chemical reactions
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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. - PowerPoint PPT PresentationTRANSCRIPT
Chemical ReactionsTopic 7
Chemical Reaction happen all around us – even inside of us!
Chemical Reaction about to
take place…
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 reactionReactant + Reactant Products
Reaction #
Reactants Products Word Equation
1 Hydrogen Peroxide + Heat
Water + Oxygen
Hydrogen Peroxide + Heat Water + Oxygen
2 Silver + Oxygen Silver oxide Silver + Oygen Silver oxide
3 Sodium + Bromine Sodium bromide Sodium + Bromine Sodium bromide
GIVE IT A TRY!
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
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
Writing out Chemical Reactions1. Writing out word equations
2. Writing out chemical equations
Baking Soda and Vinegar! We know Baking soda and vinegar go
through a chemical reaction.
Word EquationBaking soda + Vinegar Sodium acetate + water + carbon dioxide
Chemical Equation
Try it out Situation: Burning Methane
Word EquationMethane + Oxygen Carbon Dioxide +
Water
Chemical EquationCH4(g) + O2(g) CO2(g) + H20(g)
Energy in Chemical Bonds Energy is stored in chemical bonds
To break bonds – energy is required
To form bonds – energy is released
Exothermic and Endothermic
Even though many reactions take and release energy, we look at whether it takes more or loses more.
Exothermic – Heat exits the chemical reaction
Endothermic – Heat enters the chemical reaction
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.
Do You Recognize This Reaction?
Photosynthesis is a chemical reaction.
Is it exothermic or endothermic?
Do You Recognize This Reaction?
Endothermic:Why? Energy ENters the reactionWhen 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.
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?
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