Key Characteristics:
* New Bonds Form: The atoms of the original substances break their existing bonds and form new bonds with each other.
* New Substances: This bond rearrangement results in the creation of entirely new substances with unique chemical formulas and properties.
* Energy Change: Chemical reactions involve either the absorption or release of energy, often in the form of heat or light.
* Irreversible (usually): While some chemical reactions can be reversed under specific conditions, many are irreversible, meaning the original substances cannot be easily recovered.
Examples:
* Burning Wood: Wood (cellulose) reacts with oxygen to form carbon dioxide, water, and ash. The heat and light released are evidence of energy change.
* Baking a Cake: Flour, sugar, eggs, and other ingredients undergo chemical changes during baking, resulting in a cake with a different texture, taste, and appearance.
* Rusting Iron: Iron reacts with oxygen and water to form iron oxide (rust), a new substance with different properties.
Important Notes:
* Chemical reactions are not always obvious: Sometimes, the changes are subtle, like the formation of a gas or a color change.
* Physical changes: Physical changes, like dissolving salt in water, do not result in the formation of new substances. The salt molecules simply separate and disperse, but their chemical structure remains unchanged.
* Chemical equations: Scientists use chemical equations to represent chemical reactions and show the reactants (starting substances) and products (new substances) involved.
Let me know if you'd like to explore specific examples or learn more about the types of chemical reactions!
