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Chemical reactions kathryn thumath 25/08/2019
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What is a chemical reaction?
In a chemical reaction a new substance is always formed. We can tell if a chemical reaction has taken place by the following changes: Colour change Energy change – heat, light, sound. Solid formed – precipitate Gas produced - efferervesence 25/08/2019
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Examples of chemical reactions
A plant growing Something burning Baking a cake Striking a match Oil forming 25/08/2019
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Key Words Atom - tiny particle.
Element – substance made of only one type of atom. Compound – 2 or more elements joined together. Mixture – substances mixed but not joined. Reactant – something that is used up in a reaction. Product – the new substance that is produced in a reaction 25/08/2019
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Separating Mixtures Examples Filtering
This separates a solid from a liquid. A soluble substance from an insoluble one e.g. sand and salty water. Distillation This will separate a mixture of liquids that have different boiling points. Chromatography This will separate the mixtures of ink in a pen. 25/08/2019
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Chemical Reactions In a chemical reaction the reactants combine to form a new substance - the product. Chemical equations This is a short hand what of writing down what has happened in a reaction. Example Reactant + Reactant Product Hydrogen + Oxygen Water These are examples of word equations. 25/08/2019
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Chemical Equations These are short hand ways of writing down what happens in a reaction . However here we put in the Chemical Symbols for the elements and the compounds. Example H2 + O2 H2O State Symbols These tell you state a substance is in at room temperature. S = solid, L = Liquid, G = Gas Aq. = in solution with water 25/08/2019
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