Benchmark Review: States of Matter and Phase Changes

Benchmark Review, 2022

States of Matter &

Phase Changes

Solid

In a solid, particles are packed tightly together so they don't move much, but are dense. The electrons of each particle are constantly in motion, giving the atoms a small vibration, but they are fixed in their position.

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Solids have a definite shape, as well as mass and volume, and do not conform to the shape of the container in which they are placed. 

Liquid

In a liquid, the particles are more loosely packed than in a solid, but closely enough that it is not easily compressible.

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The particles are able to flow around each other, giving the liquid an indefinite shape. Therefore, the liquid will conform to the shape of its container.

Gas

In a gas, the particles have a great deal of space between them, so they move easily, and have high kinetic energy (energy of movement).

Gas

A gas has no definite shape or volume. If unconfined, the particles of a gas will spread out indefinitely (forever). However, if confined, the gas will expand to fill its container.

Multiple Choice

A substance with particles that vibrate but stay in the same position is a ___.

• solid

• liquid

• gas

• plasma

Multiple Choice

Of the 3 states listed below, which has the fasted moving particles?

• solid

• liquid

• gas

Multiple Choice

In which state of matter do the particles move the slowest?

• solid

• liquid

• gas

Multiple Choice

The particles are closest together in a ___________.

• solid

• liquid

• gas

• plasma

Multiple Choice

Definite shape and definite volume

• solid

• liquid

• gas

• solid, liquid and gas

Multiple Choice

Particles slide past each other

• solid

• liquid

• gas

• solid, liquid and gas

Multiple Choice

The diagram to the left represents particles in a gas. (The length of the arrow represent the amount of particle energy.) Which of the diagrams below best represents the particles after the gas is heated?

Phase Changes

Phase changes are changes in the state of matter.

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For example: when a solid melts and becomes a liquid, that is a phase change.

What causes a phase change?

The single most important factor involving a phase change is heat.

Recall that a phase change graph is used to show temperature change in a substance as it absorbs or releases heat energy.

Phase Change Graphs

​Reminders...

​The segments that are diagonal

( / ) are where the temperature is changing = state of matter

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​-Horizontal (flat) segments are where heat energy is still being absorbed BUT temperature is no longer changing = a phase change occurring

Multiple Choice

In this phase change graph, which line segments represent states of matter?

• A, C, and E

• B and D

Multiple Choice

On the phase change graph, which letter represents the substance as a gas?

• A

• B

• C

• D

• E

1. We know that that states of matter are the slanted lines because that is where the temperature is changing.

2. The state of matter that has the highest temperature has to be the gas.

3. Therefore, the letter E represents the substance as a gas.

Where's the Gas?

Multiple Select

Where on the graph are phase changes taking place?

• between points A and B

• between points B and C

• between points C and D

• between points D and E

Recall that as a substance is absorbing heat, the only time the temperature will stop changing is when a phase change is occurring.

The only segments where the temperature is not changing is between B & C and between D & E.

Phase Changes = no change in temp

Multiple Choice

Which segment indicates a gas increasing in temperature?

• A

• B

• C

• D

• E

Multiple Choice

If the substance is being cooled, what change of state (phase change) is represented by line segment B?

• melting

• freezing

• boiling

• condensing

• If the substance is being cooled, then the temperature is decreasing, which means we have to read the graph from right to left. (from high temp to low temp)

• ​Therefore, the phase changes will be exothermic, which are the cooling phase changes.

• If we know that C is a liquid and A is a solid, then B is the phase change that occurs from liquid to solid- which is FREEZING.

Exothermic phase changes:

(Removing heat energy)

Multiple Choice

If the substance is being cooled, what change of state (phase change) is represented by line segment D?

• melting

• freezing

• boiling

• condensing

• If the substance is being cooled, then the temperature is decreasing, which means we have to read the graph from right to left. (from high temp to low temp)

• ​Therefore, the phase changes will be exothermic, which are the cooling phase changes.

• If we know that E is a gas and C is a liquid, then D represents the phase change that occurs from gas to liquid- which is condensation.

Exothermic phase changes:

(Removing heat energy)