Sorting Matter Into Four Groups

By the end of this lesson, you will be able to model and explain how matter is classified as an element, a compound, a homogeneous mixture, or a heterogeneous mixture.

Everything around you is matter, which is anything that has mass and takes up space. Scientists sort matter first by asking one question: is it a pure substance, made of only one kind of particle, or a mixture, made of two or more substances that are physically blended but not chemically joined? Pure substances split into elements and compounds, and mixtures split into homogeneous and heterogeneous.

An element is a pure substance made of only one kind of atom, like the copper in a penny or the aluminum in foil. If you model an element with circles, you would draw all identical circles. A compound is a pure substance made of two or more different atoms chemically bonded together, like water or table salt. In a model, a compound looks like matching pairs or groups, such as one big circle stuck to two small circles, repeated over and over.

Think about a plate of nachos at a Friday night football game. The cheese sauce spread evenly over the chips looks the same everywhere you sample it, so it is a homogeneous mixture, sometimes called a solution. The whole plate, with chips, beans, jalapeños, and cheese in different spots, is a heterogeneous mixture, because you can see the different parts and each bite is different. A drawing of a homogeneous mixture shows two kinds of particles spread evenly; a heterogeneous mixture shows clumps.

Remember that mixtures can be separated by physical means, like picking jalapeños off your chips, while compounds can only be separated by chemical changes.

Try it: if you drew a model showing evenly scattered circles and squares that are never bonded together, which of the four groups would you be modeling?