Science Nine Hantsport School P. Warren Chemical Changes Science Nine Hantsport School P. Warren

Pure Substances when combined, may undergo a physical or a chemical change

Physical Change A change in matter in which no new type of matter is produced. Examples: Freezing --Cutting into pieces Melting --Ploughing a field Boiling --Moulding a Sculpture

Same Molecular Structure on both sides Physical Change Water (Ice) Water (Liquid) Same Molecular Structure on both sides

Chemical Change One or more new substances are formed in which these new substances have properties different from those of the starting materials Ex. Rusting of Steel before rusting after rusting (hard and shiny) (soft and reddish brown)

Ethane + Hydrogen  Methane + Methane Chemical Change Ethane + Hydrogen  Methane + Methane

Clues Indicating Chemical Change New Colour Appears Heat or Light is Given Off Bubbles of Gas are Formed Solid Material Forms in a Liquid (Precipitate) The Change is Difficult to Reverse

Iron + Oxygen + Water  Rust Chemical Reactions A chemical change results from a chemical reaction which involves reactants and products. Iron + Oxygen + Water  Rust Reactants Product Plus Plus Produces

Examples of Chemical Changes Reactant Products Hydrogen Peroxide  water + oxygen Ethane + Hydrogen  Methane + Methane Reactant(s) are any substance(s) that is used up in a reaction Product(s) are any substances that is produced in a reaction Reactants Products

Writing Chemical Reactions Reactant + Reactant  Product + Product Example: Copper (II) Sulphate reacts with iron to produce Iron (II) Sulphate and Copper Copper (II) Sulphate + Iron  Iron (II) Sulphate + Copper Reactants Products

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