VOCAB 1
when matter changes to from one state (solid, liquid, gas, plasma) to another
phase change
the total kinetic energy of all the molecules that make up a sample
thermal energy
A car mechanic had a sealed bucket containing a substance in the gas phase. She left the bucket outside over the weekend. When she returned, the substance had changed phase, and the substance was in the liquid phase. What happened to the molecules of this substance?
Before the mechanic left, the molecules were moving away from each other. When she returned, they were moving around each other.
The image above shows information about two different substances in sealed containers. At room temperature, both substances are liquids. A scientist transfers the same amount of energy into both substances. One substance changes phase, but the other does not. Which chemical changed phase, and why did it change?
Substance A changed phase because its molecules were able to move fast enough to overcome the attraction between them. Its molecules now move away from each other.
How many moons does Saturn have?
146
a measure of how hot or cold something is
temperature
the relative size of things
scale
A chef finds a sealed container consisting of an ingredient that goes into his restaurant’s secret sauce. The ingredient’s molecules are moving in place. What will happen if the chef causes the ingredient to change phase by transferring energy into it? After the phase change, the ingredient’s molecules will move . . .
faster, and the ingredient will be a liquid.
A student left a jar of water outside his home. Water can be a solid, liquid, or gas. When he put the jar outside, the water was liquid. Twelve hours later, the water had changed phase and was a gas. What happened to the water molecules?
When the student left the jar outside, the molecules were moving around each other. Later, the molecules were moving away from each other
An Earth scientist brought an unknown substance from underground back to her lab. The substance was in the gas phase, and was put into a sealed tank as shown above. She slowed down the molecules inside the tank and the substance changed phase. How did she do this, and how did it affect the molecules? She transferred energy . . .
out of the substance, and the molecules moved around each other.
to provide evidence that goes against a claim
refute
a noticeably different form or state of the same substance
phase
Workers find two substances. One is a toxic chemical. The other is a safe chemical. Both chemicals are liquids at room temperature. As a test, the workers transfer the same amount of energy out of the two containers and find that only the toxic chemical changes phase. How is the toxic chemical different from the safe chemical? The toxic chemical has a . . .
stronger attraction between its molecules than the safe chemical. Its molecules now move in place.
Refrigerators are able to transfer energy out of a substance. At first, the substance is a gas. The refrigerator changes the phase of the substance by transferring energy out of it. How does this change affect the substance’s molecules? After the phase change, the molecules move . . .
slower, and they move around each other
Two different cars, the Model S and Model T, use different substances in their engines. The image above shows the two substances. At room temperature, both substances are liquids. A car mechanic transferred the same amount of energy out of the two containers, but only one substance changed phase. Which car’s substance changed phase, and how did it change?
The Model T’s substance changed phase because the attraction of the molecules was able to overcome their slower movement. Its molecules now move in place.
a group of atoms joined together in a particular way
molecule
a pull between two molecules that is always the same for a substance
molecular attraction
Cesar and Ming were investigating a see-through container of water. Water can be a solid, liquid, or gas. At first, Cesar and Ming said the water molecules were moving in place. Later, the water molecules were moving around each other. What change did they observe to the water?
At first, the water was a solid. Later, it was a liquid.
Detectives find two substances at a crime scene. One is a poison, and the other is a cleaning chemical. At room temperature, both substances are liquids. To test the substances, the detectives transfer the same amount of energy into both substances, but only the cleaning chemical changes phase. How is the cleaning chemical different from the poison? The cleaning chemical has a . . .
weaker attraction between its molecules than the poison. Its molecules now move away from each other.
An allergy medicine is usually stored in a cabinet at room temperature where its molecules move around each other. By mistake, an intern transferred energy into the medicine. After one hour, the intern found the medicine and noticed that it was a liquid. How were the molecules moving when the intern found the medicine? Explain why the molecules were moving this way after the intern transferred energy into the medicine.
When the intern found the medicine, the molecules were moving around each other because that is how the molecules of a liquid move. This means the molecules’ freedom of movement didn’t change after the intern transferred energy into the medicine. However, because there was energy transferred into the medicine, the kinetic energy of the molecules did change—the energy increased and the molecules were moving faster. The reason the energy transfer didn’t cause the molecules’ freedom of movement to change is because the molecules didn’t speed up enough to overcome the attraction between them.
the energy that an object has because it is moving
kinetic energy
the way molecules in a substance move around relative to each other
freedom of movement
A company uses a substance that is a solid under normal conditions. This substance will be used in extreme conditions, which could make the substance’s molecules move faster and cause a phase change. How would this phase change occur, and how would the molecules of the substance be affected under these extreme conditions? Energy would be transferred . . .
into the substance, and its molecules would move around each other.
Scientists have a container of water. Water can be a solid, liquid, or gas. At first, the water molecules in the container were moving around each other. Later, the water molecules were moving in place. What change did the scientists observe?
At first, the water was a liquid. After, it was a solid.
A certain type of ship has two tanks in its engine. Each tank contains a different type of fuel. When the engine turns on, the same amount of energy is transferred out of both fuels as shown in the diagram below. Why did fuel 1 change phase, but fuel 2 stayed the same? Explain what happened to the molecules of both fuels.
: The molecules in both substances started moving slower when energy was transferred out because their kinetic energy decreased. Fuel 1 changed phase because enough energy was removed from it for the attraction pulling the molecules together to overcome their kinetic energy, but fuel 2 has a lower attraction, so the molecules didn’t slow down enough for the attraction to overcome their kinetic energy. When fuel 1 changed phase, the molecules went from moving away from each other to moving around each other. Since Fuel 2 did not change phase, the molecules were moving away from each other before and after energy was added.