Same Molecules, Different States
Same molecules, different states demonstrates that water ice, liquid water, and water vapor are all made of identical H2O molecules—what changes is the arrangement and movement of those molecules, not their chemical identity. In Amplify Science (California) Grade 7, Chapter 1: Describing Phase Change at Two Scales, students learn to analyze states of matter at the molecular level.
Key Concepts
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.
Common Questions
Are ice, liquid water, and steam made of the same molecules?
Yes, all three are made of identical H2O molecules. The difference between solid ice, liquid water, and water vapor is how the molecules are arranged and how freely they move, not what they are.
What changes during a phase change?
During a phase change, the arrangement and movement of molecules change, but the molecules themselves remain chemically identical. Molecules in a solid vibrate in place, in a liquid they slide, and in a gas they move freely and far apart.
How do you determine the state of matter of a substance?
You determine the state of matter by observing how molecules interact—whether they vibrate (solid), slide (liquid), or move freely (gas)—not by the chemical identity of the molecules.
Where is this concept taught in Amplify Science Grade 7?
Same molecules, different states is covered in Amplify Science (California) Grade 7, Chapter 1: Describing Phase Change at Two Scales.