Energy and Matter

Energy and Matter

Middle School

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Learning Objectives

• Define kinetic energy and its link to temperature and states of matter.

• Describe the three ways thermal energy transfers: conduction, convection, and radiation.

• Analyze how mass and material type affect the transfer of thermal energy.

• Apply scientific ideas to design a device that controls thermal energy transfer.

Key Vocabulary

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Kinetic Energy

This is the energy of motion in the particles of matter that make up a substance.

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Potential Energy

This is the stored energy resulting from the forces and interactions between particles in a substance.

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Temperature

Temperature is a measure of the average kinetic energy of the particles within a specific substance.

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Thermal Energy

This is the total kinetic and potential energy of all the particles within a given system.

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Conduction

This type of heat transfer occurs when particles of matter are in direct contact and collide.

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Convection

This type of heat transfer occurs through the movement of particles within a fluid, such as a liquid or a gas.

Key Vocabulary

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Radiation

Radiation is the transfer of heat through space by electromagnetic waves without any direct contact.

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Specific Heat

Specific heat is the energy needed to raise one kilogram of a substance by 1^oC.

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Thermal Conductor

A thermal conductor is a material that allows thermal energy, or heat, to pass through it easily.

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Thermal Insulator

A thermal insulator is a material that resists or slows the transfer of thermal energy or heat.

Particles, Motion, and Kinetic Energy

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Solids

• Particles in a solid are packed very closely together.

• They are held in fixed positions, vibrating constantly.

• Solids have the lowest amount of kinetic energy.

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Liquids

• Particles in a liquid are close but can move.

• They easily slide past one another, allowing flow.

• Liquids have more kinetic energy than solids.

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Gases

• Gas particles are very far apart from each other.

• They move quickly and randomly in all available space.

• Gases have the highest amount of kinetic energy.

Multiple Choice

Which state of matter consists of particles that are tightly packed and vibrate in fixed positions?

• Solid

• Liquid

• Gas

• Energy

Multiple Choice

What is a key difference between the particles in a liquid and the particles in a gas?

• Liquid particles are close together, while gas particles are far apart.

• Liquid particles have more energy than gas particles.

• Liquid particles are in fixed positions, while gas particles can flow.

• Liquid particles move randomly, while gas particles vibrate.

Multiple Choice

A substance is heated, causing its particles to gain a large amount of kinetic energy. The particles begin to move quickly and spread far apart. What conclusion can be drawn?

• The substance has changed from a liquid to a gas.

• The substance has changed from a solid to a liquid.

• The substance has become a denser solid.

• The substance's particles have lost kinetic energy.

Temperature and Thermal Expansion

• Temperature measures how fast particles in a substance move.

• When heated, particles move faster and farther apart, causing expansion.

• When cooled, particles slow down and move closer, causing contraction.

Multiple Choice

What does temperature measure?

• How fast particles in a substance move.

• How large the particles in a substance are.

• How much a substance weighs.

• How many particles are in a substance.

Multiple Choice

What happens to the particles of a substance when it is heated?

• The particles move faster and farther apart, causing the substance to expand.

• The particles slow down and move closer together, causing the substance to contract.

• The particles stop moving completely.

• The particles change in size but not in speed.

Multiple Choice

On a very hot summer day, a concrete sidewalk is pushed up and cracks. What is the best explanation for why this happens?

• The sidewalk sections expanded on a hot day and pushed against each other.

• The sidewalk sections contracted on a hot day and pulled apart.

• The sun melted the concrete, causing it to buckle.

• Heavy cars must have cracked the sidewalk.

States of Matter & Phase Changes

• Particles are arranged differently in solids, liquids, and gases.

• Matter changes between states through melting, freezing, and vaporization.

• During a phase change, the temperature of the substance stays the same.

Multiple Choice

What is the main difference between solids, liquids, and gases?

• The way their particles are arranged

• The color of their particles

• The size of their individual particles

• The shape of their individual particles

Multiple Choice

What is the scientific term for the process of a substance changing from a solid to a liquid or a liquid to a gas?

