The Movement of Heat

1. The Movement of Heat Chapter 4 Lesson 19 TCAP Coach

2. Objectives • SPI: 0507.10.2 Use data from an investigation to determine the method by which heat energy is transferred from one object or material to another.

3. The Movement of Heat • You feel the warmth of the sun on your skin. On a hot day at the beach, the sand feels hot on your feet. On a cold day, the air in your room is warmer near the ceiling than near the floor. • All these things happen because of the movement of heat. • In this lesson, you will learn about the different ways that heat energy can travel.

4. Understanding Heat Energy • As you have learned, all matter is made up of tiny particles that are always moving. • Heat is the energy of these moving particles. • That means heat is kinetic energy. • Your body is warm because tiny particles in it move all the time. • When you move and exercise, the particles that make up your body move a bit faster. That makes your body warmer. • The faster the particles in an object move, the warmer the object will be.

5. Understanding Heat Energy • Heat always flows from a warmer material to a cooler material. • An object becomes hotter if the particles in it start to move faster. • There are three ways this can happen. • They are called conduction, convection, and radiation.

6. Conduction • Picture yourself walking barefoot along a beach on a hot summer day. After walking through the sand for just a little while, your feet feel hot. Heat moves from hot sand to the bottoms of your feet by conduction. • Conduction is the transfer of heat between objects that touch each other. • When two materials have different temperatures, heat energy moves from the warmer one to the cooler one. • In other words, the heat moves from the hot sand to the cooler bottoms of your feet.

7. Conduction • When sand gets hot, the particles that make it up move or vibrate very fast. They have a lot of energy. • When you walk the particles of your skin touch the sand. The particles in the hot sand bump against the particles that make up your feet. • When this happens, the sand particles transfer some energy to your skin. Now your hand has more energy than it had before and it feels hotter.

8. Conduction • Since the sand gave away some heat energy to your feet, the sand is a tiny bit cooler than it was before you walked on it. • The sand transfers energy to your skin until the temperatures of both the sand and your skin are the same. • If your foot stayed in contact with the sand, soon they both would have the same temperature.

9. Conduction • Heating a pot of water on an electric stove is another example of conduction. • Heat moves from the hot coils of the stove to the metal of the pot touching them. • As the bottom of the pot gets hot, heat moves from the bottom of the pot to the cold water that is touching the bottom of the pot.

10. Conduction

11. Convection • How does water in a pot on a stove get hot all over? • Remember, the water at the bottom of the pot is heated by conduction. Some heat moves through the rest of the water by conduction, as particles bump into each other and transfer energy. • But the water is also heated by convection. • Convection is the transfer of energy through a liquid or gas by means of currents.

12. Convection • Think again about the pot of water on the stove. The water on the bottom of the pot is in contact with the metal of the hot pot, so conduction occurs. This bottom layer of water heats up because it touches the metal pot.

13. Convection • Warm water is less dense than cool water. You learned about density in Lesson 16. • This difference in density makes warmer water rise in the pot. • Cool water is denser than warm water. This makes cool water sink in the pot. • As cooler water reaches the bottom, it heats up and rises.

14. Convection • Water up at the top is now cooler than the water below, so it begins to fall. • This constant rising and falling of warm and cool water makes convection currents. • Convection currents transfer heat throughout the water. • Convection currents also warm your room. As air near a radiator or a vent is heated, the air rises toward the ceiling. Then the air cools and sinks. This happens over and over, spreading heat throughout your room.

15. Convection

16. Convection • Convection currents also move heat through Earth’s atmosphere. • Cold air sinks because it is denser, and warm air rises because it is less dense. • This ongoing cycle produces currents of moving air, which we call winds. • Convection is responsible for much of Earth’s weather.

17. Convection

18. Radiation • In both conduction and convection, particles of matter transfer heat energy. • The particles can be in a solid, such as the bottom of a pot. • They can be in a liquid, such as the water in the pot. • Or they can be in gases, such as the air in your room or in Earth’s atmosphere. • However, heat can also be transferred through empty space.

19. Radiation • The transfer of heat through space is called radiation. • That is how heat from the sun, which is millions of kilometers from Earth, reaches your skin. • The sun’s energy travels as waves through space. • When the energy in sunlight reaches your skin, the energy makes particles in your skin move faster. • This movement increases the temperature of your skin, and you feel the sun’s warmth.

20. Radiation

21. 1. Which kind of heat transfer takes place when you put a spoon in a cup of soup and the spoon gets hot to the touch? • A. convection • B. conduction • C. temperature • D. radiation

22. 1. Which kind of heat transfer takes place when you put a spoon in a cup of soup and the spoon gets hot to the touch? • B. conduction

23. 2. Which kind of heat transfer can take place through space? • A. radiation • B. conduction • C. convection • D. temperature

24. 2. Which kind of heat transfer can take place through space? • A. radiation

25. 3. Which kind of heat transfer causes wind? • A. radiation • B. conduction • C. temperature • D. convection

26. 3. Which kind of heat transfer causes wind? • D. convection

27. 4. When sand is heated by the sun, which kind of heat transfer is this? • A. conduction • B. temperature • C. radiation • D. convection

28. 4. When sand is heated by the sun, which kind of heat transfer is this? • C. radiation