Thermal Energy Review

Thermal Energy Review

Middle School

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Learning Objectives

• Define thermal energy and explain how it is different from temperature.

• Describe the three ways heat moves: conduction, convection, and radiation.

• Explain how thermal energy moves and what thermal equilibrium is.

• Explain the difference between thermal conductors and thermal insulators.

Key Vocabulary

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Thermal Energy

The total kinetic energy of the moving particles of matter within an object.

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Temperature

A measure of the average kinetic energy of the atoms or molecules within a substance.

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Heat

Thermal energy that flows from something at a higher temperature to something at a lower one.

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Conduction

The transfer of thermal energy by collisions between particles in matter.

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Convection

The transfer of thermal energy in a fluid by the movement of warmer and cooler fluid.

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Radiation

The transfer of energy by electromagnetic waves, which can happen through gases or a vacuum.

What Are Heat and Temperature?

• All matter is made of particles that are constantly in motion.

• Temperature measures the average speed of these moving particles.

• Heat is the transfer of energy from warmer to cooler objects.

Multiple Choice

What is the key difference between thermal energy and temperature?

• They are the same concept and can be used interchangeably.

• Thermal energy is the total kinetic energy of all particles, while temperature is the average kinetic energy.

• Thermal energy measures heat, while temperature measures cold.

• Temperature is the total kinetic energy, while thermal energy is the average kinetic energy.

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Thermal Energy, Temperature, and Mass

• Temperature measures the average energy of particles, while thermal energy is the total energy.

• An object's mass is a key factor in its total thermal energy.

• A large bowl of soup has more thermal energy than a smaller mug.

• This is because the bowl contains more soup and therefore has more mass.

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Multiple Choice

An iceberg has a very low temperature but a very large mass. A cup of hot coffee has a high temperature but a small mass. Which statement is correct?

• They have the same amount of thermal energy.

• The temperature of the iceberg is higher than the coffee.

• The coffee has more thermal energy than the iceberg.

• The iceberg has more thermal energy than the coffee.

Methods of Heat Transfer

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Conduction

• ​Heat transfers through the direct contact and collision of particles.

• ​​This process occurs in solids, liquids, and also in various gases.

• ​A pan getting hot on a stove is an example.

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Convection

• ​Heat moves through the movement of fluids like liquids or gases.

• ​​Warmer fluid rises, and the cooler, denser fluid begins to sink.

• ​This movement creates a flow called a convection current.

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Radiation

• ​Energy is transferred through space by invisible electromagnetic waves.

• ​​This type of heat transfer does not require any matter.

• ​Feeling the warmth of the sun is a common example.

Multiple Choice

A bird is warming itself in the sun. This is an example of which type of heat transfer?

• Radiation

• Conduction

• Equilibrium

• Convection

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Conductors and Insulators

• Conductors are materials that let heat pass through them quickly and easily.

• Metals like copper and steel are great conductors used for pots.

• Insulators are materials that slow down the flow of heat energy.

• Plastic, wood, and air are insulators that help keep things cool.

Multiple Choice

Why is the handle of a metal cooking pot often made of a material like plastic or wood?

• Because those materials are good conductors of heat.

• To make the pot look more stylish.

• Because those materials are good insulators, slowing the transfer of heat to a person's hand.

• Because metal is a poor conductor of heat.

Thermal Equilibrium

• Heat energy always flows from a warmer object to a cooler one.

• Energy transfer continues until both objects reach the same temperature.

• When temperatures are equal, objects are in thermal equilibrium and heat flow stops.

Multiple Choice

When does the transfer of thermal energy between two objects that are touching each other stop?

• When both objects reach thermal equilibrium.

• The transfer of energy between objects never stops.

• When the colder object becomes hotter than the originally hot object.

• When one object runs out of thermal energy.

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Laws of Thermodynamics & Formulas

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Multiple Choice

Based on the fundamental principles of thermodynamics, which of the following events is possible?

• An ice cube gets colder when placed in a warm room.

• A glass of warm water placed in a cold room spontaneously begins to boil.

• Heat flows from the cool air in a room into a hot bowl of soup.

• A cup of hot chocolate slowly cools down as it sits on a table.

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Common Misconceptions About Heat

Misconception	Correction
Cold is a substance that flows into objects.	"Cold" is the absence of thermal energy. Objects feel cold as they lose heat.
Heat and temperature are the same thing.	Temperature is average energy of particles. Heat is the transfer of that energy.
A high temperature means more thermal energy.	A large, cold object can have more energy than a small, hot one.
Insulators completely stop the flow of heat.	Insulators only slow down the transfer of heat, not stop it entirely.

Multiple Choice

If you place a metal spoon and a wooden spoon in a cup of hot soup, why does the handle of the metal spoon get hot much faster?

• Because convection only happens in the metal spoon, not the wooden one.

• Because metal is a better thermal conductor, allowing heat to transfer quickly along it.

• Because metal is a better thermal insulator, trapping the heat.

• Because the metal spoon has a greater mass than the wooden spoon.

Multiple Choice

A large warehouse and a small walk-in closet are both heated to the same temperature of 70°F. How do their thermal energies compare?

• The closet has more thermal energy because the air is more compact.

• The large warehouse has more thermal energy because it contains a much greater mass of air particles.

• They have the same thermal energy because their temperatures are equal.

• It is impossible to compare their thermal energies without knowing the pressure.

Multiple Choice

You want to design a container that keeps food hot for as long as possible. What combination of materials and features would be most effective and why?

• A box made of dark plastic to absorb heat from the sun and keep the food warm.

• A container with a shiny metal interior and a foam-insulated outer layer to reduce heat loss from radiation and conduction.

• A container with a single thin wall to make it lightweight and easy to carry.

• A box made entirely of aluminum to conduct heat evenly around the food.

Multiple Choice

A block of ice at 0°C is dropped into a cup of warm soda. Describe what will happen to the motion of the soda molecules and the ice molecules over time.

• The motion of the molecules will not change, but the temperature of the soda will drop instantly.

• Both types of molecules will stop moving as soon as they come into contact.

• The fast-moving soda molecules will speed up, and the slow-moving ice molecules will slow down further.

• The soda molecules will slow down as they transfer energy to the ice molecules, causing the ice molecules to speed up (melt and warm up).

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Summary

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4