Elements Compounds and Mixtures

Elements, Compounds and Mixtures Content Elements Classifying Elements Properties Metal Metalloids Non-metals Appearance Shiny (lustrous) Shiny (lustrous) Dull (non-lustrous) Physical State in r.t.p Mostly Solids (Except for Mercury) Solids Gases, Volatile liquids or solids Melting and Boiling Points Mostly high (Except for Alkali Metals and Mercury) High Low (Except for Carbon and Silicon0 Ductility and Malleability - Ductile (Can be easily drawn to words) - Malleable (Can be hammered into different shapes without breaking) - Sonorous (Makes a ringing sound when struck) - Brittle (easily broken when hammered) - Brittle if solid Heat Conductivity Good Moderate Poor (Except Diamond and Graphite) Electrical Conductivity Good Moderate Poor (Except Graphite) Composition of Compounds - Made up of molecules or ions (electrically charged particles) - Ions particularly carries either carry a positive or negative charge Mixtures vs Compounds Property Mixtures Compounds Separation The components of a mixture can be separated by physical processes A compound can only be broken down into its elements or into simpler compounds by chemical processes. Properties The chemical properties of a mixture are the same as those of its components The physical and chemical properties of a compound are different from its constituent elements Energy Changes No chemical reaction takes place when a mixture is formed; usually there is little or no energy change A chemical reaction takes place when a compound is formed; Usually is an energy change, being either exothermic (heat is released) or endothermic (heat is taken in) Composition The components of a mixture can be mixed in any proportion The elements in a compound are always combined in a fixed proportion

Test yourself 1. Define i. Elements ii. Compounds iii. Mixtures iv. Monoatomic atoms v. Diatomic molecules vi. Polyatomic molecules 2. What are the differences between Compounds and Mixtures? Glossary of Terms Element Defined as a pure substance that cannot be broken down into two or more simpler substances by chemical Compound Defined as a pure containing two or more elements that are chemically combined in a fixed ratio Mixture Defined as two or more substances that are not chemically combined together. Diatomic molecules Formed by the combination of two atoms Polyatomic molecules Formed by the combination of three or more atoms Atoms Defined as the smallest particles of an element that have the chemical properties of that element Molecules Defined is a group of two or more atoms that are chemically combined together