* Fixed ratio: The elements in a compound always combine in a fixed, definite ratio. For example, water (H₂O) always has two hydrogen atoms for every one oxygen atom.
* New properties: Compounds have properties that are different from the elements that make them up. For example, sodium (Na) is a soft, silvery metal, and chlorine (Cl) is a poisonous gas, but their compound, sodium chloride (NaCl), is table salt.
* Chemical change: Forming a compound involves a chemical change, meaning new substances are created with different properties.
* Can be broken down: Compounds can be broken down into their constituent elements through chemical processes.
Here are some examples of compounds:
* Water (H₂O): Made of hydrogen and oxygen.
* Carbon dioxide (CO₂): Made of carbon and oxygen.
* Table salt (NaCl): Made of sodium and chlorine.
* Sugar (C₁₂H₂₂O₁₁): Made of carbon, hydrogen, and oxygen.
* Ethanol (C₂H₅OH): Made of carbon, hydrogen, and oxygen.
Key takeaway: A compound is a unique substance created by the chemical combination of two or more different elements in a fixed ratio, resulting in new properties and the ability to be broken down into its constituent elements.
