CIE IGCSE Chemistry

Revision Notes

3.1.2 Bonding: the Structure of Matter

Types of Substance & Properties

Elements, compounds and mixtures

  • All substances can be classified into one of these three types

Element

  • A substance made of atoms that all contain the same number of protons (one type of atom) and cannot be split into anything simpler
  • There is a limited number of elements and all elements are found on the Periodic Table
  • Eg hydrogen, carbon, nitrogen

Compound

  • A pure substance made up of two or more elements chemically combined
  • There is an unlimited number of compounds
  • Compounds cannot be separated into their elements by physical means
  • Eg copper (II) sulphate (CuSO4), calcium carbonate (CaCO3), carbon dioxide (CO2)

Mixture

  • A combination of two or more substances (elements and/or compounds) that are not chemically combined
  • Mixtures can be separated by physical methods such as filtration or evaporation
  • Eg sand and water, oil and water, sulphur powder and iron filings

 

Elements, compounds & mixtures, IGCSE & GCSE Chemistry revision notesParticle diagram showing elements, compounds and mixtures 

 

Metals and nonmetals

  • The Periodic Table contains over 100 different elements
  • They can be divided into two broad types: metals and nonmetals
  • Most of the elements are metals and a small number of elements display properties of both types. These elements are called metalloids or semimetals

 

Metals, non-metals & metalloids in Periodic Table, IGCSE & GCSE Chemistry revision notesThe metallic character diminishes moving left to right across the Periodic Table

  

Properties of metals

  • Conduct heat and electricity
  • Are malleable and ductile (can be hammered and pulled into different shapes)
  • Tend to be lustrous (shiny)
  • Have high density and usually have high melting points
  • Form positive ions through electron loss
  • Form basic oxides 

Properties of nonmetals

  • Do not conduct heat and electricity
  • Are brittle and delicate when solid and easily break up
  • Tend to be dull and nonreflective
  • Have low density and low melting points (many are gases at room temperature)
  • Form negative ions through electron gain (except for hydrogen)
  • Form acidic oxides

Describing Alloys

  • Alloys are mixtures of metals, where the metals are mixed together but are not chemically combined
  • They can be made from metals mixed with nonmetals such as carbon
  • Alloys often have properties that can be very different to the metals they contain, for example they can have more strength, hardness or resistance to corrosion or extreme temperatures
  • Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms
  • This makes it more difficult for the layers to slide over each other, so they are usually much harder than the pure metal
  • Brass is a common example of an alloy which contains 70% copper and 30% zinc

 

Structure of alloy, IGCSE & GCSE Chemistry revision notesParticle diagram showing a mixture of elements in an alloy

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.
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