Unit C Lesson C10 Thermal Energy: Technology
Completion requirements
Lesson C10: Thermal Energy: Technology
Video Lesson
How do furnaces and boilers work to keep homes warm during the winter? Watch this video to learn more about home heating technologies.
Lesson C10: Thermal Energy: Technology
Figure C.3.10.1β A hot curling iron changes the shape of hair.
Figure C.3.10.2β Heat from a hair dryer can affect the shape of hair.
Heat and Hair
Many people use hair dryers to evaporate water quickly from wet hair. The heat produced by a hair dryer also affects the appearance or style of hair. Hair dryers, curling irons, and hair straightening irons all use heat to change the shape and structure of hair.
Hair strands are made of many particles that connect in particular ways. The connections between particles are called bonds. The bonds in hair strands connect in one type of pattern for straight hair and in another pattern for curly hair.
Heat disrupts the bond patterns in hair. When hair is twisted around a hot curling iron or pulled through a flat hair straightener, heat conducts from the iron to the hair. Heat causes bond patterns in hair to break and form into the desired shape.
Many people use hair dryers to evaporate water quickly from wet hair. The heat produced by a hair dryer also affects the appearance or style of hair. Hair dryers, curling irons, and hair straightening irons all use heat to change the shape and structure of hair.
Hair strands are made of many particles that connect in particular ways. The connections between particles are called bonds. The bonds in hair strands connect in one type of pattern for straight hair and in another pattern for curly hair.
Heat disrupts the bond patterns in hair. When hair is twisted around a hot curling iron or pulled through a flat hair straightener, heat conducts from the iron to the hair. Heat causes bond patterns in hair to break and form into the desired shape.
Reading and Materials for This Lesson:
Science in Action 7
Materials:
Science in Action 7
Reading: Pages 229β232
Materials:
1 large terracotta clay pot, 1 small terracotta clay pot that fits into the first pot, sand, water, modelling clay, piece of cloth to cover the top of the small pot, thermometer, timer
Figure C.3.10.3β Baby incubators keep infants warm.
Figure C.3.10.4β Premature babies live in hospital incubators.
Baby Incubators
Most babies are born after nine months of developing inside their mothers. Some babies are born early and are called premature babies. Premature babies are smaller and more fragile than full-term babies are. They often have health problems because their bodies are not yet fully developed. For this reason, premature babies usually stay in hospital for several months until they grow larger and healthier.
Premature babies have little insulating fat. Their bodies are not capable of regulating body temperature adequately. Premature babies cannot sweat to cool when they are hot, or they cannot shiver to become warm when they are cold. Electric incubators are a technology that help keep babies at appropriate temperatures. Nurses set the temperature in an incubator at a level that provides a baby with exactly the right amount of heat.
Most babies are born after nine months of developing inside their mothers. Some babies are born early and are called premature babies. Premature babies are smaller and more fragile than full-term babies are. They often have health problems because their bodies are not yet fully developed. For this reason, premature babies usually stay in hospital for several months until they grow larger and healthier.
Premature babies have little insulating fat. Their bodies are not capable of regulating body temperature adequately. Premature babies cannot sweat to cool when they are hot, or they cannot shiver to become warm when they are cold. Electric incubators are a technology that help keep babies at appropriate temperatures. Nurses set the temperature in an incubator at a level that provides a baby with exactly the right amount of heat.
Watch More
Non-Electric Baby Incubators
In developing countries, electricity often is not reliable. Electric incubators are not practical in some situations. To solve this problem, some inventors are making baby incubators that are portable, inexpensive, and non-electric.
Watch this video to learn more about a simple portable incubator that keeps babies warm in developing countries.
In developing countries, electricity often is not reliable. Electric incubators are not practical in some situations. To solve this problem, some inventors are making baby incubators that are portable, inexpensive, and non-electric.
Watch this video to learn more about a simple portable incubator that keeps babies warm in developing countries.
An amazing technology for human mobility has been developed recently. An exoskeleton is a frame structure worn on the outside of the body. Exoskeletons can help paralyzed people walk again! Watch this video to see how human exoskeleton technology works.
