# Elements, Compounds and Mixtures

– Elements are the basic ‘building blocks” of all matter, which cannot be broken down into simpler substances by any physical and chemical methods.

– Atoms are the smallest possible unit of an element.

– Compounds are substances which consist of at least two or more elements chemically combined together.

– Molecules are the smallest possible unit of a compound and consist of at least two or more atoms chemically combined. Molecules may be comprised of atoms from the same element (eg. $Cl_{2}$) or atoms of different elements (ie. compound eg. $H_{2}O$).

– Mixtures are a combination of at least two or more atoms or molecules not chemically combined together.

– Some differences between compounds and mixtures are shown in the table below:

Compounds Mixtures
Pure substances, with two or more elements chemically joined together (a chemical reaction takes place when a compound is formed)  Not pure substances; where two or more elements and/or compounds are mixed together (not chemically joined together. A chemical reaction does not take place)
Have a fixed composition eg. water is always made up of 2 hydrogen and 1 oxygen atoms  Do not have a fixed composition
Cannot be separated into their components using physical methods  Can be separated into their components with physical methods like filtration, distillation
Have fixed melting and boiling points  Do not have fixed melting and boiling points
Have different chemical properties from their components  Have the properties of their components
Energy (may be in the form of heat or light) may be given out during their formation  Energy is usually not given out or taken in during mixing
Some examples include: water, carbon dioxide  Some examples include: air, salt water, soil

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### 1 thought on “Elements, Compounds and Mixtures”

1. thanks this is really helping my education

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