elements, compounds and mixtures. chapter 16. classification of substances elements molecules...
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Elements, Compounds and Mixtures.Chapter 16
Classification of SubstancesElementsMoleculesCompoundsMixtures.
ElementsElements are substances made up of only one type of atom.Example Hydrogen, Gold.
Periodic Table of Elements
Molecule A molecule is made up of two or more atoms chemically combined.
CompoundsCompounds are made up of two or more different types of atoms chemically combined.
Properties of CompoundsWhen a compound is formed during a chemical reaction its properties differ from those of the elements from which it is made.Example: Water is made from hydrogen and oxygen.Hydrogen flammable gasOxygen colourless gas.
Diagram of Salt, water, sucrose.
MixturesA mixture consists of two or more different substances mingled together but not chemically combined.Examples:Sea water and saltAir nitrogen, oxygen Soil sand, clay, humus
Compare mixtures and Compounds.
MixtureCompoundThe amounts of the substances in the mixture can vary.The elements in a compound are always present in the same fixed proportion.A mixture contains two or more substancesA compound is a single substance.The properties of a mixture are similar to those of the substances in a mixture.The properties of a compound are different to those of the elements which reacted to form it.There are practically no energy changes when a mixture is madeHeat is usually given out or taken in when a compound is formed.It is usually easy to separate the components of a mixture.It is usually difficult to separate the components of a compound.
iron particlesKey:strong bonds between iron particles one iron particleiron particles held together by strong bonds
iron particles iron particles are attracted to a magnetiron particles diagram
sulfur particlesKey:strong bonds between sulfur particles one sulfur particlesulfur particles held together by strong bonds
sulfur particlessulfur particles are not attracted to a magnetsulfur particles diagram
A mixture of iron and sulfur particlesstrong bonds between sulfur particles strong bonds between iron particlesWhats this?
A mixture of iron and sulfur particlesA magnet attracts the iron particles but not the sulfur particles.The mixture is separatedmixture diagram
one sulfur particle one iron particlestrong bonds between iron and sulfur particlesWhats this?A compound between iron and sulfur particles
strong bonds between iron and sulfur particlesA compound between iron and sulfur particlesThe magnet cannot separate iron and sulfur particles in a compoundcompound diagram
ReferencesSteve Lewis for the Royal Society of Chemistry
Photographs by Peter Hollamby