Refrigerators
Food spoils when bacteria consume it for nutrients. At warmer temperatures, bacteria reproduce rapidly, which spoils food faster. At cooler temperatures, bacteria reproduce slowly, which keeps food fresh longer. Refrigerators allow people to keep food cool and prevent it from spoiling quickly.
Home refrigerators were invented about 100 years ago. Before that, some people cooled food in thick-walled ice houses. During the winter, people filled their ice houses with snow or ice blocks. They covered the ice with insulating straw or sawdust to slow its melting during summer.
Refrigerators are used not only in homes. They are needed to in the transportation of food around the world. Refrigerated trucks, ships, and railroad cars keep food in transport from spoiling.
Food spoils when bacteria consume it for nutrients. At warmer temperatures, bacteria reproduce rapidly, which spoils food faster. At cooler temperatures, bacteria reproduce slowly, which keeps food fresh longer. Refrigerators allow people to keep food cool and prevent it from spoiling quickly.
Home refrigerators were invented about 100 years ago. Before that, some people cooled food in thick-walled ice houses. During the winter, people filled their ice houses with snow or ice blocks. They covered the ice with insulating straw or sawdust to slow its melting during summer.
Refrigerators are used not only in homes. They are needed to in the transportation of food around the world. Refrigerated trucks, ships, and railroad cars keep food in transport from spoiling.
Figure C.3.10.5β Electric refrigerators became common in homes during the 1940s.
Figure C.3.10.6β Refrigerated containers are put on ships.
Watch More
Why Do Fridges Stay Cold?
Watch this animation that explains how refrigerators stay cold.
Watch this animation that explains how refrigerators stay cold.
History of the Fridge
Watch this video to learn who invented the modern refrigerator.
Watch this video to learn who invented the modern refrigerator.
Best Fridge Temperature
This video explains what temperatures are best for slowing harmful bacteria growth.
This video explains what temperatures are best for slowing harmful bacteria growth.
Freon
Before 1990, refrigerators contained a refrigerant called freon. Freon was invented to replace toxic refrigerants such as ammonia and ether in early fridges. Freon is not toxic or flammable.
Before 1990, refrigerators contained a refrigerant called freon. Freon was invented to replace toxic refrigerants such as ammonia and ether in early fridges. Freon is not toxic or flammable.
Freon belongs to a groups of chemicals called CFCs that were used also in air conditioners and aerosol cans.
In the 1980s, scientists noticed a big hole forming in the ozone layer above Antarctica. Ozone is a gas high in the atmosphere that blocks the Sunβs harmful ultraviolet radiation from reaching Earth. People who are exposed to high levels of ultraviolet radiation have increased risk of developing cancer.
Scientists determined that the hole in the ozone layer was caused by increased amounts of CFCs in the atmosphere. Some of the CFCs came from leaky fridges or air conditioners. Now, freon and other CFCs are banned in most places around the world. Since people have stopped using CFCs, the ozone hole has reduced.
Figure C.3.10.9β The ozone layer is located high in Earthβs atmosphere.
Figure C.3.10.7β The back (or sometimes the bottom) of a fridge contains coils filled with refrigerant.
Figure C.3.10.8β Freon was a refrigerant used in refrigerator coils.
Watch More
Ozone Layer
Watch this video to learn more about the ozone layer.
Watch this video to learn more about the ozone layer.
Ozone Hole
The ozone hole over Antarctica is getting smaller. Watch this video to learn why.
The ozone hole over Antarctica is getting smaller. Watch this video to learn why.
Figure C.3.10.10β Clay pots are used to grow houseplants, or to keep food cool without electricity.
Figure C.3.10.11β A clay pot cooler is made of two pots separated by a layer of sand. Photo by
James Emery.
Clay Pot Cooler
Clay pot coolers are used in hot climates to cool food without electricity. Clay pot coolers are made from an inner clay pot (usually with a cloth covering) separated by a layer of damp sand from a slightly larger outer clay pot. The sand contains water that acts as a coolant. Sometimes the sand is covered with leaves or wood chips to keep it moist. Heat transfers from the air inside the pot to the water, causing the water to evaporate. Transferring heat from the inner pot keeps its temperature cool.
