Phase Change
Faster or Slower
Before and After
Energy Transfer
Attraction
100
What is melting
Solid to liquid
100
How is the kinetic energy of molecules changing when the molecules move faster?
The kinetic energy . . .
is increasing.
100
Which object has molecules that are moving? 
Both have molecules that are moving.
100
What does it mean when it says "transfer energy into" and "transfer energy out"
adding heat
removing heat
100
What type of attraction does a solid, liquid, and gas have?
strong
weak
Between liquid and gas, which phase has the weakest attraction?
200
What is freezing
liquid to solid
200
What happens to molecules when their kinetic energy decreases?
They move slower.
200
A student left a sealed jar of water outside her home. Water can be a solid, liquid, or gas. When she put it outside, the water was a solid. Twelve hours later, the water had changed phase and was a liquid. What happened to the water molecules?
Before the student left, the molecules were moving in place. After, the molecules were moving around each other.
200
Lily is doing a science experiment with a substance in a sealed jar. At first, the substance’s molecules are moving around each other. What will happen to Lily’s substance if she transfers energy into the substance and causes a phase change?
After the phase change, the substance’s molecules will move . . .
faster, and the substance will be a gas.
200
Divers found two substances on the bottom of the ocean. At room temperature, both substances are liquid. Scientists then transferred the same amount of energy out of both substances. When a scientist checked again, Substance 1 had changed phase, but Substance 2 had not. How are Substances 1 and 2 different?
Substance 1 has a . . .
stronger attraction between its molecules than Substance 2. Its molecules now move in place.
300
What is evaporation?
Liquid to gas
Give me an example of this.
300
Anh measured the temperature of a pond near his house. Before he left for school, the water in the pond was 18°C. When he came home from school, the temperature of the pond was higher than it was in the morning. What happened to the water molecules while he was at school?
The molecules started moving faster.
300
A scientist has a container with a substance inside. At first, the molecules in the substance move away from each other. Later, the molecules move around each other. What change did the scientist observe in the substance?
Before, the substance was a gas. Later, it was a liquid.
300
Scientists digging in a cave found an unknown substance. The scientists found that the substance’s molecules were moving around each other. The scientists increased the speed of the substance’s molecules and caused a phase change. How did the scientists do this, and how did this affect the substance?
The scientists transferred energy . . .
into the substance, and the substance changed into a gas.
300
A cook had a jar containing a sweet food and a jar containing a sour food. The image above shows the sweet and sour foods. At room temperature, both foods are liquids. The same amount of energy was transferred into both substances. Later, one of the foods had changed phase while the other had not. Which food changed phase, and how did it change?
The sweet food changed because the molecules were able to move fast enough to overcome the attraction between them. Its molecules now move away from each other.
400
What is condensation?
Gas to liquid
During this process, what happens to the molecules?
400
The fuel tank of an airplane has a device that measures the fuel’s temperature. Before the airplane took off, the temperature of the fuel was 27°C. After the airplane had been flying for one hour, the temperature of the fuel had decreased to 3°C. Which of the following must have happened to the molecules of the fuel?
The molecules started moving slower.
400
Mario is making chocolate. In part of the chocolate-making process, he changed the phase from a liquid to a solid. What happened to the molecules of chocolate when it changed phase?
Before changing phase, the molecules were moving around each other. After changing phase, they were moving in place.
400
Scientists put a sample of water into a sealed tank. Water can be a solid, liquid, or gas. At first, the water was a liquid. Then, the scientists transferred energy out of the substance, and the water changed phase. What happened to the movement of the water molecules?
After the phase change, the water molecules moved . . .
slower and started moving in place.
400
A scientist has two substances that she is testing in her lab: a pink substance and a green substance. At room temperature, both substances are liquids. The scientist transferred the same amount of energy into both substances. She finds only the pink substance changed phase. How is the pink substance different from the green substance?
The pink substance has a . . .
weaker attraction between its molecules than the green substance. Its molecules now move away from each other.
500
During condensation, what happens to the molecules
-their kinetic energy decreases
-they move slower and closer
-they start moving around each other
500
Jamil’s bicycle is made of aluminum. When are the aluminum molecules in his bicycle moving?
The aluminum molecules are . . .
always moving.
500
The diagram above describes the movement of molecules in a substance used to make fuel. What change did the fuel scientist observe in the substance?
Before the process, the substance was a liquid. After the process, it was a gas.
500
The medicine in the diagram above has molecules that are moving around each other. The doctor needs to slow down the molecules enough to cause a phase change. How will she do this, and how will this affect the medicine?
She transfers energy . . .
out of the medicine until it is a solid.
500
A scientist did a test to compare two substances: substance Q and substance R. At room temperature, both substances are liquid. When the scientist transferred the same amount of energy out of both substances, only one substance changed phase while the other did not. Which substance changed phase, and how did it change?
Substance Q changed phase because the attraction of the molecules was able to overcome their slower movement. Its molecules now move in place.