Pure substances & mixtures

Define pure substances And mxitures

A pure substance is a matter that has a fixed (constant) composition and unique property e.g oxygen gas is an example of pure substances as its only made up up of oxygen

• Fixed boiling points

• Cannot be separated into simpler substances by physical means

Mixture is matter that contains at least two physically combined compounds e.g air is an example of a mixture as it is made up of oxygen gas, nitrogen gas and carbon dioxide gas which are all pure substances.

• Variable composition

• separated into their components by physical methods such as filtration, distillation, or evaporation.

Describe the types of pure substances and provide examples.

Elements - Elements are pure elements (cannot be broken down). one atom

• Metals Gold

• Non metals oxygen

• Noble gases helium

Compounds - two or more elements chemically combine in fixed proportions. They can be broken down into simpler substances through chemical reactions.

• Water

• Carbon dioxide

• Sodium chloride

Describe the types of mixtures and provide examples.

Homogenous mixture, uniform composition throughout → different components are evenly distributed and cannot be easily distinguished from one another

• Saltwater

• Air

Heterogeneous mixture Non-uniform composition → different components can be seen and separated individual substances retain their properties ( see and take away)

• Salad

• Sand and iron fillings

• Oil and water