Mixtures and Dissolving

Mixtures

A mixture is made up of two or more substances that are not chemically bonded together, so the substances can easily be separated from each other. In a mixture, each substance keeps its own properties.

  • An example of a mixture is sand in water

Graphic of a blue flask containing a mixture. The bottom of the flask has a layer of sand, above which is a layer of clear water. The image is labelled 'Mixture' at the top and 'Water + Sand' at the bottom.

Water and sand are not joined together, so we can separate the mixture through filtering, yielding separated water and sand. This is because they are two separate substances.

Dissolving

Mixtures can be made in many ways, one of which is through dissolving. An example of this is when salt is stirred into water, the salt dissolves in the water.

Diagram illustrating the dissolving of salt in water. On the left, there's a glass beaker filled with water, and salt (NaCl) is being added. The right side zooms in to show a microscopic view of the solution, highlighting water molecules (H2O) and separated sodium (Na+) and chloride (Cl-) ions from the salt.

A solution is formed when a solute dissolves in a solvent.

Remember:

  • The substance that dissolves is the solute
  • The substance that the solute dissolves in is called the solvent

This means that in a salt solution, salt is the solute and water is the solvent. The solute and solvent are mixed completely. The techniques to separate the contents of mixtures include filtration, evaporation, distillation and chromatography.

Comparing Properties of Mixtures and Compounds

MixturesCompounds
DefinitionA mixture is a combination of two or more substances that are not chemically bonded togetherA compound contains atoms of different elements that are chemically bonded together in a fixed ratio
Chemically joined or notThe substances it contains are not chemically joined togetherThe elements it contains are chemically joined together
Ability to separateCan easily separate each substance from the mixtureCan only separate each element in a compound using chemical reactions
PropertiesEach substance in the mixture keeps its own propertiesEach element in the compound has different properties to the compound formed
CompositionMixtures contain different elements and compounds – The amount of each substance can varyCompounds contain different elements in a fixed ratio – The amount of each element in a compound does not vary, as the elements are chemically combined
ExamplesSalt water (a mixture of salt and water)

Air (a mixture of gases, including oxygen, nitrogen, and carbon dioxide
Water (made up of two hydrogen atoms and one oxygen atom, chemically bonded together)

Carbon dioxide (made up of one carbon atom and two oxygen atoms, chemically bonded together)

Diagram contrasting mixtures and compounds. On the left, a flask labelled 'Mixtures' shows particles of one substance mingling with particles of a different substance. This leads to 'Types of mixture' with three examples below: 'Salt Water' where the solute dissolves completely, 'Milk' with small particles, and 'Silt in Water' showcasing larger particles. On the right, a flask labelled 'Compounds' illustrates a chemical bond between atoms of different elements, leading to an example below of 'Water'.

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