Background: As Figure above shows, the distance between particles is much smaller for the solid and liquid states than for the gas state. In the solid state, particles are fixed in place, while particles are more free to move in the liquid and gas states. The particles in the solid and liquid states “stick together,” but in the gas state, they move freely about the container. In general, it requires energy to separate individual particles. If we want to make a solid adopt a liquid form, we can add energy in the form of heat, increasing the temperature of the substance. Conversely, if we want to convert a substance from a gas to a liquid or from a liquid to a solid, we remove energy from the system and decrease the temperature. Pressure also plays an important role in changes of state, which will be discussed later on. We will study these difference in greater detail in the chapter States of Matter.

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Are particles in the ice more or less freely able to move than in the water?
Answer: less

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Are particles in the water more or less freely able to move than in the ice?
Answer: more

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Is energy currently increasing or decreasing in the block of ice?
Answer: increasing

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Is energy currently increasing or decreasing in the pitcher of water?
Answer: decreasing

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Is the block of ice transforming into a liquid, gas or solid state?
Answer: liquid

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Is the pitcher of water transforming into a liquid, gas or solid state?
Answer: solid

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Would the water or the ice require more energy to transform into a gas?
Answer: ice

Situation: Matt is preparing food for a dinner party in his kitchen. His guests will be arriving shortly, so he fills up a pitcher with some water and puts it in the freezer to cool it down. He then takes a solid block of ice out of his freezer that he is planning to carve into a sculpture of some kind. Before he can start sculpting, there is a knock on his door that he must answer.

Question: Would the water or the ice require less energy to transform into a gas?
Answer: water