Colloidal particles are particles that are larger than individual molecules but small enough to remain suspended in a medium (usually a liquid or gas) without settling due to gravity. They exhibit unique properties and behaviors because of their intermediate size range. The size of colloidal particles typically falls within the nanometer (nm) range.
Here's a more detailed explanation:
1. Colloids and Colloidal Particles:
Colloids are heterogeneous mixtures where one substance is dispersed in another as small particles. The dispersed phase consists of colloidal particles. Common examples include colloidal suspensions, emulsions, and foams.
Colloidal particles are larger than individual molecules but significantly smaller than particles that can be seen with the naked eye. Their size range is typically measured in nanometers (nm).
2. Particle Size Ranges:
Nanometers (nm) are used to describe the size of colloidal particles. One nanometer is equal to one billionth of a meter.
The given range, 1 to 100 nm, encompasses the typical size range of colloidal particles. This range is chosen because particles in this size range exhibit unique properties due to their small size and high surface area.
3. Properties of Colloidal Particles:
Colloidal particles have a high surface area to volume ratio, which imparts special physical and chemical properties.
They can scatter light, a phenomenon known as the Tyndall effect, making the colloidal dispersion visible.
Brownian motion causes colloidal particles to exhibit random movement in the dispersion medium due to collisions with surrounding molecules.
4. Applications:
Colloidal systems have various applications in different fields, including medicine, industry, and research. For example, drug delivery systems, food industry stabilizers, and photographic emulsions utilize colloidal principles.
5. Comparison with Other Options:
The other options (10 to 100 pm, 1 to 100 µm, and 1 to 10 mm) represent different size scales. However, colloidal particles typically fall within the nanometer range, making option 1 (1 to 100 nm) the most accurate representation.
In summary, colloidal particles generally range from 1 to 100 nanometers, and this size range is crucial for the unique properties and behaviors observed in colloidal systems. | 
