* Chemical reactions involve the breaking and forming of chemical bonds between atoms. This results in the creation of new substances with different properties.
Examples of actions that form different chemical substances:
* Burning wood: Wood (cellulose) reacts with oxygen to produce ash, carbon dioxide, and water.
* Baking a cake: Flour, sugar, eggs, and other ingredients react with heat and each other, changing their chemical composition to form a cake.
* Rusting of iron: Iron reacts with oxygen and water to form iron oxide (rust), which has a different color and texture than iron.
* Digesting food: Enzymes in your body break down the complex molecules in food into simpler ones your body can absorb.
* Photosynthesis in plants: Plants use sunlight, carbon dioxide, and water to produce glucose (sugar) and oxygen.
Actions that don't form a different chemical substance:
* Mixing salt and pepper: You are simply combining two substances, not changing their chemical composition.
* Freezing water: Water changes its physical state from liquid to solid (ice) but its chemical composition remains the same (H₂O).
Key takeaway: A chemical reaction is needed to form a new chemical substance.
