Pure Substances
Pure substances are materials made of only one type of particle—atom or molecule—throughout, giving them a fixed, uniform composition and consistent, predictable properties. In Amplify Science (California) Grade 7, Chapter 1: Properties and Atoms, students learn to identify pure substances and distinguish them from mixtures as the first step in chemical analysis.
Key Concepts
A pure substance is made of only one type of particle (atom or molecule) throughout. Whether you look at a spoonful or a bucketful, the composition is uniform.
This consistency means a pure substance has a fixed set of properties. Water is always H₂O, and Iron is always Fe.
Common Questions
What is a pure substance?
A pure substance is made entirely of one type of atom or molecule. Whether you have a small or large sample, the composition is the same throughout. Examples include water (H2O) and iron (Fe).
Why do pure substances have consistent properties?
Pure substances have consistent properties because they are made of only one type of particle in a fixed arrangement. Every sample of water boils at 100°C and freezes at 0°C at standard pressure.
How do you identify if something is a pure substance?
A pure substance has uniform composition throughout and fixed, predictable properties. If a material's properties change from sample to sample, it is likely a mixture, not a pure substance.
Where are pure substances covered in Amplify Science Grade 7?
Pure substances are covered in Amplify Science (California) Grade 7, Chapter 1: Properties and Atoms.