1. Rearrangement of Atoms: The fundamental building blocks of matter, atoms, are rearranged to form new substances with different properties. This rearrangement involves breaking existing chemical bonds and forming new ones.

2. Energy Change: Chemical changes always involve a change in energy. Energy can be released (exothermic reaction, like burning wood) or absorbed (endothermic reaction, like photosynthesis).

3. Formation of New Substances: The result of a chemical change is the formation of new substances with different chemical compositions and properties than the original substances. For example, when iron rusts, it forms iron oxide (rust) with different properties than the original iron.

4. Difficult to Reverse (Sometimes): While some chemical changes are reversible (like dissolving sugar in water), many are difficult or impossible to reverse easily. For example, once wood burns, it's hard to get the original wood back.

Key Points:

* Chemical changes are permanent: They result in the formation of new substances with new properties.

* Chemical changes involve the breaking and formation of bonds: This is the essence of the rearrangement of atoms.

* Chemical changes are not always obvious: Sometimes, the changes are subtle and require observation or testing to detect.

Examples of Chemical Changes:

* Burning wood

* Cooking an egg

* Rusting of iron

* Photosynthesis

* Digestion of food

Let me know if you have any other questions!