An effective water cooler consists of a plastic bag of water inside a larger clay jug with non-drinking water between the bag and the jug. Again, as water evaporates through the outer clay jug, the water within is cooled. The water within the bag remains drinkable, not absorbing anything from the clay jug.
Clay pot coolers are used in hot climates to cool food without electricity. Clay pot coolers are made from an inner clay pot (usually with a cloth covering) separated by a layer of damp sand from a slightly larger outer clay pot. The sand contains water that acts as a coolant. Sometimes the sand is covered with leaves or wood chips to keep it moist. Heat transfers from the air inside the pot to the water, causing the water to evaporate. Transferring heat from the inner pot keeps its temperature cool.
An effective water cooler consists of a plastic bag of water inside a larger clay jug with non-drinking water between the bag and the jug. Again, as water evaporates through the outer clay jug, the water within is cooled. The water within the bag remains drinkable, not absorbing anything from the clay jug.
Try It!
Make a Clay Pot Cooler
Try making your own clay pot cooler, and test how effective it is at keeping food cold.
Materials:
Try making your own clay pot cooler, and test how effective it is at keeping food cold.
Materials:
- 1 large terracotta clay pot
- 1 small terracotta clay pot that fits into the first pot
- sand
- water
- modelling clay
- piece of cloth to cover the top of the small pot
- thermometer
-
timer
Download:
DOWNLOAD this document. It provides a space for you to write answers to questions later in this activity. It also provides a chart for you to record your observations.
Instructions:
DOWNLOAD this document. It provides a space for you to write answers to questions later in this activity. It also provides a chart for you to record your observations.
Instructions:
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If there are holes at the bottom of the clay pots, plug the holes with modelling clay.
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Put sand in the bottom of the large pot. When you put the smaller pot on top of the sand, the tops of both pots should be at the same level.
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Put the smaller pot inside the larger pot.
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Fill the space between the two pots with sand.
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Pour water slowly on the sand. The sand should feel wet. (Donβt drown it!)
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Make the cloth wet. Put the wet cloth over the smaller pot.
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Put the thermometer inside the small clay pot.
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Measure the temperature inside the clay pot. Record this temperature.
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Leave the thermometer inside the clay pot. Measure and record the temperature of the clay pot every 20 minutes for 3 hours. Record the temperatures in a chart such as the following:
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
The water in the sand acts as a coolant. The water absorbs heat from the air inside the smaller pot. Heat transferred from the air causes the water to evaporate and keeps the inner pot cool.
Because the clay pot cooler is made from porous insulating materials of clay and sand, heat transfer into the cool pot is reduced, too.
Because the clay pot cooler is made from porous insulating materials of clay and sand, heat transfer into the cool pot is reduced, too.
Water in the wet cloth absorbs heat from the inner pot and evaporates. The wet cloth helps keep the inner pot cool.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
Unit C Lesson 10 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps β if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here.
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
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REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Self-Check Time!
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Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet β STOP β and go back to step 1 above. Do not look at the answers without first trying the questions.
If the temperature does not drop below 0Λ Celsius, people do not need to heat the entire house to prevent water pipes from freezing and bursting, for example. Warming one room at a time with a space heater saves energy because only the room
being heated uses energy.
Fires must be maintained constantly to continue. Wood or coal must be obtained and stored; ashes must be removed. Heating a home with fuels that are constantly piped in and burned in a furnace or boiler is much more convenient.
Hot air registers are located on the floor to take advantage of convection. When hot air enters a room from the bottom, it rises and heats the entire room quickly. If a hot air register is located on the ceiling, the hot air stays by the ceiling
and warming the room takes longer although a fan to stir the air speeds warming.
Usually, the back of a refrigerator contains refrigerant coils that transfer heat away from the fridge. Some space behind and around the fridge is necessary so that the coils can transfer heat into the air. Then, warm air can move away from
the fridge, keeping the fridge cooler.
Homes heated with furnaces rely on the process of convection. Hot air enters a room through heat registers. Hot air rises, and cool air sinks. Cool air is removed from a room by flowing into return registers. The removal of cool air keeps rooms
warmer and circulates fresh air throughout the house. The furnace fan speeds air circulation, of course.