Class 10 Science (CBSE) — Chapter-wise

Chemical Reactions and Equations

When iron rusts or wood burns, atoms aren't being destroyed—they are performing a high-speed dance of musical chairs. No new atoms are created, and none vanish. They simply change partners to form entirely new substances.

This brings us to the golden rule of chemistry: the Law of Conservation of Mass. If you start with four hydrogen atoms, you must end with four hydrogen atoms. The scale must stay perfectly balanced.

Let's look at how we write this. When hydrogen gas reacts with oxygen to make water, it looks simple. But count the oxygen atoms: we start with two on the left, but end up with only one on the right. An atom has vanished!