Temperature and Energy

Temperature and Energy

Middle School

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Learning Objectives

• Define thermal energy as the energy from the movement of tiny molecules.

• Explain how temperature relates to the speed and kinetic energy of molecules.

• Describe how energy moves from warmer objects to cooler ones until equilibrium.

• Identify how mass and material type affect changes in a substance's temperature.

Key Vocabulary

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Molecule

The smallest unit of a substance, which is in constant, random motion.

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Kinetic Energy

The energy an object has due to its motion. Faster molecules have more kinetic energy.

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Temperature

A measure of the average kinetic energy of the molecules in a substance.

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Thermal Energy

The total kinetic energy of all the molecules in a substance.

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Collision

When two or more molecules bump into each other, which can transfer energy.

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Energy Transfer

The movement of energy from a warmer object or region to a cooler one.

Key Vocabulary

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Equilibrium

A stable state where molecules in a system have the same average speed and temperature.

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System

A group of interacting parts that form a whole, like two objects in contact.

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Heat

The transfer of thermal energy between objects due to a temperature difference.

Molecules, Motion, and Temperature

• All things are made of moving molecules with kinetic energy.

• Hot things have fast-moving molecules and high temperatures.

• Cold things have slow-moving molecules and low temperatures.

Multiple Choice

What does the temperature of an object indicate?

• The speed of its moving molecules

• The total number of molecules it has

• The size of its individual molecules

• The color and brightness of the object

Multiple Choice

What is the main difference between the molecules in a cup of hot soup and a glass of cold water?

• The molecules in the soup are moving faster.

• The molecules in the water are larger.

• The soup has more molecules than the water.

• The water molecules have no kinetic energy.

Multiple Choice

Which statement best describes how molecular motion changes as temperature increases?

• Molecules move slower and closer together.

• Molecules stay the same distance apart but change shape.

• Molecules stop moving completely.

• Molecules move faster and farther apart.

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Temperature vs. Heat

Temperature

• It measures the average energy of motion of the molecules in a substance.

• Temperature tells us how hot or cold an object is, measured in degrees.

• It is a property that an object has, not something that can move.

Heat

• Heat is the energy that moves from a warmer object to a cooler one.

• It is the transfer of energy due to a difference in temperature between objects.

• For example, your warm hand transfers heat to a cold ice cube when you touch it.

Multiple Choice

What does temperature measure?

• The average energy of motion of the molecules in a substance

• The total energy transferred between two objects

• The amount of space an object takes up

• The force of gravity acting on an object

Multiple Choice

What is the key difference between heat and temperature?

• Heat is energy that moves, while temperature is a measurement of an object's energy.

• Temperature is a form of energy, while heat is a property of a single object.

• Heat and temperature are two different words for the same thing.

• Temperature measures how much heat an object can store.

Multiple Choice

If a warm metal spoon is placed into a cup of cold ice cream, what is the most likely outcome?

• Energy will move from the spoon to the ice cream.

• Energy will move from the ice cream to the spoon.

• The spoon will get colder, but no energy will move.

• Both the spoon and the ice cream will gain energy.

Energy Transfer Through Collisions

• Energy transfers when molecules from different temperature objects collide.

• Faster, warmer molecules lose energy to slower, cooler molecules.

• This repeated process transfers energy from hotter to colder areas.

Multiple Choice

What happens when molecules from warmer and cooler objects collide with each other?

• Energy is transferred from one molecule to the other.

• The molecules are destroyed by the impact.

• The molecules combine to form a new substance.

• Energy is created during the collision.

Multiple Choice

What is the relationship between a warmer, faster molecule and a cooler, slower molecule during a collision?

• Energy moves from the warmer molecule to the cooler molecule.

• Energy moves from the cooler molecule to the warmer molecule.

• Both molecules gain an equal amount of energy.

• Both molecules lose all of their energy.

