Which cannot be classified as a substance

A simple distillation apparatus for separating a mixture of substances, at least one of which is a liquid. The most volatile component boils first and is condensed back to a liquid in the water-cooled condenser, from which it flows into the receiving flask.

If a solution of salt and water is distilled, for example, the more volatile component, pure water, collects in the receiving flask, while the salt remains in the distillation flask. Mixtures of two or more liquids with different boiling points can be separated with a more complex distillation apparatus. One example is the refining of crude petroleum into a range of useful products: aviation fuel, gasoline, kerosene, diesel fuel, and lubricating oil in the approximate order of decreasing volatility.

Another example is the distillation of alcoholic spirits such as brandy or whiskey. This relatively simple procedure caused more than a few headaches for federal authorities in the s during the era of Prohibition, when illegal stills proliferated in remote regions of the United States!

Crystallization separates mixtures based on differences in solubility, a measure of how much solid substance remains dissolved in a given amount of a specified liquid. Most substances are more soluble at higher temperatures, so a mixture of two or more substances can be dissolved at an elevated temperature and then allowed to cool slowly.

Alternatively, the liquid, called the solvent, may be allowed to evaporate. In either case, the least soluble of the dissolved substances, the one that is least likely to remain in solution, usually forms crystals first, and these crystals can be removed from the remaining solution by filtration. Most mixtures can be separated into pure substances, which may be either elements or compounds. An element , such as gray, metallic sodium, is a substance that cannot be broken down into simpler ones by chemical changes; a compound , such as white, crystalline sodium chloride, contains two or more elements and has chemical and physical properties that are usually different from those of the elements of which it is composed.

With only a few exceptions, a particular compound has the same elemental composition the same elements in the same proportions regardless of its source or history.

The chemical composition of a substance is altered in a process called a chemical change. The conversion of two or more elements, such as sodium and chlorine, to a chemical compound, sodium chloride, is an example of a chemical change, often called a chemical reaction.

Currently, about elements are known, but millions of chemical compounds have been prepared from these elements. The known elements are listed in the periodic table. In general, a reverse chemical process breaks down compounds into their elements.

For example, water a compound can be decomposed into hydrogen and oxygen both elements by a process called electrolysis. A similar technique is used on a vast scale to obtain pure aluminum, an element, from its ores, which are mixtures of compounds. Because a great deal of energy is required for electrolysis, the cost of electricity is by far the greatest expense incurred in manufacturing pure aluminum.

Thus recycling aluminum is both cost-effective and ecologically sound. Identify each substance as a compound, an element, a heterogeneous mixture, or a homogeneous mixture solution. Matter can be classified according to physical and chemical properties. Matter is anything that occupies space and has mass. The three states of matter are solid, liquid, and gas.

A physical change involves the conversion of a substance from one state of matter to another, without changing its chemical composition. Most matter consists of mixtures of pure substances, which can be homogeneous uniform in composition or heterogeneous different regions possess different compositions and properties. Pure substances can be either chemical compounds or elements. Compounds can be broken down into elements by chemical reactions, but elements cannot be separated into simpler substances by chemical means.

The properties of substances can be classified as either physical or chemical. Scientists can observe physical properties without changing the composition of the substance, whereas chemical properties describe the tendency of a substance to undergo chemical changes chemical reactions that change its chemical composition. Physical properties can be intensive or extensive. Any given spoonful of soup will contain varying amounts of the different vegetables and other components of the soup.

A phase is any part of a sample that has a uniform composition and properties. By definition, a pure substance or a homogeneous mixture consists of a single phase. A heterogeneous mixture consists of two or more phases.

When oil and water are combined, they do not mix evenly, but instead form two separate layers. Each of the layers is called a phase. Identify each substance as a compound, an element, a heterogeneous mixture, or a homogeneous mixture solution. A pure substance is a form of matter that has a constant composition and properties that are constant throughout the sample. Mixtures can be classified as homogeneous or heterogeneous. Compounds are substances that are made up of more than one type of atom.

Elements are the simplest substances made up of only one type of atom. This page was constructed from content via the following contributor s and edited topically or extensively by the LibreTexts development team to meet platform style, presentation, and quality:.

Chem1 Virtual Textbook. Learning Objectives Explain the difference between a pure substance and a mixture. Explain the difference between an element and a compound. Explain the difference between a homogeneous mixture and a heterogeneous mixture. Phase A phase is any part of a sample that has a uniform composition and properties. If it is pure, the substance is either an element or a compound. If a substance can be separated into its elements, it is a compound.

If a substance is not chemically pure, it is either a heterogeneous mixture or a homogeneous mixture. If its composition is uniform throughout, it is a homogeneous mixture.

Solution A Tea is a solution of compounds in water, so it is not chemically pure. This site is not fully supported in Internet Explorer 7 and earlier versions. Please upgrade your Internet Explorer to a newer version. Close Do not show this message again.

Close Find out more on how we use cookies. EU Privacy Disclaimer. This website uses cookies to ensure you get the best experience on our websites. Read More OK. Substance identification Why is it important to get it right? What is a substance? What is not a substance?