How is heat (thermal energy) transferred? 6.P.3.1 Energy can be transferred from one system to another (or from a system to its environment) in different ways thermally, when a warmer object is in contact with a cooler one mechanically, when two objects push or pull on each other over a distance electrically, when an electrical source such as a battery or generator is connected in a complete circuit to an electrical device by electromagnetic waves 2

A hot cup of cocoa is left on the kitchen counter A hot cup of cocoa is left on the kitchen counter. A bowl of ice cream is left on the dining room table. Describe what happens to both, and explain in terms of “thermal energy” and the motion of atoms.

How is Heat Transferred? Heat is transferred in three ways: 6.P.3.1 Heat flows through materials or across space from warm objects to cooler objects, until both objects are at equilibrium. Heat travels through solids, primarily by conduction. Heat is circulated in fluids, both liquids and gases, through the process of convection. Radiation is energy that travels across distances in the form of electromagnetic waves. Over time, thermal energy tends to spread out through a material and from one material to another if they are in contact (conduction). Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection 4

Thermal Energy Transfer 6.P.3.1 Heat travels through solids, primarily by conduction. Over time, thermal energy tends to spread out through a material and from one material to another if they are in contact (conduction). CONDUCTION: heat transferred when two objects touch. (works best in solids) 5

Thermal Energy Transfer: Conduction Conduction works better in solids (such as land and metals), but not as well in liquids and gases (air and water do not conduct heat as well.) 6.P.3.1 Heat travels through solids, primarily by conduction. Over time, thermal energy tends to spread out through a material and from one material to another if they are in contact (conduction). 6

Conduction Ex. #2 Conduction Ex. #3 Conduction Ex. #1 Examples of conduction where heat is transferred from particle to particle. How is the thermal energy being transferred in each picture? Conduction Ex. #2 Conduction Ex. #3 Conduction Ex. #1 the heat is transferred from the frying pan to the cooking egg the heat is transferred from the hot coffee to the spoon the heat is transferred from the feet to the cold tile floor 6.P.3.1 Heat travels through solids, primarily by conduction. Over time, thermal energy tends to spread out through a material and from one material to another if they are in contact (conduction). 7

Thermal Energy Transfer 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) CONVECTION: heat transferred by the circulation or movement of a liquid or gas. (fluids) 8

Thermal Energy Transfer: Convection A fluid is a liquid or gas and has the ability to flow. Solids, however, maintain their position 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 9

Thermal Energy Transfer: Convection 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 10

Thermal Energy Transfer: Convection When you look at the road in the summertime on a hot day, you may notice that the air above the road looks “blurry” – this is convection taking place as the hot air directly over the road absorbs the heat from the road and rises. Although the explanation can be quite complex, convection can help explain why mirages are seen in the desert. 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 11

Examples of convection where heat is transferred in fluids. Convection Ex. #1 Convection Ex. #2 Convection Ex. #3 Convection occurring in water inside a pot that is on a stove Convection occurring in a room with a radiator. Convection occurring in the atmosphere. 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 12

Convection Currents The upward movement of warm air and downward movement of cool air forms convection currents. Heated fluid (liquid or gas) expands, becoming less dense. Because it is less dense, it rises. Cooler fluids rushes in to replace the air that lifted up. As the warm fluid rises and cool fluid falls, a circular pattern is created known as a convection current Eventually the warmer air cools and begins to fall again. COLD HOT 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 13

6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 14

Thermal Energy Transfer If conduction deals with solids and convection deals with liquids and gases, how does heat arrive to Earth from the Sun? There is very little matter in the 93 million miles between the Sun and the Earth.

Thermal Energy Transfer Heat can travel in waves without a medium (a liquid, solid, or gas). These waves are called electromagnetic waves.

Electromagnetic Wave Spectrum

Thermal Energy Transfer: Radiation 6.P.3.1 Radiation is energy that travels across distances in the form of electromagnetic waves. The heat you feel from a fireplace, campfire or the sun travels directly to you as infrared radiation. This is part of the Electromagnetic Wave Spectrum. 18

Thermal Energy Transfer: Radiation 6.P.3.1 Radiation is energy that travels across distances in the form of electromagnetic waves. You can’t see infrared radiation, but you can feel it as heat. 19

The Electromagnetic Wave Spectrum The light we see with our eyes is really a very small portion of what is called the "Electromagnetic Spectrum." The Electromagnetic Spectrum includes all types of radiation - from the X-rays used at hospitals, to radio waves used for communication, and even the microwaves you cook food with.

