* Energy Input (Endothermic Reactions): Some reactions require energy to proceed. This energy is absorbed from the surroundings, causing the temperature to drop. Examples include melting ice or photosynthesis.
* Energy Output (Exothermic Reactions): Other reactions release energy into the surroundings, causing the temperature to rise. Examples include burning wood or a combustion reaction.
In addition to energy, chemical reactions also involve the transfer of:
* Electrons: This is fundamental to most chemical reactions. Electrons are transferred between atoms, changing their chemical bonds and forming new substances. This can happen through:
* Ionic bonding: Complete transfer of electrons between atoms, creating ions with opposite charges.
* Covalent bonding: Sharing of electrons between atoms, creating molecules.
* Atoms: While not always visible, some reactions involve the rearrangement of atoms within molecules. This can lead to the formation of new compounds.
Key Takeaway: All chemical reactions involve the transfer of energy, and often the transfer of electrons and/or atoms. The type and amount of transfer dictate the reaction's characteristics.
