Thermal Energy Transfer: Conduction, Convection & Radiation
Thermal Energy Transfer: Conduction, Convection & Radiation
Heat always moves from a warmer place to a cooler place.
Place your hand on your desk… Does your desk feel hot or cold? Now take your hand off your desk. Can you feel the warm spot where your hand was?
This is the heat your desk took from you!!!
After switching class periods, have you ever sat in a chair that felt warm??! Ewww!
Why do you think this chair felt warm when you sat on it?
Think about this… If a cup of hot coffee were left sitting in your kitchen at room temperature, what would happen?
The cup of coffee will cool until it reaches room temperature. The Coffee’s heat moved into the air.
If a red popsicle were left sitting in your kitchen at room temperature, what would happen?
The popsicle will melt and then the liquid will warm to room temperature. The heat from the surrounding air moved into the popsicle.
Lets say you have a block of wood and metal that is at room temperature...
72°
72°
Why does metal feel colder than wood, if they are both at the same temperature?
Because metal is a conductor & wood is an insulator.
Feels warmer
Feels colder
Metal is a conductor. It conducts the heat away from your hands. Wood is an insulator. It does not conduct the heat away from your hands as well as the metal. So the wood feels warmer than the metal.
Metals are Conductors With metal atoms, the electrons are free to move around. When the metal is heated, electrons gain kinetic energy and cause the electrons next to it to also gain kinetic energy.
This transfers heat throughout the metal like a domino effect. Insulators, such as wood and plastic, do not have electrons free to move around. This is why they do not conduct heat as well as metals.
The transfer of heat by direct contact of objects.
Conduction Heating a metal strip is an example of conduction. There is direct contact between the particles in the metal bar.
As you heat the metal, the particles vibrate, these vibrations make other particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat.
Remember that gross WARM chair you sat on in your other class???!
The person sitting in the chair before you transferred his/her heat to the cold chair. This is an example of Conduction because the heat transferred with direct contact! Because the chair is plastic and is an insulator … it took a LONG time for that person to sit in that chair to make it warm!
The transfer of heat by electromagnetic waves through empty space.
How does heat energy get from the Sun to the Earth? Outer space is a vacum.
There are no particles between the Sun and the Earth so it CANNOT travel by conduction??
?
Remember Radiant Energy?
The sun provides Visible Energy waves from the electromagnetic spectrum.
The transfer of heat by radiation can transfer through empty space!
Radiation can travel through a vacuum True/False
Radiation requires particles to travel True/False
Have you ever had a sunburn?
How can you get burned from the sun’s energy if you are not in direct contact with the sun?
Radiation does not only come from the sun!
Have you ever sat too close to a campfire while cooking marshmallows– enjoying the warmth- only to notice that your skin is really warm?
Other examples of RADIATION 1. Fire 2. Heat Lamps 3. Sun
The transfer of heat by density changes in a fluid that causes motion.
What is Fluid?
Liquids and Gases are both fluids!
Fluids are a substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; a liquid or gas.
What happens to the particles in a fluid (liquid or a gas) when you heat them?
Cool
Warm
The particles spread out and become Less Dense.
Because the warmer fluid is less dense and the cooler fluid is more dense… Warm
The warmer fluid will rise up
The cooler fluid will sink down
Cool
Have you ever… …noticed that the air near the ceiling is warmer than the air near the floor?
…or that water in a pool is cooler at the deep end? Warmer Water
Colder Water
Convection Current Density changes in a fluid that causes motion!
Cooler water sinks
Cools at the surface
Warmer water rises
Why is it windy at the seaside?
Convection inside the Earth!
Convection currents cause the movement of magma within the earth.
Now that you know about Convection…
Why does hot air rise and cold air sink?
Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air.
Identify the 3 types of heat transfer:
Multiple types of heat transfer can happen at the same time. What 2 types of heat transfers do you see taking place below?
Convection & Conduction
Which of the following is not a method of heat transfer? A.
Radiation
B.
Insulation
C.
Conduction
D.
Convection
In which of the following objects are the particles closest together and most dense? A.
Cold
B.
Cool
C.
Warm
D.
Hot
How does heat energy reach the Earth from the Sun? A.
Radiation
B.
Conduction
C.
Convection
D.
Insulation
Which of the following is the best conductor? A.
Fabric
B.
Plastic
C.
Wood
D.
Iron
Which of the following is the best insulator? A.
Copper
B.
Iron
C.
Wood
D.
Glass
Heat transfers from...?
A.
Hot to Cold
B.
Cold to Hot
If you touched a hot pan, this heat transfer you felt is called... A.
Radiation
B.
Conduction
C.
Convection
D.
Insulation
Where in this picture do you see Conduction?
B A
C
Where in this picture do you see Radiation?
B A
C
Where in this picture do you see Convection?
