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Chemical reactions

Chemical reactions. Chemical reactions. Chemical reactions are processes in which substances change into other substances. You know a chemical reaction takes place if one or more of these occur:

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Chemical reactions

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  1. Chemicalreactions

  2. Chemicalreactions Chemicalreactions are processes in which substances change into other substances. You know a chemical reaction takes place if one or more of these occur: Color changes - Different combinations of molecules reflect light differently. A color change indicates a change in molecules. Heat content changes - In all chemical reactions, the heat content of the reactants and the heat content of the products is never the same. Sometimes the difference is great and can be easily detected. At other times, the difference is slight and more difficult to detect. Gas produced - Whenever a gaseous product forms in a liquid solution, bubbles can be seen. A colorless gas produced in a reaction of solids is much harder to detect. Precipitate forms - Precipitates are insoluble products formed by a reaction taking place in a liquid solution. This insoluble product will eventually settle to the bottom, but might immediately appear by turning the clear solution cloudy.

  3. Types of chemicalreactions 1. DecompositionReactions: A compoundbreaksintoparts. compound → element + element 2H2O → 2H2 + O2 Somedecompositioncomplicationswithheat: Someacids, whenheated, decomposeintoanacidic oxide and H2O. H2SO3 → SO2 + H2O Metallichydroxides, whenheated, decomposeinto a metallic oxide and H2O. Ca(OH)2 → CaO + H2O Metallic carbonates, whenheated, decomposeinto a metallic oxide and CO2. Li2CO3 → Li2O + CO2 Metallicchlorates, whenheated, decomposeintometallicchlorides and O2. 2KClO3 → 2KCl + 3O2

  4. Types of chemicalreactions 2. Synthesis Reactions: Elements or compounds are joined together. element + element → compound 2H2 + O2 → 2H2O compound + compound → compound 6CO2 + 6H2O → C6H12O6 + 6O2

  5. Types of chemicalreactions 3. Single Displacement Reactions: A single element replaces an element in a compound. element + compound → element + compound Zn + 2HCl → H2 + ZnCl2

  6. Types of chemicalreactions 4. Double Displacement Reactions: An element from each of two compounds switch places. compound + compound → compound + compound H2SO4 + 2NaOH → Na2SO4 + 2H2O

  7. Types of chemicalreactions 5. CombustionReactions: A hydrocarbon (a compoundcontainingonlycarbon and hydrogen) combines withoxygen. Theproducts of combustion are alwayscarbondioxide and water. hydrocarbon + oxygen → carbondioxide + water CH4 + 2O2 → CO2 + 2H2O When metallic substances combine with oxygen, the result is an oxidation-reduction reaction (6). 4Fe + 3O2 → 2Fe2O3

  8. Combustionreaction of methane

  9. Types o chemicalreactions 7. Neutralization Reactions: Special types of double displacement reactions that involve the reaction between an acid and base to form a salt and water. acid + base → salt + water Heat is usually given off in neutralization reactions. A suspension of solid magnesium hydroxide in water is widely used as an antacid to neutralize excess stomach acid: Mg(OH)2 (s) + 2HCl (aq) → MgCl2 (aq) + 2H2O (l)

  10. Types of chemicalreactions 8. Precipitation Reactions: Aqueous reactions that involve the formation of a precipitate (solid). soluble compound + soluble compound → insoluble compound 2KI (aq) + Pb(NO3)2 (aq) → 2KNO3 (aq) + PbI2 (s) The physical state symbol (aq) says the reaction is taking place in a water solution. The physical state symbol (s) says the lead (II) iodide is a solid - therefore insoluble in the solution.

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