* Law of Definite Composition: This law states that a chemical compound always contains the same elements in the same proportions by mass, regardless of its source or how it was prepared.
* Mixtures: Mixtures are formed when two or more substances are physically combined. The substances in a mixture retain their individual properties and can be separated by physical means. Importantly, the proportions of the components in a mixture can vary.
Examples:
* Salt water: You can dissolve a teaspoon of salt in a cup of water or a tablespoon of salt in a cup of water. Both mixtures are salt water, but the ratio of salt to water differs.
* Air: Air is a mixture of gases like nitrogen, oxygen, and carbon dioxide. The proportions of these gases can vary slightly depending on location and altitude.
Key Takeaway: The law of definite composition applies to chemical compounds, which are formed by the chemical combination of elements. Mixtures, on the other hand, are simply physical combinations of substances that do not undergo chemical change.
