Elements, Compounds and Mixtures

Element

A substance which cannot be broken down into two or more simpler substances by chemical methods

Compound

A substance made up of two or more elements that are chemically combined together

Mixture

Two or more substances that are mixed, but not chemically combined

Saturated solution

A solution in which the maximum mass of solute has dissolved in a fixed amount of solvent at a given temperature

Solubility curve

A graph that shows the maximum mass of solute that can dissolved in 100g of solvent at a given temperature

Molecule

• A group of two or more atoms that are chemically combined together

• Molecules do not need to be made up of the same type of atoms

Pure substances

Made up of only one element or compound

Impure substances

Made up of two or more substances that are mixed but not chemically combined

Properties of mixtures

• A mixture has the properties of the substances it is made up of

• The substances that make up a mixture are not in a fixed proportion by mass

• A mixture can be separated by physical methods

Properties of compounds

• A compound has different properties from that of its constituent elements

• The elements that make up a compound are always in a fixed proportion by mass'

• A compound cannot be broken down by physical methods

Test for pure liquid

Heat the liquid sample, if it boils at a fixed temperature, it is pure

Test for pure solid

Heat the solid sample, if it melts at a fixed temperature, it is purefs

Test for impure liquid

Heat the liquid sample, if it boils over a range of temperatures, it is impure

Test for impure solid

Heat the solid sample, if it melts over a range of temperatures, it is impure