B A
C
Heat always moves from a warmer place to a cooler place.
Place your hand on your desk… Does your desk feel hot or cold? Now take your hand off your desk. Can you feel the warm spot where your hand was?
This is the heat your desk took from you!!!
After switching class periods, have you ever sat in a chair that felt warm??! Ewww!
Why do you think this chair felt warm when you sat on it?
Think about this… If a cup of hot coffee were left sitting in your kitchen at room temperature, what would happen?
The cup of coffee will cool until it reaches room temperature. The Coffee’s heat moved into the air.
If a red popsicle were left sitting in your kitchen at room temperature, what would happen?
The popsicle will melt and then the liquid will warm to room temperature. The heat from the surrounding air moved into the popsicle.
Lets say you have a block of wood and metal that is at room temperature...
72°
72°
Why does metal feel colder than wood, if they are both at the same temperature?
Because metal is a conductor & wood is an insulator.
Feels warmer
Feels colder
Metal is a conductor. It conducts the heat away from your hands. Wood is an insulator. It does not conduct the heat away from your hands as well as the metal. So the wood feels warmer than the metal.
Metals are Conductors With metal atoms, the electrons are free to move around. When the metal is heated, electrons gain kinetic energy and cause the electrons next to it to also gain kinetic energy.
This transfers heat throughout the metal like a domino effect. Insulators, such as wood and plastic, do not have electrons free to move around. This is why they do not conduct heat as well as metals.
The transfer of heat by direct contact of objects.
Conduction Heating a metal strip is an example of conduction. There is direct contact between the particles in the metal bar.
As you heat the metal, the particles vibrate, these vibrations make other particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat.
Remember that gross WARM chair you sat on in your other class???!
The person sitting in the chair before you transferred his/her heat to the cold chair. This is an example of Conduction because the heat transferred with direct contact! Because the chair is plastic and is an insulator … it took a LONG time for that person to sit in that chair to make it warm!
The transfer of heat by electromagnetic waves through empty space.
How does heat energy get from the Sun to the Earth? Outer space is a vacum.
There are no particles between the Sun and the Earth so it CANNOT travel by conduction??
?
Remember Radiant Energy?
The sun provides Visible Energy waves from the electromagnetic spectrum.
The transfer of heat by radiation can transfer through empty space!
Radiation can travel through a vacuum True/False
Radiation requires particles to travel True/False
Have you ever had a sunburn?
How can you get burned from the sun’s energy if you are not in direct contact with the sun?
Radiation does not only come from the sun!
Have you ever sat too close to a campfire while cooking marshmallows– enjoying the warmth- only to notice that your skin is really warm?
Other examples of RADIATION 1. Fire 2. Heat Lamps 3. Sun
The transfer of heat by density changes in a fluid that causes motion.
What is Fluid?
Liquids and Gases are both fluids!
Fluids are a substance whose molecules move freely past one another and that has the tendency to assume the shape of its container; a liquid or gas.
What happens to the particles in a fluid (liquid or a gas) when you heat them?
Cool
Warm
The particles spread out and become Less Dense.
Because the warmer fluid is less dense and the cooler fluid is more dense… Warm
The warmer fluid will rise up
The cooler fluid will sink down
Cool
Have you ever… …noticed that the air near the ceiling is warmer than the air near the floor?
…or that water in a pool is cooler at the deep end? Warmer Water
Colder Water
Convection Current Density changes in a fluid that causes motion!
Cooler water sinks
Cools at the surface
Warmer water rises
Why is it windy at the seaside?
Convection inside the Earth!
Convection currents cause the movement of magma within the earth.
Now that you know about Convection…
Why does hot air rise and cold air sink?
Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air.
Identify the 3 types of heat transfer:
Multiple types of heat transfer can happen at the same time. What 2 types of heat transfers do you see taking place below?
Convection & Conduction
Which of the following is not a method of heat transfer? A.
Radiation
B.
Insulation
C.
Conduction
D.
Convection
In which of the following objects are the particles closest together and most dense? A.
Cold
B.
Cool
C.
Warm
D.
Hot
How does heat energy reach the Earth from the Sun? A.
Radiation
B.
Conduction
C.
Convection
D.
Insulation
Which of the following is the best conductor? A.
Fabric
B.
Plastic
C.
Wood
D.
Iron
Which of the following is the best insulator? A.
Copper
B.
Iron
C.
Wood
D.
Glass
Heat transfers from...?
A.
Hot to Cold
B.
Cold to Hot
If you touched a hot pan, this heat transfer you felt is called... A.
Radiation
B.
Conduction
C.
Convection
D.
Insulation
Where in this picture do you see Conduction?
B A
C
Where in this picture do you see Radiation?
B A
C
Where in this picture do you see Convection?
B A
C
