The Second Law and Entropy

Question 1

The figure compares the same gas before and after a partition is removed. Which state has the higher entropy?

Accepted Answer

State 2, because the gas can occupy more positions and has more possible arrangements.

Answer

State 1, because the gas particles are closer together.

Answer

State 1, because the partition keeps the system more organized.

Answer

The states have equal entropy because no gas particles were added or removed.

Question 2

The figure shows dye in a beaker at two times. Which state has the higher entropy?

Accepted Answer

State 2, because the dye particles are spread through more of the water.

Answer

State 1, because the dye color is more concentrated.

Answer

State 1, because the dye particles have not mixed with the water.

Answer

The states have equal entropy because the same amount of dye is present.

Question 3

Two identical metal blocks are insulated from the room. The figure shows an initial and final state. Which state has the higher total entropy of the two blocks?

Accepted Answer

State 2, because thermal energy has spread from the hotter block to the colder block.

Answer

State 1, because the blocks have a larger temperature difference.

Answer

State 1, because one block stores more useful thermal energy.

Answer

The states have equal entropy because the total energy of the blocks is unchanged.

Question 4

The figure compares salt before and after it dissolves in water. Which state has the higher entropy for the salt-water system?

Accepted Answer

State 2, because the ions and water molecules are mixed in many more arrangements.

Answer

State 1, because the salt crystals have a regular pattern.

Answer

State 1, because the salt is easier to see before dissolving.

Answer

The states have equal entropy because no atoms were destroyed.

Question 5

The figure shows perfume vapor just after spraying and later in the same closed room. Which state has the higher entropy?

Accepted Answer

State 2, because the vapor is dispersed through a much larger region.

Answer

State 1, because the vapor cloud is easier to locate.

Answer

State 1, because the molecules are closer together near the spray.

Answer

The states have equal entropy because the room volume did not change.

Question 6

The figure compares the same wax sample as a solid and as a liquid at its melting temperature. Which state has the higher entropy?

Accepted Answer

State 2, because liquid molecules can move past one another in more arrangements.

Answer

State 1, because the solid has a definite shape.

Answer

State 1, because melting keeps the temperature constant.

Answer

The states have equal entropy because the sample has the same mass.

Question 7

The figure shows the same amount of gas in two insulated rigid containers of different volume. Which state has the higher entropy?

Accepted Answer

State 2, because the same gas particles are spread over a larger volume.

Answer

State 1, because the pressure is higher in the smaller container.

Answer

State 1, because the particles collide more often with the walls.

Answer

The states have equal entropy because the number of particles is the same.

Question 8

The figure compares water vapor spread through a jar with the same water condensed into liquid drops. Which state has the higher entropy for the water?

Accepted Answer

State 1, because vapor molecules are spread farther apart and have more arrangements.

Answer

State 2, because liquid drops are easier to see.

Answer

State 2, because condensation releases energy to the surroundings.

Answer

The states have equal entropy because both contain water molecules.

Question 9

A 70 °C metal spoon is placed on a 22 °C lab table. Nothing else is done. What happens on its own?

Accepted Answer

Energy transfers from the spoon to the table until their temperatures become closer.

Answer

Energy transfers from the table to the spoon until the spoon gets hotter.

Answer

No energy transfers because both objects are solids.

Answer

Energy transfers back and forth equally while the spoon stays at 70 °C.

Question 10

An ice cube at 0 °C is dropped into tea at 60 °C in an insulated cup. Which direction is spontaneous?

Accepted Answer

Energy transfers from the tea to the ice, warming and melting the ice while cooling the tea.

Answer

Energy transfers from the ice to the tea, making the tea hotter.

Answer

Energy transfers only after the ice and tea reach the same temperature.

Answer

No energy transfers because the insulated cup blocks all heat flow inside.

Question 11

A tiny amount of gas is released in one corner of an evacuated chamber. Which outcome happens on its own?

Accepted Answer

The gas spreads out to fill the chamber.

Answer

The gas stays packed in the corner because no energy was added.

Answer

The gas gathers into a smaller clump at the center.

Answer

The gas separates into hot particles on one side and cold particles on the other.

Question 12

A drop of ink is placed gently in still water. After a long time, which process is expected without stirring?

Accepted Answer

The ink disperses through the water.

Answer

The ink collects back into one small drop at the surface.

Answer

The water separates into clear and dark layers forever.

Answer

The ink disappears because its energy is destroyed.

Question 13

A glass falls and shatters on the floor. Which statement best matches the second law?

Accepted Answer

The pieces will not reassemble into a glass on their own, even though energy is conserved.

Answer

The pieces must reassemble because the first law conserves energy.

Answer

The pieces cannot move because shattering destroys energy.

Answer

The pieces reassemble if the room is at a uniform temperature.

Question 14

A bicycle brakes to a stop, warming the brake pads and rim. What reverse process does the second law rule out as spontaneous?

Accepted Answer

Warm brakes cooling while making the bicycle start moving again.

Answer

A rider pedaling to make the bicycle speed up.

