Key Idea.
Section 1
High Energy and Empty Space
The molecular structure of a gas is defined by chaos and space. Gas molecules move at high speeds in random directions, breaking away from their neighbors completely.
Because they move so freely, vast amounts of empty space exist between the particles. This high-speed scattering explains why a gas expands to fill any container—the molecules simply keep moving until they hit a wall.
Section 2
Same Molecules, Different States
A phase change alters the form of a substance, not its identity. Water ice, liquid water, and water vapor are all made of the exact same molecules.
The molecule itself never changes; it does not melt or expand. Instead, the arrangement and movement of the molecules change. Determining the state of matter is about observing how the molecules interact, not what they are made of.
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Section 1
High Energy and Empty Space
The molecular structure of a gas is defined by chaos and space. Gas molecules move at high speeds in random directions, breaking away from their neighbors completely.
Because they move so freely, vast amounts of empty space exist between the particles. This high-speed scattering explains why a gas expands to fill any container—the molecules simply keep moving until they hit a wall.
Section 2
Same Molecules, Different States
A phase change alters the form of a substance, not its identity. Water ice, liquid water, and water vapor are all made of the exact same molecules.
The molecule itself never changes; it does not melt or expand. Instead, the arrangement and movement of the molecules change. Determining the state of matter is about observing how the molecules interact, not what they are made of.
Book overview
Jump across lessons in the current chapter without opening the full course modal.
Continue this chapter