Particles in Motion

Particles in Motion

Middle School

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Learning Objectives

• Model and describe the motion of particles in solids, liquids, and gases.

• Explain the relationship between thermal energy, particle motion, and temperature.

• Predict how adding or removing thermal energy affects a substance's state.

• Explain how mass and the type of matter affect a substance's thermal energy.

• Define pressure in gases as a result of particle collisions with their container.

Key Vocabulary

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Particle

A particle is a very small piece or unit of matter, like an atom or a molecule.

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Kinetic Energy

Kinetic energy is the specific type of energy that an object possesses because of its motion.

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Temperature

Temperature measures the average kinetic energy of the particles within a substance, indicating its hotness or coldness.

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Thermal Energy

Thermal energy represents the total internal kinetic energy of all particles that make up an object.

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State of Matter

A state of matter is the distinct physical form that matter can exist in, like solid, liquid, or gas.

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Heat

Heat is the transfer of thermal energy from a hotter object or system to a colder one.

Key Vocabulary

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Pressure

The force exerted by particles when they collide with the surfaces of an object.

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Diffusion

The natural movement of particles from an area of high concentration to low concentration.

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Thermal Expansion

The tendency of matter to increase in volume when it is heated by energy.

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Thermal Contraction

The tendency of matter to decrease in volume when it is cooled down.

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Absolute Zero

The lowest possible temperature where all particle motion completely ceases to exist.

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Molecule

A group of two or more atoms that are chemically bonded together to form a substance.

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Particle Motion and Diffusion

• All matter is made of tiny particles in constant, random motion.

• These particles are always moving and colliding with each other.

• Diffusion is particles spreading from a crowded to a less crowded area.

• This process continues until the particles are spread out evenly.

Multiple Choice

What is diffusion?

• The process where particles spread out from a crowded area.

• The process where particles clump together in a small space.

• The process where particles stop moving completely.

• The process where particles become larger in size.

Multiple Choice

What causes particles to spread out during diffusion?

• The random movement and collision of particles.

• The force of gravity pulling particles down.

• The particles getting colder and slowing down.

• The container getting smaller and squeezing the particles.

Multiple Choice

If a drop of ink is placed in one corner of a container of water, what is the most likely outcome after a long period of time?

• The particles will spread out until they are evenly mixed throughout the container.

• The particles will remain in a single, concentrated drop.

• The particles will all move to one side of the container.

• The particles will stop moving as soon as they are added.

Particle Behavior in States of Matter

• In solids, atoms are closely spaced and vibrate in fixed positions.

• In liquids, molecules are in contact but can slide past one another.

• In gases, molecules are widely spaced and move rapidly and randomly.

Multiple Choice

How are the particles in a gas described?

• Widely spaced and moving rapidly

• Closely spaced and vibrating in fixed positions

• In contact with each other and sliding past one another

• Tightly packed together and not moving at all

Multiple Choice

What is the main difference between the movement of particles in a solid and a liquid?

• Particles in a solid are widely spaced, while particles in a liquid are close together.

• Particles in a solid move rapidly, while particles in a liquid move slowly.

• Particles in a solid vibrate in place, while particles in a liquid can slide past one another.

• Particles in a solid can slide past one another, while particles in a liquid vibrate in place.

Multiple Choice

Imagine you could see the individual molecules in a glass of water (a liquid). What would you expect to see if the water evaporated into a gas?

• The molecules would lock into fixed positions and only vibrate.

• The molecules would get closer together and slow down.

• The molecules would spread far apart and move much more rapidly.

• The molecules would stop moving completely and stay in one place.

Kinetic Energy and Temperature

• Kinetic energy is the energy of motion in particles.

• The faster a particle moves, the more kinetic energy it has.

• More motion lines in diagrams show faster particle movement.

Multiple Choice

What is kinetic energy?

• The energy stored in particles

• The energy of motion in particles

• The energy from a particle's size

• The energy that holds particles together

Multiple Choice

What happens to a particle's kinetic energy as it starts to move faster?

• The particle's kinetic energy decreases.

• The particle's kinetic energy increases.

• The particle's kinetic energy stays the same.

• The particle loses all of its energy.

Multiple Choice

A diagram shows two substances. The particles in Diagram A are drawn with many long motion lines, while the particles in Diagram B have very few, short motion lines. What conclusion can be drawn?

• The particles in Diagram A have more kinetic energy.

• The particles in Diagram B have more kinetic energy.

• The particles in both diagrams have equal kinetic energy.

• The diagrams do not show any information about kinetic energy.

Total Thermal Energy vs. Temperature

• Temperature measures the average kinetic energy of particles.

• Total thermal energy depends on temperature, mass, and state.

• More mass can mean more thermal energy, even at lower temperatures.

Multiple Choice

What does temperature directly measure?

• The average kinetic energy of particles in a substance.

• The total mass of a substance.

• The total energy of all particles in a substance.

• The state of matter of a substance.

Multiple Choice

Which factors are all used to determine a substance's total thermal energy?

• Temperature and average kinetic energy.

• Mass and volume.

• Temperature, mass, and state.

• Average kinetic energy and state.

