K

Matter Unit 3

Matter Basics

  • Definition: Anything that has mass and occupies space.

  • It cannot be created or destroyed; it can only change forms.

Pure Substances and Mixtures

  • Pure Substance: Fixed composition.

    • Elements: Cannot be chemically broken down, only a single type of atom, defined by the number of protons.

      • Atom: Fundamental unit of matter, composed of protons, neutrons, and electrons, defined by number of protons.

      • Diatomic Elements: Elements existing naturally as two atoms bound together. Examples: H2, N2, O2, F2, Cl2, Br2, I_2.

    • Compounds: Consist of 2 or more different atoms bound together (e.g., H_2O, NaCl).

  • Mixture: Variable composition.

    • Homogeneous: Uniform composition throughout (e.g., air, saltwater).

    • Heterogeneous: Not uniform composition (e.g., salad, sand + water).

Physical Properties & Changes

  • Physical Properties: Characteristics of matter that can be changed without changing its composition and are directly observable (e.g., odor, color, volume, state, density, melting point, boiling point).

  • Physical Change: A change in a physical property that retains the identity of the substance (e.g., change of state, size, or shape).

Chemical Properties & Changes

  • Chemical Properties: A substance's ability to form new substances, determining how its composition changes with other matter or energy (e.g., flammability, rusting).

  • Chemical Change: A change where the original substance is converted into one or more new substances (e.g., paper burning, iron rusting).