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Chemical Reactions

Chemical Reactions. Topic 7. Chemical Reaction happen all around us – even inside of us!. Chemical Reaction about t o take p lace…. Chemical Reactions. Chemical Reactions (  must know!) Two or more substances undergo a reorganization of atoms to form other substances.

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Chemical Reactions

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  1. Chemical Reactions Topic 7

  2. Chemical Reaction happen all around us – even inside of us! Chemical Reaction about to take place…

  3. Chemical Reactions • Chemical Reactions (must know!) • Two or more substances undergo a reorganization of atoms to form other substances. • Reactants (must know!) • The substances that go into a chemical reaction • Products (must know!) • The substances that are produced from a chemical reaction Reactant + Reactant  Products

  4. Give it a try!

  5. Chemical Reactions • When iodine is placed on a potato - a chemical reaction occurs and a blue-black colour is left. • Colour change indicates a chemical reaction • When two solutions are put together – they may form a precipitate (solid) • A precipitate and/or gas forming indicates a chemical reaction • Example: Silver Nitrate with Sodium Hydroxide • Click here  http://www.youtube.com/watch?v=SuoN0hQPeMw

  6. Chemical Reactions • When charcoal is burned, a chemical reaction occurs. • Heat and light production indicates a chemical reaction • When food spoils, its odour may change. • Odour change can indicate a chemical reaction

  7. Writing out Chemical Reactions • Writing out word equations • Writing out chemical equations

  8. Baking Soda and Vinegar! • We know Baking soda and vinegar go through a chemical reaction. • Word Equation Baking soda + Vinegar  Sodium acetate + water + carbon dioxide • Chemical Equation

  9. Try it out Situation: Burning Methane Word Equation Methane + Oxygen  Carbon Dioxide + Water Chemical Equation CH4(g) + O2(g) CO2(g) + H20(g)

  10. Energy in Chemical Bonds Energy is stored in chemical bonds To break bonds – energy is required To form bonds – energy is released

  11. Exothermic and Endothermic Even though many reactions take and release energy, we look at whether it takes more or loses more. Exothermic – Heatexits the chemical reaction Endothermic – Heatenters the chemical reaction

  12. Example • Burning gas in the car • Word equation • Propane + oxygen  carbon dioxide + water • Chemical equation • C3H8(g) + O2(g)  CO2(g) + H2O(g) + energy (heat!) • Even though you need to put a little energy in to start the chemical reaction, the heat produced is enough to keep the reaction going and more.

  13. Do You Recognize This Reaction? Photosynthesis is a chemical reaction. Is it exothermic or endothermic?

  14. Do You Recognize This Reaction? • Endothermic: • Why? Energy ENters the reaction • When you eat sugars and starches, you are eating molecules formed by endothermic reactions. Your cells break down these molecules in an exothermic process that supplies the body with energy. This exothermic process is called cellular respiration.

  15. Hot and Cold Packs Both hot and cold packs go through chemical reactions Which goes through an endothermic reaction? Which goes through an exothermic reaction?

  16. Hot and Cold Packs Both hot and cold packs go through chemical reactions Which goes through an endothermic reaction? Cold Packs Which goes through an exothermic reaction? Hot packs

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