Answer

Brake pads transferring energy to cooler surrounding air.

Answer

Friction converting organized motion into thermal energy.

Question 15

Equal masses of water at 80 °C and 20 °C are poured into an insulated container. Which final trend occurs on its own?

Accepted Answer

The water mixes toward one intermediate temperature.

Answer

The hot water gets hotter while the cold water gets colder.

Answer

The mixture separates into 80 °C water on top and 20 °C water below.

Answer

The temperatures stay unchanged because total energy is conserved.

Question 16

A refrigerator moves energy from its cold interior to the warmer kitchen. What must be true for this to happen?

Accepted Answer

Work must be supplied to the refrigerator.

Answer

It happens unaided because cold objects naturally warm hot objects.

Answer

It violates the second law whenever it happens.

Answer

It requires the kitchen to be colder than the refrigerator interior.

Question 17

A valve opens between a high-pressure air tank and an empty rigid chamber. What happens spontaneously?

Accepted Answer

Air flows into the empty chamber and spreads out.

Answer

Air in the empty chamber flows into the tank first.

Answer

All air remains in the tank because the total energy is fixed.

Answer

Air separates so that faster molecules enter the chamber and slower molecules stay behind.

Question 18

A sealed bottle of strong scent is opened in one corner of a classroom. What will students across the room eventually notice?

Accepted Answer

The scent spreads through the room as vapor molecules disperse.

Answer

The scent stays near the bottle unless the bottle is heated above 100 °C.

Answer

The scent molecules gather into a visible liquid drop in the opposite corner.

Answer

The scent disappears because spreading out destroys the molecules.

Question 19

A cold aluminum can at 5 °C is placed in air at 24 °C. Which process happens without a device doing work?

Accepted Answer

Energy transfers from the warmer air to the colder can.

Answer

Energy transfers from the can to the air until the can is below 0 °C.

Answer

The can makes the room warmer by giving energy to hotter air.

Answer

No energy transfers because air is a thermal insulator.

Question 20

A cup at 45 °C sits in a 22 °C room. Which change would not happen on its own?

Accepted Answer

The room transfers energy to the cup so the cup rises above 45 °C.

Answer

The cup transfers energy to the room as it cools.

Answer

The cup and nearby air move toward thermal equilibrium.

Answer

Some energy from the cup becomes more spread out in the surroundings.

Question 21

Which statement gives the second law of thermodynamics in entropy terms?

Accepted Answer

The total entropy of a system plus its surroundings never decreases in a real process.

Answer

The total energy of a system plus its surroundings is always zero.

Answer

The entropy of every single part of a system must always increase.

Answer

The temperature of an isolated system must always decrease.

Question 22

A proposed engine takes energy from one warm reservoir and turns all of it into useful work with no other effect. Why is this impossible?

Accepted Answer

It would require a total entropy decrease.

Answer

It would violate conservation of energy because work is not energy.

Answer

It would require the reservoir temperature to be measured in Celsius.

Answer

It would make the engine more than 100% massive.

Question 23

In this course, what does entropy describe qualitatively?

Accepted Answer

How spread out energy and matter are among possible microscopic arrangements.

Answer

How much total energy a system has, whether useful or not.

Answer

How hot a substance feels to a hand touching it.

Answer

How much mass is contained in a fixed volume.

Question 24

How does the second law differ from the first law of thermodynamics?

Accepted Answer

The first law tracks energy conservation, while the second law limits the direction of real processes.

Answer

The first law applies only to solids, while the second law applies only to gases.

Answer

The first law says entropy increases, while the second law says energy is conserved.

Answer

The first law forbids heat flow, while the second law requires temperature to stay constant.

Question 25

Which heat-transfer event is forbidden as the only spontaneous result?

Accepted Answer

Energy flows from a colder object to a hotter object.

Answer

Energy flows from a hotter object to a colder object.

Answer

Two objects at different temperatures approach the same temperature.

Answer

A hot object cools while its cooler surroundings warm.

Question 26

Which statement about a local decrease in entropy is correct?

Accepted Answer

It can happen if the entropy of the surroundings increases by a larger amount.

Answer

It is impossible anywhere because entropy can never decrease locally.

Answer

It happens only when energy is destroyed in the local system.

Answer

It proves the second law applies only to isolated gases.

Question 27

Two objects in contact have the same temperature. What does the second law imply about heat flow between them?

Accepted Answer

There is no net spontaneous heat flow from one to the other.

Answer

Heat flows from the object with greater mass to the object with smaller mass.

Answer

Heat flows from the object with more total internal energy to the other.

Answer

Heat flows back and forth in a way that makes one object steadily hotter.

Question 28

Which statement is true for entropy in real irreversible processes?

Accepted Answer

Total entropy increases rather than being conserved like energy.

Answer

Entropy is conserved exactly in every real process.

Answer

Entropy decreases whenever temperature increases.

Answer

Entropy is the same quantity as thermal energy.

