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Chemical Reactions

Chemical Reactions. Test on Friday April 19. Chemical Reaction. Chemical Reaction – a change in which one or more substances are converted into new substances Reactants – substances that react Products – substances that are produced Reactants  Products. Conservation of Mass.

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Chemical Reactions

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  1. Chemical Reactions Test on Friday April 19

  2. Chemical Reaction • Chemical Reaction – a change in which one or more substances are converted into new substances • Reactants – substances that react • Products – substances that are produced Reactants  Products

  3. Conservation of Mass • Total mass of reactants is always equal to the total mass of products – Antoine Lavoisier • Matter is not created or destroyed; it is conserved. • Law of Conservation of Mass 10 grams HgO = 0.7 grams O + 9.3 grams Hg

  4. Father of Modern Chemistry • Lavoisier is known as the Father of Modern Chemistry for this work along with the work he did on types of reactions • Wrote a book called “Elements of Chemistry” in 1790 • He developed the nomenclature we use today to describe chemical compounds and reactions.

  5. Chemical Equations • A way to describe a chemical reaction using chemical formulas and other symbols. •  produces or forms • + plus • (s) solid (l) liquid (g) gas (aq) aqueous

  6. Coefficients • Coefficients – the numbers in front of the chemical formulas that represent the number of units of each substance taking part in a reaction. • Must be whole numbers • Act like a multiplier and apply to the entire formula • Subscripts – small numbers that tell how many atoms a particular molecule has

  7. Sample Equations • 2Hg + Br2 → Hg2Br2 • Hg2Br2 + 2Cl2 → 2HgCl2 + Br2 • 2C4H10 + 13O2 → 8CO2 + 10H2O

  8. Balanced Chemical Equations • An equation is balanced if it has the same number of atoms on each side of the equation. • This is due to the Law of Conservation of Matter: Matter cannot be created or destroyed.

  9. Steps to Balancing • Write a chemical equation if you don’t already have one. • Remember Oxygen, Chlorine and Hydrogen are diatomic. • Count the atoms on each side. • Choose coefficients that multiply to balance the equation. • Recheck the numbers.

  10. Types of Reactions • There are 5 types of reactions: • Combustion • Synthesis • Decomposition • Single Displacement • Double Displacement

  11. Combustion Reactions • When a substance reacts with oxygen to produce energy in the form of heat and light (fire) • Only includes the elements: C, H, and O • Always produces CO2 and H2O CxHx + O2  CO2 + H2O

  12. Synthesis Reactions • Two or more substances (elements) combine to form one substance (molecule) • Easily found because there is only one product Element + Element  Molecule

  13. Decomposition Reaction • One substance (molecule) breaks down into multiple substances (elements) • Easily found because there is only one reactant. Molecule  Element + Element

  14. Single Displacement • An element reacts with a molecule. One of the elements in the molecule recombines with the original element. • The reactants and products are both one element and one molecule. A + BC  AC + B “unhappy breakup”

  15. Double Displacement • The positive ions switch places to form two new compounds. • The reactants and products are always two molecules. AD + BC  AC + BD “happy breakup”

  16. Activity Series • The Activity Series is a chart that tells which metals will replace other metals in a reaction.

  17. Vocabulary • Precipitate – insoluble compound that comes out of a solution • Oxidation – loss of electrons • Reduction – gain of electrons

  18. Chemical Reactions and Energy • All chemical reactions either absorb or release energy • Breaking bonds requires energy • Forming bonds releases energy • Energy can take the form of light, heat, sound, or electricity.

  19. Exergonic • Reactions that release energy are called Exergonic • When that energy is given off as heat its called Exothermic • You can feel the reaction get warmer.

  20. Endergonic • Reactions that absorb energy are called Endergonic. • When that energy is in the form of heat its called Endothermic. • You can feel the reaction get colder.

  21. Catalysts and Inhibitors • A catalyst is a substance that speeds up a reaction. • An inhibitor is a substance used to slow down a reaction or prevent it completely. • The catalyst and the inhibitor do not participate in the reaction. They remain unchanged after the reaction is over.

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