• A phase change

• A chemical reaction

• A temperature reversal

• A new substance

Multiple Choice

If a block of ice is melting in a warm room, what will happen to its temperature during the melting process?

• The temperature of the ice will start to increase immediately.

• The temperature of the ice will stay the same until it has all melted.

• The temperature of the ice will decrease as it melts.

• The temperature of the ice will fluctuate up and down while melting.

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Energy in Phase Changes: Kinetic vs. Potential

• Kinetic energy is related to particle speed and changes a substance's temperature.

• Potential energy is stored energy based on the distance between particles.

• During a phase change, energy increases potential energy, not the temperature.

• Heating curves show this: slopes are kinetic gain, plateaus are potential gain.

Multiple Choice

What is the primary difference between kinetic energy and potential energy in the particles of a substance?

• Kinetic energy is the energy of moving particles, while potential energy is the stored energy based on the distance between particles.

• Kinetic energy is only found in hot substances, while potential energy is only found in cold substances.

• Kinetic energy is measured by a thermometer, while potential energy is measured by a scale.

• Kinetic energy is used during a phase change, while potential energy is used to increase temperature.

Multiple Choice

When a substance is being heated but is not undergoing a phase change, what is the relationship between the energy, particle motion, and temperature?

• The kinetic energy of the particles increases, causing the temperature to rise.

• The potential energy of the particles decreases, causing the temperature to drop.

• The distance between particles increases, but the temperature stays the same.

• The particles stop moving completely, and the temperature becomes zero.

Multiple Choice

A heating curve shows how a substance's temperature changes as energy is added. If a section of the curve is a flat, horizontal line (a plateau), what must be happening?

• Potential energy is increasing as the substance melts, but its temperature is not changing.

• Kinetic energy is increasing, causing the substance to get hotter.

• Both kinetic and potential energy are increasing at the same time.

• The substance is losing all of its energy to the environment.

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Energy Transfer: Conduction and Radiation

Conduction

• This is the transfer of thermal energy between substances that are in direct physical contact.

• Particles of a hotter substance collide with particles of a colder substance, transferring kinetic energy.

• An example is a metal spoon becoming hot after being placed in a cup of hot cocoa.

Radiation

• This is the transfer of thermal energy through space by electromagnetic waves.

• Unlike conduction, this process does not require any matter for the heat to travel through.

• An example is feeling the warmth of a campfire on your face without touching the fire.

Multiple Choice

What is conduction?

• The transfer of heat between substances in direct physical contact.

• The transfer of heat through empty space.

• The transfer of heat using electromagnetic waves.

• The transfer of heat through the movement of fluids.

Multiple Choice

What is the key difference between heat transfer by conduction and by radiation?

• Conduction requires direct contact between substances, while radiation does not.

• Radiation is the transfer of energy through particle collisions, while conduction is not.

• Conduction can travel through empty space, while radiation requires matter.

• Radiation only occurs in hot objects, while conduction only occurs in cold objects.

Multiple Choice

A person sits by a campfire while stirring a pot of hot soup with a metal spoon. Why does the person's face feel warm at the same time the spoon's handle gets hot?

• The person's face is warmed by radiation from the fire, while the spoon is heated by conduction from the soup.

• The person's face is warmed by conduction from the air, while the spoon is heated by radiation from the pot.

• Both the face and the spoon are heated primarily through conduction.

• Both the face and the spoon are heated primarily through radiation.

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What is Convection?

• Convection is heat transfer by the movement of particles in fluids like liquids or gases.

• When a fluid is heated, it expands, becomes less dense, and rises.

• Cooler, denser fluid then sinks to take the place of the warmer fluid.

• This circular motion creates convection currents that circulate and distribute thermal energy.

Multiple Choice

Which of the following best defines convection?

• Heat transfer through the movement of particles in fluids.

• Heat transfer through direct contact between solid objects.

• Heat transfer through electromagnetic waves.