Question 29

A block of ice at 0 °C melts completely to liquid water at 0 °C. Considering only the water, how does its entropy change?

Accepted Answer

It increases because liquid water molecules can occupy more arrangements than molecules fixed in ice.

Answer

It decreases because liquid water takes up slightly less volume than ice.

Answer

It stays the same because the temperature remains 0 °C.

Answer

It stays the same because the mass is unchanged.

Question 30

Liquid water in a freezer becomes solid ice. Considering only the water, what happens to its entropy?

Accepted Answer

It decreases because the molecules become locked into a more ordered solid structure.

Answer

It increases because the freezer uses electrical energy.

Answer

It stays the same because water molecules are still H2O.

Answer

It increases because colder objects always have higher entropy.

Question 31

Sugar dissolves completely in a cup of water. For the sugar-water system, which entropy description is best?

Accepted Answer

Entropy increases because sugar particles become spread through the water.

Answer

Entropy decreases because the sugar is no longer visible.

Answer

Entropy stays the same because the sugar's mass is conserved.

Answer

Entropy decreases because dissolving makes the water taste uniform.

Question 32

Water vapor on a cold mirror condenses into liquid droplets. Considering only the water, how does entropy change?

Accepted Answer

It decreases because the molecules become less spread out in the liquid.

Answer

It increases because droplets are easier to see than vapor.

Answer

It stays the same because vapor and liquid have the same chemical formula.

Answer

It increases because cold surfaces always add entropy to nearby water.

Question 33

A gas expands from 1 L to 4 L at the same temperature. How does the gas's entropy change?

Accepted Answer

It increases because the gas particles have more volume and more possible positions.

Answer

It decreases because the pressure becomes lower.

Answer

It stays the same because the temperature is unchanged.

Answer

It decreases because each particle has less space to collide with others.

Question 34

A shallow puddle evaporates into water vapor in warm air. Considering the water molecules, what happens to entropy?

Accepted Answer

It increases because the molecules spread from a liquid surface into the air.

Answer

It decreases because the puddle becomes smaller.

Answer

It stays the same because evaporation does not change the molecules into a new substance.

Answer

It decreases because vapor is invisible.

Question 35

A barrier between helium and neon gases is removed in a sealed container, and the gases mix. What happens to the entropy of the gases?

Accepted Answer

It increases because each gas spreads into space that was previously unavailable to it.

Answer

It decreases because two gases become one uniform mixture.

Answer

It stays the same because the container is sealed.

Answer

It decreases because helium and neon do not chemically react.

Question 36

Salt ions in a saturated solution join a growing crystal. Considering only those ions in the crystal, what happens to their entropy?

Accepted Answer

It decreases because the ions take fixed positions in an ordered lattice.

Answer

It increases because the crystal is easier to see.

Answer

It stays the same because the ions keep the same electric charges.

Answer

It increases because all solid formation releases energy.

Question 37

A freezer turns liquid water at 20 °C into ice at −8 °C while its coils warm the kitchen. Why is the second law not broken?

Accepted Answer

The kitchen gains more entropy than the water loses.

Answer

The second law does not apply below 0 °C.

Answer

The water's entropy actually increases when it freezes.

Answer

Machines are allowed to violate the second law for short times.

Question 38

A plant builds ordered sugar molecules and tissues using sunlight. Why does this not violate the second law?

Accepted Answer

The plant's local ordering is accompanied by a larger entropy increase in the surroundings.

Answer

Living things are exempt from thermodynamics.

Answer

Photosynthesis destroys entropy instead of moving energy.

Answer

The second law applies only to machines, not organisms.

Question 39

A running refrigerator has its door left open inside a closed, insulated kitchen. What happens to the kitchen's air temperature over time?

Accepted Answer

It rises, because the refrigerator only moves heat around the room and its work input also becomes heat.

Answer

It falls, because the open refrigerator cools the whole room.

Answer

It stays the same, because the heat taken in equals the heat released.

Answer

It falls until the room matches the temperature inside the refrigerator.

Question 40

A cell uses energy from food to build a highly ordered protein. Why is the total process consistent with the second law?

Accepted Answer

Building the protein lowers local entropy, but metabolism releases heat and waste that increase surrounding entropy more.

Answer

Protein molecules are too small for entropy to apply.

Answer

The second law says ordered structures cannot form anywhere.

Answer

Food energy is not part of the system plus surroundings.

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The Second Law and Entropy

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The Second Law and Entropy

Ways to Play

Device Games: Students play on their phones

Blast Go

Zombie Escape

Avalanche

Maze Blast

Cave Climb

Blast Out

Mystery Auction

Tour Guide

Food Truck Rush

Tug of War

Alien Blast

Glacier Rush

Board Games: Teacher-led, projected to the class

Like what you see?

More like this

Bug Blast

BlastRace

BlastQuiz

BlastBoard

Seek & Destroy

Mystery Blast

Checkers

Texas Hold 'Em

Da Bomb

Castle Siege

Hot Potato

Market Mayhem

King of the Hill

Bank Heist

Top Corner