A chemical reaction is when reactants turn into new products because atoms rearrange and form new bonds, while no atoms are created or destroyed. It usually involves an energy change too, such as heat being released or absorbed.

What changes

  • Old bonds in the reactants break.
  • Atoms rearrange.
  • New bonds form to make different substances.
  • The total number of atoms stays the same, even though they are grouped differently.

What you may notice

  • Temperature may change.
  • Gas bubbles may form.
  • A solid might appear.
  • Light or color changes can happen.

Simple example

If vinegar and baking soda react, they form new substances, including carbon dioxide gas, which is why bubbling happens. The original materials do not simply disappear; their atoms are reorganized into new products.

Mini takeaway

In short, a chemical reaction is a rearrangement of atoms that creates new substances and often changes energy in the process.

TL;DR: Chemical reactions break and remake bonds, rearrange atoms, and produce new substances with the same atoms as before.