NCERT Class 9 Science Chapter 9 Atomic Foundations of Matter Solutions
NCERT Class 9 Science Chapter 9 Atomic Foundations of Matter Solutions Think It Over (Page No. 162) 1. Water can be obtained from various sources. Are all these samples of water chemically identical? Answer: Yes, all samples of purified water are chemically identical, regardless of their source — whether from rivers, borewells, rainwater, or the ocean. This is explained by the Law of Constant Proportions (Proust’s Law), which states that a compound always contains the same elements combined in a fixed ratio by mass. Water always contains hydrogen and oxygen in a mass ratio of 1:8, no matter where it comes from. So if 9 g of purified water is decomposed, it always gives 1 g of hydrogen and 8 g of oxygen. 2. Oxygen is sometimes represented as O and sometimes as O₂. What is the difference between these symbols? Answer: O represents a single oxygen atom — it is just one atom of the element oxygen. It is an isolated atom and does not exist independently under normal conditions. O₂ represen...