Elemental copper would be a pure substance.
AppearanceClear, transparent and homogeneousCloudy, heterogeneous, at least two substances visibleParticle Sizemolecule in sizelarger than 10,000 AngstromsEffect of Light Tyndall Effectnone -- light passes through, particles do not reflect lightvariableEffect of Sedimentationnoneparticles will eventually settle ou
Buffers - mixtures of conjugate acid and conjugate base at ±1 pH unit from pH = pKa. Resistant to changes in pH in response to small additions of H+ or OH-. ... Polyprotic acids - dissociation of each H+ can be treated separately if the pKa values are different
1. Dry Ice (solid carbon dioxide)
2. Iodine
3. Arsenic
4. Naphthalene