Pure Substances + Formulations

What is a pure substance in chemistry?

A substance containing only one element or one compound, with no other substances mixed in.

What is a mixture?

Two or more substances that are not chemically bonded together.

What is the difference between a pure substance and a mixture?

A pure substance contains one element or compound, whereas a mixture contains two or more substances.

What is meant by a pure substance in everyday language?

A substance with nothing added to it, which may differ from the scientific definition.

How can melting point be used to identify a pure substance?

A pure substance has a sharp, specific melting point.

How can boiling point be used to identify a pure substance?

A pure substance has a specific boiling point at a given pressure.

What happens to the melting point of a substance when impurities are present?

Impurities usually lower the melting point and broaden the melting range.

What happens to the boiling behaviour of a substance when impurities are present?

Impurities often cause boiling over a range of temperatures rather than at one sharp temperature.

Why can melting point help identify an unknown substance?

Its measured melting point can be compared with known reference values.

Why can boiling point help identify an unknown substance?

Its boiling point can be compared with reference data.

What is a formulation?

A mixture designed as a useful product, with substances in carefully measured quantities.

Why are formulations produced?

To obtain a product with specific properties for a particular purpose.

Why are the quantities of substances carefully controlled in formulations?

To ensure the product has consistent and suitable properties.

What are examples of formulations?

Fuels, cleaning agents, paints, medicines, fertilisers, foods and alloys.

Why are medicines examples of formulations?

They contain carefully measured ingredients to provide the required properties and effects.

Why are paints examples of formulations?

They contain substances chosen to give colour, coverage, durability and suitable consistency.

Why are fertilisers examples of formulations?

They contain controlled proportions of nutrients required for plant growth.

What is the difference between a formulation and a pure substance?

A formulation is a purpose-designed mixture, while a pure substance contains only one element or compound.

Does a formulation have to contain chemically bonded substances?

No, its components form a mixture.

Why is chemical analysis important?

It allows substances to be identified, separated and tested for purity.