Multiple Choice

Consider a small cup of hot tea and a large swimming pool of cool water. Which one likely has more total thermal energy and why?

• The cup of hot tea, because it has a higher temperature.

• The swimming pool, because it has a much larger mass.

• They both have the same amount of thermal energy.

• It is impossible to tell without knowing the exact temperatures.

Heat as Energy Transfer

• In science, heat and thermal energy have different meanings.

• Thermal energy is the total energy of moving atoms and molecules.

• Heat is the transfer of this energy from a warmer to a cooler object.

Multiple Choice

What is the scientific definition of heat?

• The transfer of energy from a warmer object to a cooler one.

• The total energy of moving atoms and molecules in an object.

• The energy an object has because of its position.

• The energy created when an object gets colder.

Multiple Choice

What is the relationship between thermal energy and heat?

• Thermal energy is the total energy of moving particles, while heat is the transfer of that energy.

• Heat is the total energy of moving particles, while thermal energy is the transfer of that energy.

• There is no difference; heat and thermal energy are the same thing.

• Thermal energy is only found in hot objects, while heat can be in any object.

Multiple Choice

If a cold metal spoon is placed into a cup of hot chocolate, what will happen to the energy?

• Energy will be transferred from the hot chocolate to the cold spoon.

• Energy will be transferred from the cold spoon to the hot chocolate.

• The spoon will get colder because the hot chocolate absorbs its energy.

• No energy will be transferred between the spoon and the hot chocolate.

Changes of State

• Adding or removing thermal energy changes a substance's state.

• Adding thermal energy can cause melting or evaporation.

• Removing thermal energy can cause condensation or freezing.

Multiple Choice

What is the primary factor that causes a substance to change its state?

• The addition or removal of thermal energy

• A change in the substance's mass

• The substance's initial temperature

• The pressure of the environment

Multiple Choice

What two processes are caused by a substance absorbing thermal energy?

• Melting and evaporation

• Condensation and freezing

• Melting and condensation

• Evaporation and freezing

Multiple Choice

Which scenario provides the best example of a change of state caused by the removal of thermal energy?

• Water vapor in the air forming ice crystals on a cold window.

• An ice cube turning into a puddle of water on the counter.

• A puddle on the sidewalk disappearing on a sunny day.

• A solid candy bar turning into a liquid in a hot car.

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Thermal Expansion and Contraction

• Heating a material makes its particles gain energy and move much faster.

• The fast-moving particles spread out, causing the material to expand or grow.

• Cooling a material causes its particles to lose energy and slow down.

• The slow-moving particles get closer, causing the material to contract or shrink.

Multiple Choice

What happens to a material when it is heated?

• Its total volume increases.

• Its total volume decreases.

• Its particles get heavier.

• Its particles stop moving.

Multiple Choice

Why does heating a material cause its volume to increase?

• The particles gain kinetic energy and move farther apart.

• The particles lose kinetic energy and come closer together.

• The particles become larger in size.

• The particles become chemically bonded.

Multiple Choice

If a liquid in a thermometer is moved from a warm room into a cold freezer, what is the best explanation for what will happen to the volume of the liquid?

• The liquid's volume will decrease because its particles will slow down and move closer together.

• The liquid's volume will increase because the cold will push the particles apart.

• The liquid's volume will stay the same because no liquid was added or removed.

• The liquid will turn into a solid instantly, keeping the same volume.

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Gas Pressure

• Gas pressure is the force from gas particles hitting container walls.

• Adding thermal energy makes gas particles gain kinetic energy and move faster.

• These faster particles collide more frequently and forcefully with the container walls.

• Increasing the temperature of a gas increases its overall pressure.

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Multiple Choice

What is gas pressure?

• The force created by gas particles hitting the walls of a container.

• The energy that gas particles lose when they get cold.

• The attraction that pulls gas particles toward each other.

• The space that a gas takes up inside a container.

Multiple Choice

What is the direct effect of adding thermal energy to gas particles?

• They lose kinetic energy and move slower.

• They gain kinetic energy and move faster.

• They stick to the walls of the container.

• They become larger in size.

Multiple Choice

If a sealed balloon is left in a hot car, what is the best explanation for what will happen to the gas pressure inside?

• The pressure will increase because the particles will hit the walls more frequently and forcefully.

• The pressure will decrease because the particles will try to escape the heat.

• The pressure will stay the same because the amount of gas has not changed.

• The pressure will drop to zero as the particles stop moving.

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Common Misconceptions

Misconception	Correction
Cold can be transferred from one object to another.	Heat transfers from your hand to a cooler object, making it feel cold.
Temperature measures the total energy in a substance.	Temperature measures the average kinetic energy of particles, not the total thermal energy.
Particles in a solid do not move at all.	The particles that make up solids are always vibrating in fixed positions.

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Summary

• All matter is composed of tiny particles that are in constant motion.

• Temperature measures the average kinetic energy of particles in a substance.

• Heat is thermal energy that transfers from a warmer to a cooler substance.

• Adding thermal energy can change a substance's state or cause it to expand.

Poll

On a scale of 1-4, how confident are you about explaining the relationship between particle motion and temperature?

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• 3

• 4