Definition Of Pure Substances

Definition Of Pure Substances

A pure substance or chemical substance is a material that has constant composition (is homogeneous) and has consistent properties throughout the sample. Here are examples of pure substances

More About Pure Substances

  • A pure substance is any single type of material
  • A substance can be anything. It doesn't have to consist of a single element or type of molecule
  • Pure hydrogen is a pure substance. So is pure honey, even though it consists of many different types of molecules
  • If some oxygen is added to the hydrogen, the resulting gas is neither pure hydrogen nor pure oxygen
  • If corn syrup is added to the honey, we no longer have pure honey
  • A pure substance is considered to be a material that consists of one type of "building block" of matter
  • Both elements and compounds can be pure substances, homogenous mixtures are not considered to be pure substances
  • A substance cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds
  • A chemical substance can be solid, liquid, gas, or plasma
  • Chemical substances are often called 'pure' to set them apart from mixtures. A common example of a chemical substance is pure water; it has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory
  • Examples of pure substances include tin, sulfur, diamond, water, pure sugar (sucrose), table salt (sodium chloride) and baking soda (sodium bicarbonate)
  • Tin, sulfur and diamond are examples of pure substances which are chemical elements. All elements are pure substances
  • Water, sugar, salt and baking soda are pure substances which are chemical compounds. Chemical compounds also are pure substances
  • Depending on which substances we talk about, homogenous mixtures may be considered examples of pure substances. Examples of homogenous mixtures include vegetable oil, honey and air
  • In homogenous mixtures are not pure substances. Examples of materials which are not pure substances include gravel, your computer and a tree
  • We can use melting and boiling points and chromatography to test for pure substances.
  • Pure substances have a sharply defined (one temperature) melting or boiling point.
  • If a substance is pure then chromatography will only produce one substance at the end of the process

Question:

Methane, carbon monoxide, carbon dioxide, pure water and table salt are examples of _____.

A) Solutions
B) Compounds
C) Pure substances
D) B and C

Answer: D

 
 

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