WalkIn Take out notebook folder pencil box Copy

Walk-In • Take out notebook, folder, pencil box. • Copy the question and answer in sentences: • Why does a cup of hot chocolate get cold when left in a room for some time?

Answer • The heat in the hot chocolate gets transferred to the air around it.

Three Kinds of Heat Transfers • Today, we will explore three kinds of heat transfers… • Copy down notes that are written in PURPLE!

Conduction, Convection, and Radiation

Heat Energy • Energy is what makes it possible for things to move and for processes to happen. • All materials are made of tiny molecules that are always moving, and giving off heat from moving. . • The amount of heat depends on how fast the molecules move. Faster = more heat! • As the molecules move faster, they take up more space and make the object expand.

Let’s model this! • Stand up and put your hands out in front of you. • When told to start, move in RANDOM DIRECTIONS. • If you bump into someone, pat their hands LIGHTLY. • How is heat being generated?

Heat Transfer • Heat can be transferred from one object to another in 3 different ways: – Conduction – Convection – Radiation

How Heat Is Transferred

Why do people wrap their hands around a cup of coffee?

Conduction • Conduction refers to heat transfer from one SOLID to another SOLID. • As molecules heat up they move faster and expand. • When you touch one hot surface to another, the hot molecules bump into the other molecules which makes them start to move faster. • An object gets hotter from the movement of the molecules. • All solid objects conduct heat. • Some are better conductors than others. • Metals are good conductors of heat.

Examples of Conduction Discuss three examples…

Convection • Convection refers to heat traveling through liquids or gases, like water or air. • As molecules heat up, the heat makes the molecules move more rapidly and expand. • This creates currents in liquids or gases – hot air rises and cold air sinks. • Scientists use global and local wind patterns to predict weather.

Examples of Convection Discuss 3 examples

Radiation • Radiation refers to the release of invisible heat energy waves from the sun or fire. • There is no movement of molecules to transfer heat. • You can feel warmth without touching the source because the heat radiates. • Heaters and radiators get their name from this type of heat. • When the radiant energy from the sun hits the earth, the earth soaks up the energy and changes it into heat.

Examples of Radiation Discuss 2 examples

Balance of Heat • If a hot object is near a cold object, the hot object will transfer heat to the cold object until they reach a state of balance. • Balance happens when the temperatures of both objects are the same.

Thermal Equilibrium • The scientific words for balance of heat is thermal equilibrium.

REVIEW - Methods of Heat Transfer Conduction • Heat traveling through solids. • Two objects must touch Convection • Heat traveling through liquids or gases Radiation Release of invisible heat energy waves from the sun or fire. No movement of molecules

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