Solids:
1. Sand: Primarily composed of silicon dioxide (SiO2), sand does not dissolve in water.
2. Rocks: Most rocks are made of minerals like quartz, feldspar, and mica, which are generally insoluble in water.
3. Plastic: Most plastics, like polyethylene, polypropylene, and PVC, are not water-soluble.
4. Wood: Wood is composed of cellulose and lignin, which are largely insoluble in water.
5. Iron: Iron metal is not soluble in water, although it can react with water in the presence of oxygen to form rust.
6. Sulfur: Elemental sulfur is insoluble in water.
7. Diamond: A form of pure carbon, diamond is extremely hard and insoluble in water.
8. Glass: While some specific types of glass can be slightly soluble, in general, glass is considered insoluble in water.
9. Oil: Oil and water don't mix. Oils like vegetable oil, mineral oil, and petroleum are hydrophobic (water-repelling).
Other:
10. Air: Air is a mixture of gases, primarily nitrogen and oxygen, which do not dissolve significantly in water.
11. Grease: Greases, like cooking oil, are hydrophobic and insoluble in water.
12. Wax: Waxes, such as beeswax and paraffin wax, are insoluble in water.
13. Rubber: Rubber is generally insoluble in water.
14. Clay: Clay minerals, while they can absorb water, are not truly soluble in it.
15. Chalk: Chalk is primarily composed of calcium carbonate, which is insoluble in water.
Important Note: "Insoluble" is a relative term. Some substances considered insoluble may dissolve to a tiny degree in water. This is why we often talk about "slightly soluble" substances.