Multiple Choice

If a hot object is placed in contact with a cold object, what is the most likely outcome after many molecular collisions occur?

• The hot object gets cooler and the cold object gets warmer.

• The cold object transfers its coldness to the hot object.

• Both objects become hotter as molecules collide.

• The temperature of both objects remains the same.

Reaching Equilibrium

• Energy transfer stops when a system reaches a stable state called equilibrium.

• At equilibrium, both objects have the same temperature and average molecule speed.

• Energy transfer is balanced, so the temperature does not change.

Multiple Choice

What happens to the transfer of energy when a system reaches equilibrium?

• The energy transfer stops.

• The energy transfer speeds up.

• The energy transfer reverses direction.

• The energy transfer becomes unbalanced.

Multiple Choice

Which statement best describes the conditions of a system at equilibrium?

• The objects have the same temperature and molecule speed.

• One object is hot and the other is cold.

• The molecules in one object move faster than the other.

• The temperature of the system is constantly changing.

Multiple Choice

If a warm metal spoon is placed into a cup of cold water, what is the most likely outcome?

• The spoon and the water will eventually reach the same temperature.

• The spoon will get warmer and the water will get colder.

• The water will get warmer, but the spoon's temperature will not change.

• The spoon will become cold, but the water will stay the same temperature.

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The Law of Conservation of Energy

• A fundamental rule in science is the law of conservation of energy.

• This law states energy is not created or destroyed, only transferred.

• When one object loses kinetic energy, another object must gain it.

• An air conditioner transfers thermal energy from inside a house to outside.

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Multiple Choice

What is the law of conservation of energy?

• Energy is not created or destroyed, only transferred.

• Energy can only be created by powerful machines.

• Energy is permanently lost when it is used.

• Some objects can create their own energy.

Multiple Choice

If one object loses energy, what must happen according to the law of conservation of energy?

• The energy disappears from the universe.

• The energy transforms into matter.

• Another object must gain the energy that was lost.

• The object that lost energy stops moving forever.

Multiple Choice

Which statement best explains how an air conditioner demonstrates the law of conservation of energy?

• It creates new cold energy to cool the house.

• It destroys the thermal energy that is inside the house.

• It moves thermal energy from inside the house to the outside.

• It uses up energy until there is none left.

Factors Affecting Temperature Change

• Energy transfer is needed to change an object's temperature.

• Larger objects need more energy to change their temperature.

• Different materials require different amounts of energy to change temperature.

Multiple Choice

What is needed to cause a change in an object's temperature?

• A transfer of energy is required.

• The object must be in motion.

• The object must change its shape.

• A chemical reaction must occur.

Multiple Choice

What is the relationship between an object's size and the energy required to change its temperature?

• A larger object needs more energy to change its temperature.

• A larger object needs less energy to change its temperature.

• An object's size does not affect the energy needed.

• Only very large objects can change temperature.

Multiple Choice

If two blocks of the same size are heated with the same amount of energy, but one's temperature increases more than the other, what is the best explanation?

• The block that heats up faster is made of a different material.

• The two blocks must have different sizes.

• One block received more energy than the other.

• The blocks are different colors.

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Common Misconceptions

Misconception	Correction
Cold is a substance that moves between objects.	Cold is the absence of thermal energy. Heat is what actually moves.
Temperature and heat are the same thing.	Temperature measures molecule energy. Heat is the transfer of that energy.
Objects that feel cold don't have any heat.	All objects have heat. Some objects just transfer heat away from you faster.

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Summary

• Temperature measures the average kinetic energy of molecules.

• Heat is energy that transfers from warmer to cooler objects through molecular collisions.

• Energy flows until a stable state of equilibrium is reached.

• Energy is conserved and the amount needed for temperature change depends on mass.

Poll

On a scale of 1-4, how confident are you about explaining thermal energy concepts to a friend?

• 1 - Not confident at all

• 2 - A little confident

• 3 - Mostly confident

• 4 - Very confident!