Pure Substances & Mixtures Flashcards

All 5 cards in this deck

In chemistry, what is a pure substance?

A single element or compound, not mixed with any other substance.
e.g. pure water contains only water molecules

How does the everyday use of 'pure' differ from the chemical meaning?

Everyday 'pure' means natural or with nothing harmful added; chemically it means only one substance is present.

True or false? Bottled drinking water labelled 'pure' is a pure substance in the chemical sense.

False. It contains dissolved solids such as calcium ions, so it is a mixture (impure).

How do the melting points of a pure substance and a mixture differ?

A pure substance melts at one sharp temperature; a mixture melts over a range of temperatures.

True or false? Air is a mixture but carbon dioxide is not.

True. Air is a mixture of substances, whereas carbon dioxide is a compound.