What are the differences between substances and mixtures?
A substance is a collection of like particles - all one element or compound. A mixture is multiple substances mingled together.
Substances are one type of particle.
Gold (Au, an element) and Carbon Dioxide (CO2, a compound) are examples of substances.
Mixtures consist of multiple substances and can be homogeneous (evenly distributed) or heterogeneous (unevenly mixed particles)
Saltwater (NaCl dissolved in H2O) is a mixture; it consists of two substances. Alloys of metals and mixtures of gases such as air are other examples of homogeneous mixtures. Soil and sand in water are examples of heterogeneous mixtures.