The word 'pure' is used in chemistry in a different way from its everyday meaning. For example, shops sell cartons labelled as 'pure' orange juice. The label means that the contents are just orange juice, with no other substances added. However, the juice is not pure in the chemical sense because it contains different substances mixed together.
In chemistry:. Hydrogen and oxygen are both gases. Together, as a mixture, hydrogen and oxygen can react and form water. Water is a compound of hydrogen and oxygen. There are important differences between the properties of a mixture and a compound. In this table, the column 'Mixture' refers to the gasses hydrogen and oxygen, and the column named 'Compound' refers to water. Pure substances have a sharp melting point but mixtures melt over a range of temperatures.
Physical properties. Physical properties of pure substances are definite and constant. Mixtures have varying physical properties. Chemical properties. Chemical properties of pure substances are constant and definite too.
Mixtures have variable or indefinite chemical properties. Pure substances are, of course, pure. Mixtures are impure substances. It is not possible to separate pure substances.
It is possible to separate mixtures by evaporation, magnetic separation, etc. Gold, oxygen, iron, water. Oil and water, sand and soil, sugar solution. Property Pure Substance Mixture Definition The substances composed of only one particular matter are pure.
Categories Based on their composition, pure substances get classified into elements and compounds. Physical properties Physical properties of pure substances are definite and constant. Chemical properties Chemical properties of pure substances are constant and definite too. Elements are always pure substances, while compounds are chemical combinations of two or more elements and can also be pure. In the real world, substances such as elements and compounds are rarely pure because they are usually contaminated by their containers, their surroundings or their production.
In theory, pure means without detectable impurities,. It is usually possible to purify elements and compounds to that standard, although it often takes a great deal of effort. Compounds are made up of more than one pure substance, and they differ from mixtures in that it is impossible to separate them without a chemical reaction. Mixtures can be separated by physical processes, but these will not separate compounds.
If an element or compound exists in two states simultaneously, it can be a pure substance and a mixture at the same time. For example, pure water with pure crushed ice in it is still a pure substance, but it is also a mixture of two states of the pure substance. As a mixture, the ice can be separated from the water with physical means such as scooping out the ice fragments. Mixtures contain more than one type of atom or molecule and can be separated by using physical methods.
In homogeneous mixtures, the mixture particles are so fine that the mixture looks like it is made up of the same material throughout. For heterogeneous mixtures, the particles are detectable, and the properties of the mixture differ depending on what part of the mixture is examined. Solutions are typical homogeneous mixtures. For example, a solution of salt in water is a homogeneous mixture because the water and salt can be separated by distillation, producing pure water and crystalline salt.
Air is a mixture made up mainly of nitrogen and oxygen. The gases can be separated by cooling and liquefying the air and then boiling off nitrogen, which has a lower boiling point, and then oxygen, which boils at a higher temperature than nitrogen.
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