# By Marvin Lowe. Teacher's Notes Subject: Physics (Heat Energy) Topic: Conservation of energy- Heat transfer Grades: 8 Prior Knowledge: 1) phases of matter-

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By Marvin Lowe

Teacher's Notes Subject: Physics (Heat Energy) Topic: Conservation of energy- Heat transfer Grades: 8 Prior Knowledge: 1) phases of matter- solid, liquid, gas, plasma 2) phase changes- solid to liquid, liquid to gas, solid to gas, liquid to solid, gas to liquid 3) molecules, elements, metals, nonmetal 4) density- molecule spacing of solid liquid and gas 5) buoyancy

Lesson Objectives By the end of this lesson student’s should be able to explain how heat and temperature are due to molecular motion and how energy is transferred define and explain the three types of heat transfer compare conductors and insulators

Lesson Notes Motion can produce heat. The amount of heat produced depends on the amount of motion. A molecule at any temperature is the same size. M atter is made of atoms and molecules, which are always in motion. The speed of the molecules depends on how much energy they have, which affects the state of matter they are in – solid, liquid, gas or plasma. The less energy the particles have the less they move and the more solid and colder the matter is. The more energy the particles have the more they move so the more liquid or gaseous and hotter the matter is. H eat is a form of energy caused by the friction between molecules due to the internal motions of molecules. Heat transfer is heat energy moving from a warmer object to a cooler object. T here are three types of heat transfer: 1) Conduction is heat transferred by the direct contact of molecules. 2) Convection is heat transferred through a liquid or gas by means of up-and-down movements called convection currents. 3) Radiation is heat transferred through empty space by invisible infrared rays.

Where does heat come from? Touch each image and discuss. Motion causes friction which produces heat. The amount of heat produced depends on the amount of motion and friction.

How can motion create heat? Touch each image to view the different energy levels of the molecule. Water is made of molecules. Molecules are always in motion. The more molecular motion and friction the more heat. The energy level of the molecules determines their state of matter.

What is heat? Touch each image to see how the water molecules react. Heat is a form of energy caused by the internal motion of molecules and friction as the molecules rub against each other. The hotter a substance is, the faster the molecules are moving.

What is heat transfer? Drag the hand over the ice or pan, observe the heat transfer for each. Heat transfer is when heat energy moves from a warmer object to a cooler object.

heat transferred through empty space by invisible infrared rays. heat transferred through a liquid or gas by means of up-and-down caused by differences in temperature and density. heat transferred by the direct contact of molecules. What are the three type of heat transfer? Drag the terms to the correct definitions. Conduction Convection Radiation

Correct Answer heat transferred through empty space by invisible infrared rays. heat transferred through a liquid or gas by means of up-and-down. heat transferred by the direct contact of molecules. Conduction Convection Radiation

Conduction Touch the image. Conduction is the transfer of energy through matter by direct contact of particles.

Do some substances conduct heat more rapidly than others? Write your answers and touch the clouds to reveal some examples. Can you think of objects that are used to conduct heat or energy? Copper wire conducts energy. Metal pots and pans conduct heat to cook food.

Do some substances conduct heat and energy poorly? Write your answers and touch the clouds to reveal some examples. Can you think of objects that are used to stop the conduction of heat or energy? A winter coat stops energy from being conducted out of a body. A hot pad stops conduction from a hot pan to the hand. Insulators are substances that do not conduct heat and energy well. Cloth, wood, glass, plastic, and rubber conduct energy and heat very slowly when in contact with vigorously moving particles of a hot object.

Conduction Lab Drag the objects to connect the battery to the light bulb. Find out which items conduct energy.

Convection Click on the red molecule to view the 4 stages of convection. Convection is heat that is transferred in liquids or gases by means of up and down movements of matter. The hot molecules move up and the cold molecules move down. Cycles are created called convection currents.

Radiation Touch each image to see examples of heat radiation. Radiation is the heat energy that is transferred through empty space by invisible infrared radiation.

Review Question Drag the correct answer to match definition. 1) Energy caused by motion of particles in matter. 2) Tiny particles that make up matter. Heat Transfer Molecules Heat Answer Options Heat Molecules Heat Transfer 3) Movement of heat from a warmer to a cooler object.

Review Question Drag the correct answer to match definition. 1) Movement of heat by direct contact. 2 ) Movement of heat that is transferred through empty space. 3) Movement of heat in an up and down motion of particles that occurs in liquids and gases. Convection Radiation Conduction Answer Options Radiation Conduction Convection

Review Question Drag the correct answer to match the example. 3) Radiation 2) Conduction 1) Convection 1) Bacon cooking in a pan. 2) Air above a grassland plain warming up in the sun causing violent updrafts that lead to the formation of a tornado. 3) The warmth of a fireplace heating a person in a room. Answer Options Conduction Radiation Convection

1 A They are good conductors of heat. B They are poor conductors of heat. Why should the handle of a pot be made of wood or plastic rather than metal?

2 What happens to molecules as they heat up? B They move less vigorously. C They move more vigorously. D No change occurs. AThey burn up and stop moving.

3 Which is moving faster- particles in a gas or a solid? A gas B solid

4 What happens to molecules as they begin to cool? A They freeze and stop moving. B They move less vigorously. C They move more vigorously. D No change occurs.

5 Cold air is more dense than hot air? A True B False

6 A rises, heats up, sinks, cools B sinks, cools, rises, heat ups C heats up, cools, rises, sinks D heats up, rises, cools down, sinks What is the correct order of a convection current?

7 A convection B conduction C radiation In which type of heat transfer do particles actually move around?

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