pure substances & mixures
A pure substance is a substance that is made up of only one type of particle. It has a definite composition and distinct properties. Pure substances can be further classified into elements and compounds.
An element is a pure substance that consists of only one type of atom. It cannot be broken down into simpler substances by chemical means. Examples of elements include oxygen, carbon, and gold.
A compound is a pure substance that is composed of two or more different types of atoms chemically combined in a fixed ratio. Compounds can be broken down into simpler substances by chemical reactions. Examples of compounds include water (H2O) and carbon dioxide (CO2).
On the other hand, a mixture is a combination of two or more substances that are not chemically combined. The substances in a mixture can be physically separated using various methods like filtration, evaporation, or chromatography. Mixtures can be classified into homogeneous mixtures and heterogeneous mixtures.
A homogeneous mixture, also known as a solution, has a uniform composition throughout and the individual components are not easily distinguished. Examples of homogeneous mixtures include saltwater, air, and stainless steel.
A heterogeneous mixture, on the other hand, does not have a uniform composition and the individual components are easily distinguishable. Examples of heterogeneous mixtures include salad dressing, soil, and granite.
In summary, pure substances are substances that are made up of only one type of particle, either an element or a compound, while mixtures are combinations of two or more substances that are not chemically combined.