• Heat transfer that only happens in a vacuum.

Multiple Choice

What causes the movement of fluid that creates a convection current?

• Heated fluid becomes less dense and rises, while cooler, denser fluid sinks.

• Heated fluid becomes denser and sinks, while cooler, less dense fluid rises.

• The fluid's particles stop moving and settle at the bottom.

• The fluid's particles all move in the same direction at the same speed.

Multiple Choice

If you were to heat a pot of water from the top surface instead of the bottom, what would most likely happen?

• The warm water will stay at the top, and the cooler water will remain at the bottom.

• The warm water will immediately sink to the bottom and push the cool water up.

• The water will circulate much faster than if it were heated from the bottom.

• The entire pot of water will heat up evenly all at once.

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Material and Specific Heat

Thermal Conductors

• Thermal conductors are materials that transfer thermal energy easily, like the metal in a cooking pan.

• They have a low specific heat, meaning they require less energy to increase in temperature.

• This property allows conductors to heat up very quickly when placed on a source of heat.

Thermal Insulators

• Thermal insulators are materials that do not transfer thermal energy well, like a plastic pot handle.

• They have a high specific heat, meaning they need more energy to increase their temperature.

• This property keeps them from getting hot quickly, which helps to protect you from burns.

Multiple Choice

What does it mean for a material to have a low specific heat?

• It requires less energy to increase its temperature.

• It requires more energy to increase its temperature.

• It is a material that does not transfer thermal energy well.

• It is a material that cools down very slowly.

Multiple Choice

What is the relationship between a material's specific heat and its use as a handle on a cooking pot?

• They have a low specific heat and heat up very quickly.

• They have a high specific heat and do not heat up quickly.

• They are thermal conductors that transfer heat easily.

• They are designed to match the color of the cooking pan.

Multiple Choice

If you wanted to design a cup that keeps a cold drink from getting warm too quickly on a hot day, what kind of material would be best to use and why?

• A material with a low specific heat, because it will heat up the drink.

• A material with a high specific heat, because it will resist temperature change.

• A thermal conductor, because it will transfer heat away from the drink.

• A shiny metal, because it will reflect the cold back into the drink.

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Factors Affecting Energy Transfer

Mass

• For the same energy input, a substance with more mass will show a smaller temperature change.

• This means it takes much more energy to heat up a larger or more massive object.

• For instance, a large pot of water takes longer to boil than a small cup of water.

Surface Properties

• A larger surface area allows for a quicker rate of energy transfer between two objects.

• Dark, matte surfaces are better at absorbing energy, which causes them to become warmer.

• Light, shiny surfaces are better at reflecting energy, which helps them to stay cooler.

Multiple Choice

If the same amount of energy is added to two objects, what will happen to the object with more mass?

• It will show a smaller temperature change.

• It will show a larger temperature change.

• Its temperature change will be unpredictable.

• Its temperature will not change at all.

Multiple Choice

What is the best explanation for why a black t-shirt feels warmer in the sun than a white t-shirt?

• Dark, matte surfaces are better at absorbing energy.

• Light, shiny surfaces are better at absorbing energy.

• Dark, matte surfaces have a smaller surface area.

• Light, shiny surfaces have more mass.

Multiple Choice

If four different pots of water are left in the sun for an hour, which one will experience the greatest temperature increase?

• A small, dark-colored pot of water.

• A large, dark-colored pot of water.

• A small, light-colored pot of water.

• A large, light-colored pot of water.

Planning a Thermal Energy Investigation

• Investigations explore how heat affects different masses and materials.

• We change one variable and measure the effect on another.

• Controls are factors we keep the same for a fair test.

Multiple Choice

In a scientific investigation, what is the purpose of a control?

• To make the investigation go faster.

• To change as many things as possible at once.

• To make sure the test is fair and the results are reliable.

• To get a different result every time.

Multiple Choice

What is the relationship between the variable that is changed and the variable that is measured in an investigation?

• To see how the variable being changed affects the variable being measured.

