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Characteristics of Substances Elements, compounds, mixtures Atoms Smallest piece Elements Red block Blue block Each type of Atom is called an Element LEGO Different colours ,sizes and shapes WORLD Different properties • Elements are substances made up of only one type of atom. • Example: Molecules A molecule is made up of two or more atoms chemically combined. O H H Water (H2O) Chemical Reaction Element or Molecules combining together = > Chemical Reaction O + O H H H H Water (H2O) Aristotle's Elements Earth Air Fire Water What is an Element ? • Everything in the Universe is made from Elements • There are over 100 elements • The most common element in the Universe is Hydrogen • The Term “Element” was introduced by an Irish scientist Robert Boyle – – “Simple Substance” Element An Element is a substance that cannot be split up into simpler substances by chemical means. Common Elements Oxygen – Most abundant Element in Earths Crust What is this ? Element Oxygen Carbon Hydrogen Nitrogen Calcium Phosphorus Potassium Sulfur Sodium Magnesium Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine, Iodine, Manganese, Cobalt, Iron Percentage 65% 18% 10% 3% 1.5% 1.0% 0.35% 0.25% 0.15% 0.05% 0.70% Lithium, Strontium, Aluminium, Silicon, Lead, Vanadium, Arsenic, Bromine Trace amounts Periodic Table of Elements Symbols • Each Element is given a unique Symbol – First letter of its name (H, C, O) – First two letters of its name (Si, Ne, Li) – Taken from its Latin name (Pb, Fe, Au) Metals METAL Copper Zinc Aluminium Iron Silver Gold SYMBOL Cu Zn Al Fe Ag Au Non Metals NON METAL Carbon Oxygen Sulphur Hydrogen Nitrogen SYMBOL C O S H N Atom An Atom is the smallest particle of an Element that still retains the properties of that element. What’s inside the atom? Compounds A Compound is a substance that is made up of two ore more different elements combined chemically together. Compounds H O C H H H H Water (H2O) H Methane (CH4) O C Carbon Dioxide (CO2) O Compound ? O O Oxygen (O2) H H Hydrogen (H2) • When a compound is formed during a chemical reaction its properties differ from those of the elements from which it is made Mixtures • A mixture consists of two or more different substances mingled together but not chemically combined. • Examples: Sea – water and salt Air – nitrogen, oxygen … Soil – sand, clay, humus … Mixture vs Compound Mixture The amounts of the substances in the mixture can vary. Compound The elements in a compound are always present in the same fixed proportion. A mixture contains two or more A compound is a single substances 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 Heat is usually given out or changes when a mixture is made taken in when a compound is formed. It is usually easy to separate the It is usually difficult to separate components of a mixture. the components of a compound.