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100
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.
100
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.
100
weaker attraction between its molecules than the green substance. Its molecules now move away from each other.
100
Jamil’s bicycle is made of aluminum. When are the aluminum molecules in his bicycle moving?
The aluminum molecules are . . .
always moving.
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
A glass of water and the ocean. Which object has molecules that are moving?
Both
200
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.
200
How is the kinetic energy of molecules changing when the molecules move faster?
The kinetic energy . . .
is increasing.
300
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 happens to molecules when their kinetic energy decreases?
They move slower.
300
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.
300
A truck was carrying a substance in a tank. The molecules of that substance were moving away from each other. The truck parked overnight in a place where energy transferred out of the substance. In the morning, the substance was a gas. How were the molecules moving in the morning? Explain why the molecules were moving that way after energy was transferred out of them.
the molecules were moving away from each other
It did not change phase.
400
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.
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
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.
400
A mining crew extracted two different types of minerals from underground. Then, they transferred the same amount of energy into both minerals. Why did mineral A change while mineral B stayed the same?
A changed Phase, B higher attraction
500
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.
500
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.
500
Substance Q changed phase because the attraction of the molecules was able to overcome their slower movement. Its molecules now move in place.
500
What happens to molecules when their kinetic energy decreases?
They move slower.