1. Rearrangement of Atoms
* Bonds Break: The chemical bonds holding atoms together in the reactants are broken. This requires energy input.
* Bonds Form: New bonds are formed between atoms, creating the products. This process releases energy.
2. Energy Changes
* Exothermic Reactions: Release more energy than they absorb, resulting in a net release of energy to the surroundings. The products have lower energy than the reactants.
* Endothermic Reactions: Absorb more energy than they release, resulting in a net absorption of energy from the surroundings. The products have higher energy than the reactants.
3. Conservation of Mass
* The Law of Conservation of Mass: The total mass of the reactants before the reaction must equal the total mass of the products after the reaction. Atoms are neither created nor destroyed, but simply rearranged.
4. Changes in Chemical Properties
* New Substances: The products have different chemical properties than the reactants. They are fundamentally different substances.
5. Activation Energy
* The Energy Barrier: Chemical reactions need a certain amount of energy (activation energy) to get started, even if they are exothermic. This energy helps break existing bonds and initiate the reaction.
Key Points to Remember:
* Not All Reactions are Visible: Many chemical reactions occur at the molecular level and are not obvious to our senses.
* Rates of Reaction Vary: Reactions happen at different speeds, influenced by factors like temperature, concentration, and the presence of catalysts.
* Reversibility: Some reactions can proceed in both directions, with reactants forming products and vice versa.
Let me know if you'd like a deeper dive into any specific aspect of chemical reactions!
