Unit C Lesson C5 Heat Transfer Conduction
Completion requirements
Lesson C5: Heat Transfer: Conduction
Video Lesson
Heat transfers from place to place in specific ways. Watch this video to learn how heat transfers by direct contact, and how that heat transfer can be prevented.
Lesson C5: Heat Transfer: Conduction
Figure C.2.5.1– Fire-walking involves walking barefoot on hot coals.
Figure C.2.5.2– Fire-walking is a tradition in many countries.
Fire-Walking
Many cultures practise fire-walking as a traditional ceremony. Fire-walkers walk barefoot quickly over a bed of hot coals. How do people walk on hot coals without burning their feet?
The answer involves how heat transfers from the hot coals to people’s feet through conduction. Fire-walkers move quickly so that their feet never touch the hot coals for long. Without much contact with the coals, heat cannot conduct from the coals to a fire-walker’s feet. Also, fire-walkers do not walk directly on red-hot embers. They walk on white charcoal covering the embers. Charcoal is a poor conductor of heat, which means it does not transfer heat quickly to the skin. This also prevents fire-walkers from being burned.
Reading and Materials for This Lesson
Science in Action 7
Materials:
Science in Action 7
Reading: Pages
Materials:
butter, large metal spoon, large plastic cooking spoon, wooden spoon, bowl, hot tap water, 2 small plastic sandwich bags, shortening such as Crisco, 2 bowls, cold water, 12 ice cubes, timer
Watch More
Fire-Walkers
Watch this video to see a fire-walking ceremony in Japan.
Watch this video to see a fire-walking ceremony in Japan.
The Science of Fire-Walking
Watch this video to learn more about how scientific knowledge about heat explains fire-walking.
Watch this video to learn more about how scientific knowledge about heat explains fire-walking.
Cooking Pots
Cooking pots usually are made of metal because metals are good conductors of heat. However, not all cooking pots are made of the same type of metal. Various types of metal have various characteristics, each with advantages and disadvantages as cooking pots.
Cooking pots usually are made of metal because metals are good conductors of heat. However, not all cooking pots are made of the same type of metal. Various types of metal have various characteristics, each with advantages and disadvantages as cooking pots.
Cast iron pans are very heavy and sturdy. Iron conducts heat slowly, but it holds heat very well. Cast iron is very good for cooking food slowly at low temperatures. Cast iron has a naturally non-stick surface. However, cast iron pans are heavy and can
be very difficult to lift. If they are not cared for properly, they can rust.
Both copper and aluminum cooking pots conduct heat well. Copper is especially good at conducting heat quickly and cooking food evenly. Copper pots are usually much more expensive than aluminum pots are. However, both copper and aluminum react chemically with acidic foods such as citrus and vinegar. For this reason, copper pots often are lined with a non-reactive metal.
Many people use stainless steel pots because they are inexpensive and non-reactive with food. However, stainless steel does not conduct heat as quickly as copper and aluminum do. Some stainless steel pots have a copper or aluminum layer in the base of the pot. This helps conduct heat to food faster while keeping the pot non-reactive.
Both copper and aluminum cooking pots conduct heat well. Copper is especially good at conducting heat quickly and cooking food evenly. Copper pots are usually much more expensive than aluminum pots are. However, both copper and aluminum react chemically with acidic foods such as citrus and vinegar. For this reason, copper pots often are lined with a non-reactive metal.
Many people use stainless steel pots because they are inexpensive and non-reactive with food. However, stainless steel does not conduct heat as quickly as copper and aluminum do. Some stainless steel pots have a copper or aluminum layer in the base of the pot. This helps conduct heat to food faster while keeping the pot non-reactive.
Figure C.2.5.3– Copper cooking pots are expensive, but they cook food evenly.
Figure C.2.5.4– Cast iron pans are heavy and non-stick.
Figure C.2.5.5– Aluminum cooking pots are effective at conducting heat.
Try It!
Best Conductor
Which material is the best conductor of heat and will melt butter the fastest? Try this simple experiment.
Materials:
Which material is the best conductor of heat and will melt butter the fastest? Try this simple experiment.
Materials:
- butter
- metal spoon
- plastic spoon
- wooden spoon
- bowl
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hot tap water
Try to choose three spoons that are about the same size.
Instructions:
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Fill the bowl half full with hot tap water.
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Place the handles of all three spoons in the bowl, propping up the spoons against the edge of the bowl. (Yes, the spoons are backwards with handles down and spoons up!)
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Cut three small pieces of butter of equal size. The butter should fit on the spoons.
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Place one piece of butter on each spoon.
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Observe the spoons.
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 metal spoon melted butter the fastest. Metal is a good conductor of heat. The particles in the metal transferred heat energy quickly to the butter.
The plastic spoon melted butter the slowest. Plastic is a poor conductor of heat. The particles in plastic transferred heat energy slowly to the butter.
Figure C.2.5.6– Some whales have a blubber layer that is almost 50 cm thick!
Figure C.2.5.7– Seals live in cold climates.
