Cabo de la Vela, a
touristic attraction. (Figure 18).
It counts with 15 wind turbines of 1.3 megawatts each, which capture trade winds coming all
year long through the region at an average speed of 9.8 m/s. The turbines are distributed in
two rows, in an area of about 1 km long, parallel to the beach, and 1.2 km wide.
Figure 18. Jepirachi, wind farm in Colombia.
Retrieved from: http://www.renunciamosyviajamos.com/galeria/parque-eolico-de-la-guajiralos-gigantes-de-energia-en-medio-del-desierto/
Did you know that?
Jepirachi means “winds from the north-east” in Wayuunaiki, the native language of the Wayuu,
one of the most important indigenous populations in Colombia.
Learning Activity 3
This activity will help you reinforce the knowledge about the benefits of wind power.
Solve the following crossword puzzle.
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p
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g
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t
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w
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Clues:
1.
2.
3.
4.
5.
Name of the first wind farm in Colombia.
Energy obtained from the wind.
Part of the wind generator that multiplies the number of revolutions.
Transforms mechanical energy into electric energy.
Indicates direction of the wind.
6. Modifies the value of the voltage so it can be distributed through electric lines.
Summary.
Homework
The following activity allows you to reinforce your knowledge about heat transfer. To do so,
you must have studied and understood all the topics covered in activity 1
1.
2.
3.
4.
5.
Work with two classmates and analyze sources of heat found in the kitchen of your house.
Make a list of all the elements that transfer heat to the environment of your kitchen.
Draw in your notebook a sketch of your kitchen and the location of these objects.
Analyze each heat source and how they transfer energy to the environment.
Share your results with the rest of your class through a presentation and compare your
information with the other groups.
Evaluation
The objective of the following evaluation is to review the different mechanisms of heat transfer
and their applications in wind power. Topics that were covered during the development of this
Learning Object. To do so, it is crucial that you reviewed each activity, understood the
suggested resources and completed the learning activities.
I.
Answer True (T) or False (F) correspondingly.
1. Cooling a room with air conditioning is an example of convection. ( )
2. Cyclones or tornadoes in a storm occur due to conduction. ( )
3. Heating of a metallic spoon used to stir hot soup occurs due to radiation. (
)
4. Heat transfer by radiation needs particles of matter to transport energy. (
5. In collisions between the molecules of an object, energy transfer occurs. (
II.
)
)
Fill in the blanks with the correct information related to heat transfer.
1. A person located in Bogota, where the room temperature is 9°C, __________ heat to
the environment.
2. A very cold glass of water is located on the table of a room where the temperature is
25°C, therefore the glass of water __________ heat from the environment.
3. Two ice cubes with the same temperature are in contact with each other, therefore they
are found in thermal _________.
Bibliography
CBTIS
37
Física
2.
Transferencia
de
calor.
http://cbtis37fisica2.blogspot.es/1409874665/transferencia-de-calor/
Retrieved
from:
E-ducativa. Gobierno de Aragón. La propagación del calor. Retrieved from:
http://educativa.catedu.es/44700165/aula/archivos/repositorio/500/518/html/Unidad_02/pagina_13.h
tml
Endesa
educa.
(2014).
Generación
eléctrica.
Retrieved
http://www.endesaeduca.com/Endesa_educa/recursos-interactivos/produccion-deelectricidad/xiii.-las-centrales-eolicas
from:
Fluidos y Ondas. Escuela Colombiana de Carreras Industriales.
Transmisión de Calor.
Retrieved from: https://delatorresteffani.files.wordpress.com/2014/04/radiacion.jpg
Renunciamos
y
viajamos.
Parque
eólico
de
la
Guajira.
Retrieved
from:
http://www.renunciamosyviajamos.com/galeria/parque-eolico-de-la-guajira-los-gigantes-deenergia-en-medio-del-desierto/
Revista de Investigación en ciencias y Matemáticas. (2006). Corrientes Oceánicas. Retrieved
from: http://cremc.ponce.inter.edu/2daedicion/articulo2.htm
Romero, O., Rincón, L. (2008), Nueva Física 11. Bogotá: Santillana.
Serway, R.,Jewett, J. (2009). Física para ciencias e ingeniería Volumen 1. Retrieved from:
https://deymerg.files.wordpress.com/2013/07/fc3adsica-para-ciencia-e-ingenierc3ada_serway-7ed-vol1.pdf
Sophimania.
¿Qué
ondas
con
el
microondas?.
Retrieved
from:
https://sophimania.pe/ciencia/medicina-salud-y-alimentos/que-ondas-con-:el-microondas-laverdad-sobre-su-mentada-relacion-con-el-cancer/
Trabajo
de
Ámbito
Científico.
(2014).
Dinámica
http://latierraysuscomponentes.blogspot.com.co/
atmosférica.
Retrieved
Uruguay
Educa.
(2009).
Centro
de
recursos.
Retrieved
http://www.uruguayeduca.edu.uy/Userfiles/P0001/File/conduccion_2006.swf





from:
from:
Joule: Measurement unit of energy, which corresponds to one Kilogram per square meter
per square second.
Calorie: Measurement unit of heat, equal to the amount of heat necessary to increase 1°C
to 1 gram of water.
Combustion: Chemical reaction produced between oxygen and an oxidizable material, in
conjunction of energy release, normally manifested by incandescence or flame.
Infrared: Radiation with lower frequency than visible light.
Microwave: Radiation with lower frequency than infrared.
Glossary

Conductor: Material or object that allows the transmission of heat or electricity through its
mass.
Vocabulary Box






Bare: Without covering or clothing; naked; nude
Device: A thing made for a particular purpose; an invention or contrivance, specially a
mechanical or electrical one.
Gust: A sudden, strong blast of wind.
Landscape: A section or expanse of rural scenery, usually extensive, that can be seen from
a single viewpoint.
Leisure: Time free from the demands of works or duty, when one can rest; enjoy hobbies
or sports, etc.
Trade wind: Any of the nearly constant easterly winds that dominate most of the tropics
and subtropics throughout the world, blowing mainly from the northeast in the Northern
Hemisphere, and from the southeast in the Southern Hemisphere.
Upend: To set on end, as a barrel or ship.
Terms retrieved from the website www.dictionary.com
English Review Topic
WH- particles (When, Where, What, Who, Which)