Thermal Energy Transfer: Radiation 6.P.3.1 Radiation is energy that travels across distances in the form of electromagnetic waves. All of the forms of electromagnetic energy in the spectrum can travel through the universe as waves – we call this radiation. 21

Thermal Energy Transfer: Radiation RADIATION: heat transferred through matter or empty space (no direct contact) by electromagnetic waves. 6.P.3.1 Radiation is energy that travels across distances in the form of electromagnetic waves. 22

Energy in the Atmosphere Heat transfer by radiation Heat transfer by convection Heat transfer by convection Heat transfer by conduction 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) Heat energy is transferred by a number of ways. 23

6.P.3.1 Thermal energy is transferred through a material by the collisions of atoms within the material Heat flows through materials or across space from warm objects to cooler objects, until both objects are at equilibrium. Heat travels through solids, primarily by conduction. Heat is circulated in fluids, both liquids and gases, through the process of convection. Radiation is energy that travels across distances in the form of electromagnetic waves. Over time, thermal energy tends to spread out through a material and from one material to another if they are in contact (conduction). Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection 24

Conduction Video Clips http://www.youtube.com/watch?v=9joLYfayee8 http://www.youtube.com/watch?v=w_IbPRNZ6ho 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 25

Convection Video Clips Convection Current Video clip http://www.youtube.com/watch?v=7xWWowXtuvA&feature=related 6.P.3.1 Heat is circulated in fluids, both liquids and gases, through the process of convection. Thermal energy can also be transferred by means of currents in air, water, or other fluids (convection) 26

Radiation Video Clips Radiation Video clip http://www.youtube.com/watch?v=gY9BpJmhIrE

Shout it out!!

Conduction?? Convection?? Radiation?? a. heating a cup of water in a microwave oven b. seeing a lightning bolt convection conduction e. a burner coil getting hot on an electric stove c. electricity moving as a current convection d. heat moving within fluids radiation f. sun rays reaching earth convection i. air travels this way g. the heat you feel as you stand in front of a fireplace radiation h. the handle of a cold spoon heats up when dipped in a hot bowl of soup conduction radiation m. transfer of heat through space conduction l. frying a pancake on a griddle convection j. water in a pot boils radiation k. heat you feel as you hold your hand above a hot stove p. fast moving atomic particles colliding with slower moving particles conduction radiation o. heat moving as a wave conduction n. transfer of heat through solids

Review Rap Review of conduction, convection, and radiation rap video http://www.youtube.com/watch?v=7Y3mfAGVn1c

Which materials assist or limit thermal energy transfer? 6.P.3.3 There are some things that we use daily that we want to conduct heat easily. Most of these items are made of materials that conduct heat readily: aluminum, steel, copper. We call these materials thermal conductors. Similarly, there are things that we do not want to conduct heat (pot handles, spatula, cooking utensils) and these items are generally made of materials that limit heat transfer. We call such materials thermal insulators. Expansion joint strips in bridges allow for the bridge to expand in hot weather and not break. These same joint strips allow for the bridge to contract in cold weather and not break. Electrical energy also passes through conductors. An electrical conductor is a material through which an electrical current can flow easily. An electrical insulator is a material through which electrical current does not readily flow. Electrical conductors include most metals, while most nonmetallic solids (rubber, glass, porcelain, ceramic) are insulators. 31

What do you think causes pot holes in the road? Think about our last unit on Matter and our discussions of expansion…

Potholes form because asphalt road surfaces eventually crack under the heat of the day and the constant stresses of traffic. These cracks allow snow and rainwater to seep into the underlying dirt and gravel. During cold nights, the water freezes and expands, pushing out some of the dirt and gravel, leaving a hole when the water eventually melts. This whole process repeats itself over and over. Even in places where the air temperature rarely falls below freezing, excessive rainfall or flooding can eat away at the road.

THERMAL CONDUCTORS Some materials are good conductors of thermal energy – they let heat pass through them easily.

THERMAL CONDUCTORS METALS, such as aluminium, copper, and steel are good THERMAL CONDUCTORS ...because heat passes through them quickly – metal normally feels COLD 35

THERMAL CONDUCTORS Conductor – a material that transfers thermal or electrical energy very well. * Conductors allow energy (thermal and electrical) to easily flow through them

Some Materials Do Not let Heat pass through them THERMAL INSULATORS Some Materials Do Not let Heat pass through them Oven Mitt Wooden handle Wooden handle

THERMAL INSULATORS Wood, plastic, glass, wool and rubber are all insulators. *insulators are poor conductors of both thermal and electrical energy Wooden handle

THERMAL INSULATORS Insulator – a material that does not transfer thermal or electrical energy very well. Wooden handle

Insulators and Conductors both have important Uses Wires are coated in plastic – electricity cant flow through it so you don’t get a shock if you touch it Copper wire allows electricity to flow through

Insulators and Conductors both have important Uses A plug has metal pins – conduct electricity, and a plastic cover to hold with your hands

Thermal Expansion: an increase in the size of a substance in response to an increase in the temperature of the substance. background 43

Can energy transform (change)? 6.P.3.3 44

Energy Transforming The law of conservation of energy states that energy can neither be created nor destroyed. It can only be converted from one form to another. background 45

Energy Transforming

Energy Transforming Some thermal energy in all materials is transformed into light energy 6.P.3.3 47

Energy Transforming For example, a light bulb works by transforming electric energy into thermal energy. The thermal energy is then transformed into light energy. ELECTRIC ENERGY THERMAL ENERGY LIGHT ENERGY

Energy Transforming Light energy is radiated into the environment by electromagnetic waves. 6.P.3.3 49

Energy Transforming Once the electromagnetic waves strike another material they are transformed back into thermal energy. if you put your hand near a lit light bulb, you can FEEL the heat, without touching it