Blubber
Warm-blooded mammals in cold climates need insulation to stop heat conduction away from their bodies. Many cold-climate mammals have blubber in their bodies as insulation. Whales, dolphins, walruses, polar bears, and seals are mammals with blubber. Blubber is very important for these animals that live and hunt for food in cold ocean water.
Blubber is a thick layer of fat under the skin. Fat does not conduct heat well. In addition, blubber stores nutrients for animals to use when they cannot find food. Blubber helps animals to float in water, too.
Figure C.2.5.8– Walruses are Arctic mammals that live both on land and in water.
Try It!
Blubber Glove
Try this simple experiment to test how fat acts as an insulator.
Materials:
Try this simple experiment to test how fat acts as an insulator.
Materials:
- 2 small plastic sandwich bags
- shortening such as Crisco
- 2 bowls
- cold water
- 12 ice cubes
-
timer
Instructions:
-
Fill both bowls half-full with cold water.
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Add 6 ice cubes to each bowl.
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Fill 1 plastic bag half-full with shortening.
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Put your hand inside the second plastic bag.
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Put your bag-covered hand into the plastic bag of shortening. Move the shortening around so that your hand is covered completely with shortening. Add more shortening if you need it.
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Start the timer.
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Stick your shortening-covered hand into one bowl of ice water and your other bare hand into the other bowl of ice water.
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Measure how long you can keep each hand in the ice water without feeling uncomfortable.
Questions:
Think about the following question very carefully. Then, type or write your answer. After you have your answer, click the question for feedback.
Think about the following question very carefully. Then, type or write your answer. After you have your answer, click the question for feedback.
Shortening is a type of fat. Fat is a good insulator. The shortening glove stopped heat conduction from your hand to the ice water. The fat layer allowed you to keep your hand in the ice water longer than the uncovered hand could be.
Blubber is a type of fat, which means it is a good insulator. Blubber stops heat conduction from animal bodies to cold ocean water. A blubber fat layer allows mammals to stay in cold ocean water longer.
Blubber is a type of fat, which means it is a good insulator. Blubber stops heat conduction from animal bodies to cold ocean water. A blubber fat layer allows mammals to stay in cold ocean water longer.
Figure C.2.5.9– Temperature sensors in your skin tell you that something is hot.
Figure C.2.5.10– Temperature sensors in your skin send messages to your brain when you touch something cold.
Sensing Temperature
To avoid burning or freezing your skin, your body must sense when something is too hot or too cold to touch safely. Your skin contains special temperature sensors. When you touch something extremely hot or cold, the temperature sensors in your skin send messages to your brain to tell you to move away.
Heat has to conduct to your skin for your temperature sensors to be activated. If you touch an object that is a good conductor, heat transfers quickly between the object and your skin. You will sense the temperature of the object quickly. If you touch an object that is a poor conductor, heat transfers slowly between the object and your skin.
To avoid burning or freezing your skin, your body must sense when something is too hot or too cold to touch safely. Your skin contains special temperature sensors. When you touch something extremely hot or cold, the temperature sensors in your skin send messages to your brain to tell you to move away.
Heat has to conduct to your skin for your temperature sensors to be activated. If you touch an object that is a good conductor, heat transfers quickly between the object and your skin. You will sense the temperature of the object quickly. If you touch an object that is a poor conductor, heat transfers slowly between the object and your skin.
Try It!
Temperature of Conductors and Insulators
Try this simple experiment to see if you sense the temperature of conductors and insulators differently.
Try this simple experiment to see if you sense the temperature of conductors and insulators differently.
Materials:
- metal cookie sheet
- thin book
- fridge
Instructions:
-
Put the metal cookie sheet and the book into the fridge for 3 hours.
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Take both objects from the fridge. Both objects will have the same temperature because they have been in the same environment.
- Hold the metal cookie sheet in one hand and the book in the other hand. Which object feels colder?
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 5 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – 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 – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
The particles in the electric stove burner transfer heat energy to the frying pan. (Or, if a gas flame is used, the heat is transferred directly to the frying pan.) The fast vibrating particles in the stove burner transfer heat energy to the
slower vibrating particles in the frying pan base. Then, the particles in the frying pan base transfer their heat energy to other nearby particles in the frying pan. Eventually, heat energy conducts to the particles in the frying pan handle.
A glove or oven mitt will insulate your hand from the metal frying pan handle.
Heat from a clothing iron conducts to the surface under the iron. If a hot clothing iron is left on a surface fabric face-down, heat energy transfers continuously from the iron to the surface. If the surface under the iron is wood or fabric,
it can gain enough heat energy to catch fire.
The empty vacuum space in a Thermos acts as an insulator. Very few air particles are in the vacuum layer of the Thermos to conduct heat away from the inner container if the contents are hot or to the inner container if the contents are cold.
Because heat does not conduct quickly to or from the outer layer, liquid inside a Thermos stays at its original temperature for a long time.
Steel is a type of metal, which means it is a good conductor. The steel in the toe of the boots conducts heat quickly away from a person’s toes. This makes a person’s feet feel colder more quickly.
The Pacific Ocean near Canada is cold all year round. Wetsuits are made of insulating materials. Wetsuits help slow the conduction of heat from a surfer’s body to the cold ocean water.