Particle aggregation in the context of "Rheology"

In the physical sciences, a particle (or corpuscle in older texts) is a small localized object which can be described by several physical or chemical properties, such as volume, density, or mass. They vary greatly in size or quantity, from subatomic particles like the electron, to microscopic particles like atoms and molecules, to macroscopic particles like powders and other granular materials. Particles can also be used to create scientific models of even larger objects depending on their density, such as humans moving in a crowd or celestial bodies in motion.

The term particle is rather general in meaning, and is refined as needed by various scientific fields. Anything that is composed of particles may be referred to as being particulate. However, the noun particulate is most frequently used to refer to pollutants in the Earth's atmosphere, which are a suspension of unconnected particles, rather than a connected particle aggregation.

A powder is a dry solid composed of many very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder and granular are sometimes used to distinguish separate classes of material. In particular, powders refer to those granular materials that have the finer grain sizes, and that therefore have a greater tendency to form clumps when flowing. Granulars refer to the coarser granular materials that do not tend to form clumps except when wet.

A food paste is a semi-liquid colloidal suspension, emulsion, or aggregation used in food preparation or eaten directly as a spread. Pastes are often highly spicy or aromatic, are often prepared well in advance of actual usage, and are often made into a preserve for future use. Common pastes are some fruit preserves, curry pastes, and nut pastes. Purées are food pastes made from already cooked ingredients.

Some food pastes are considered to be condiments and are used directly, while others are made into sauces, which are more liquidy than paste. Ketchup and prepared mustard are pastes that are used both directly as condiments and as ingredients in sauces.