4. Elements, Compounds, and Mixtures

Question 1

Element v Compound v Mixture

Answer 1

An element is a substance made up of only one type of atom. Compounds are made up of more than one type of atom chemically bonded together. Examples include carbon dioxide (CO2), water (H2O) and methane (CH4), which are all made up of two or more types of atoms bonded together. A mixture is a group of different elements or compounds which are not chemically bonded together. Air is a mixture, as it is made up of nitrogen, oxygen, carbon dioxide and water vapour compounds.

Question 2

How do Mixtures differ from pure substances

Answer 2

Mixtures will melt and boil over a range of different temperatures, as each component of the mixture will change state at different temperatures.

Mixtures can be separated by filtration, distillation, crystallisation or chromatography. The technique used depends on the nature of substances which make up the mixture. A pure substance, any compound or element, can’t be separated into different atoms by physical methods. A chemical reaction must occur to separate a compound into its different atoms/elements.

Question 3

Diatomic Elements

Answer 3

A diatomic molecule is a molecule made up of two atoms.
Almost all diatomic molecules are gases when kept at ambient temperature.

diatomic elements are hydrogen (H), nitrogen (N), oxygen (O), fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). E.g Oxygen exists as O2.
Only Group VIII (8) elements truly exist as separate atoms.