- + Sodium atom (Na) Chlorine atom (Cl) Sodium Chloride NaCl Sodium ion (Na+) Chlorine ion (Cl-)

CLASSIFYING MATTER

Describe the difference between element and compound, and atom and molecule. Understand the various descriptions of matter. Understand the information in a chemical formula. KEY WORDS Pure Mixture Compound Molecule Heterogeneous Homogeneous Diatomic Chemical formula Subscript

Anything that has mass and takes up space, or volume. Matter: Anything that has mass and takes up space, or volume.

Pure substance The particles that make up a substance are all the same kind. Mixture Substance contains more than one kind of particle.

Elements The simplest form of a material; an atom is the smallest particle of an element. Compounds The simplest form of any material containing two or more elements chemically bonded together. A molecule is the smallest particle of a compound.

Element: Silver– all atoms are pure silver. Compound: Salt – all molecules are pure sodium chloride. Possible to have a molecule of the same atoms: Oxygen gas – O2 Hydrogen gas – H2 Molecules like this are diatomic – “two atoms.”

Heterogeneous mixture Particles are not evenly distributed. Individual particles can be found. Sand and water Pizza

Homogeneous mixture Particles of are evenly distributed – “solution” Cannot easily separate different parts. Salt and water Coke

All matter is either pure or a mixture. Pure matter - elements (atoms) or compounds (molecules). Mixtures - homogenous (joined) or heterogeneous (separate). Homogenous mixtures are called “solutions”