• To prove that the controlled variables have the biggest effect.

• To make sure that every variable is constantly changing.

• To show that the investigation has no clear purpose.

Multiple Choice

A scientist wants to investigate how the mass of a substance affects the amount of thermal energy it can absorb. Which experimental design would be the most effective and fair?

• Use different masses of the same material but apply the same amount of heat to each.

• Use the same mass of material but apply different amounts of heat to each.

• Use different materials with different masses and apply different amounts of heat.

• Use the same mass of different materials and apply different amounts of heat.

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Designing to Control Heat Transfer

Minimizing Heat

• Devices like a thermos are designed to minimize the transfer of thermal energy.

• A design criterion could be keeping water below 10°C for at least three hours.

• This is achieved using insulating materials like plastic, foam, and other reflective surfaces.

Maximizing Heat

• Devices like a cooking pan are designed to maximize the transfer of thermal energy.

• A key design criterion for a cooking pan is to transfer heat very quickly.

• This is achieved using conductive materials like metals such as copper or aluminum.

Multiple Choice

What is the primary purpose of using materials like plastic or metal when designing objects like thermoses and cooking pans?

• To control the transfer of thermal energy.

• To make the objects more durable and strong.

• To change the temperature of the objects.

• To make the objects less expensive to produce.

Multiple Choice

Why is a cooking pan typically made of metal, while a thermos uses materials like plastic and foam?

• Metal is conductive to maximize heat transfer, while plastic and foam are insulators to minimize it.

• Metal is more resistant to heat, while plastic and foam are not.

• Metal is used for cooking, while plastic and foam are used for storing liquids.

• Metal heats up slowly to cook food evenly, while plastic and foam cool down quickly.

Multiple Choice

An engineer is developing a new lunchbox intended to keep food cold for many hours. Based on the principles of thermal design, which feature would be most effective to include?

• An inner lining made of foam and reflective surfaces.

• A handle made of copper or aluminum.

• A thin shell made of a conductive metal.

• A dark-colored exterior to absorb heat.

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Energy Transfer and Changes in Kinetic Energy

• When an object’s kinetic energy changes, energy is transferred to or from it.

• ​For example, a braking car’s motion energy decreases as it slows down.

• The lost kinetic energy becomes thermal energy in the hot brakes and tires.

• We can also hear sound energy, which is part of the energy transfer.

Multiple Choice

What does it mean if an object's kinetic energy changes?

• That energy has been transferred

• That the object's mass has changed

• That new energy has been created

• That the object's energy has been destroyed

Multiple Choice

When a moving car uses its brakes, what is the relationship between its kinetic energy and the thermal energy in the brakes and tires?

• The car's kinetic energy is converted into thermal energy.

• The car's thermal energy is converted into kinetic energy.

• The brakes create new energy to stop the car.

• The kinetic energy is stored in the tires for later use.

Multiple Choice

A student hammers a nail into a board and notices that the nail head feels warm. Based on the principles of energy transfer, what is the best explanation for this?

• The kinetic energy from the moving hammer was converted into thermal energy in the nail.

• The nail gets hotter because it is made of metal.

• The wood transferred its own heat into the nail.

• The force of the hammer creates new heat energy in the nail.

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Common Misconceptions

Misconception	Correction
‘Cold’ moves from one object to another.	Thermal energy (heat) always moves from a warmer object to a cooler one.
Objects at rest, like a table, have no energy.	The particles in all objects are always moving, so they have kinetic energy.
Temperature and heat are the same thing.	Temperature is the average energy of particles. Heat is the transfer of that energy.
Energy can be lost or can disappear.	Energy is conserved. It only changes from one form to another.

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Summary

• Matter is made of particles; temperature measures their kinetic energy.

• Energy transfers from hotter to cooler objects via conduction, convection, and radiation.

• The amount of energy transfer depends on an object's mass and material.

• We can investigate and design devices that control heat transfer.

Poll

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

• 1

• 2

• 3

• 4