1. Chapter 3, Lesson 4, Conduction, Convection, and Radiation

2. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 1
*Main Idea
_______________
-What is conduction?
*Thermal energy is transferred by conduction, convection, and radiation.
__________________________________________________
-Conduction is the transfer of thermal energy by collisions between particles in matter.
-When a person burns their fingers from touching a hot pan, it is because the thermal energy from the hot pan is transferred to their cooler skin.

3. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 2
*What are collisions between particles?
-Thermal energy is transferred by conduction.
-When a pot, over a hot fire, receives thermal energy it causes the particles inside to move faster and collide with nearby particles.
-This is an example of conduction.

4. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 3
-What is conduction in solids?
-Conduction transfers thermal energy by collisions of particles.
-In solids, particles are packed closely together which causes collisions to occur when thermal energy is transferred.
-The particles can move back and forth slightly, but they stay in one place because they are next to each other.

5. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 4
*What are conductors?
*Materials in which thermal energy moves quickly are conductors.
*For example, thermal energy moves more than 15,000 times faster in copper than in air,
*Solids usually are better conductors than liquids and gases.
*Metals are the best conductors, which is why cooking pans usually are made of metal.

6. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 5
-What are insulators?
-A material in which thermal energy moves slowly is called an insulator.
-Thermal energy moves slowly in gases because the particles in a gas are so spread apart that collisions occur less often.
-Air is a gas and a good insulator.
-A winter jacket is a good insulator because it is made of materials that trap pockets of air.
-The jacket keeps you warm because the air slows the rate of thermal energy flowing from your body.

7. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 6
*What is convection?
*Convection is the transfer of thermal energy by the movement of matter from place to place.
*For convection to take place, it must occur in a fluid because the particles in solids cannot move from place to place.
*A fluid is a material made of particles that easily can change their locations.
*Liquids and gases are fluids, so convection occurs only in liquids and gases.

8. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 7
-What kind of effect does density have on convection?
-During convection, parts of a fluid that have a higher temperature move to a region where the temperatures of the fluid is lower.
-Convection occurs because of differences in density of a fluid.
-For example, a bottle of soda is heavier than a bottle of air because the density of soda is greater than the bottle of air.
-The bottle of soda has more mass and is heavier.

9. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 8
*What kind of effect does temperature have on density?
*Recall that most materials expand, or take up more space, if their temperature increases.
*Since the mass of the material doesn’t change, and the volume increases, its density decreases when its temperature increases.

10. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 9
-What kind of effect does density have on floating?
-An object sinks if its density is greater than the density of the fluid that surrounds it.
-An object will float if its density is less than the density of the fluid that surrounds it.
-When a hot air balloon expands, due to the heat of the air inside, its air is less dense than the air that surrounds the balloon.
-As a result, the hot air will cause the balloon torise and float into the air.

11. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 10
*What are convection currents?
*A convection current is a circular motion that results from a fluid being heated.
*As warm water rises, it cools and its density increases.
*The cooler, denser water sinks along the sides of a beaker where it may be heated again as it moves towards the bottom of the beaker.

12. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 11
-What is Radiation?
-Radiation is the transfer of thermal energy by electromagnetic waves.
-Unlike conduction and convection, radiation can cause thermal energy to be transferred between objects that aren’t touching.
-You can feel radiation every time the Sun touches your skin.
-At some stores, radiation is used through hot lamps that heat food.
-Electromagnetic waves are used in microwave ovens to heat up food, as well.

13. Chapter 3, Lesson 4, Conduction, Convection, and Radiation, Slide 12
*Summary
*There are three methods of transferring thermal energy:
Conduction is the transfer of thermal energy by the collisions of particles.
Convection is the transfer of thermal energy by the movement of matter from one place to another.
Radiation is the transfer of thermal energy by electromagnetic waves.

14. Questions????
What transfers thermal energy by collisions of particles?
What are the best conductors?
Convection must occur in what type of material?
An object sinks if its density is less than or greater than the fluid that surrounds it?
From which of the three forms of thermal energy (conduction, convection, and radiation), can thermal energy be transferred without touching an object?