This document discusses how materials can be sorted into groups based on their properties. It describes several properties used to classify materials, including appearance, hardness, solubility, transparency, and gives examples for each property. The key properties discussed are: - Appearance (lustrous vs dull) - Hardness (hard vs soft materials like iron vs cotton) - Solubility (soluble vs insoluble in water) - Transparency (transparent, opaque, translucent materials like glass, wood, oily paper) Materials can be grouped based on similarities and differences in their properties, which allows for convenient study and understanding of materials.