1 / 24

Chapter 21 Chemical Equations Section 1 Chemical Change

Chapter 21 Chemical Equations Section 1 Chemical Change. What is a chemical reaction?. A. Describing chemical reactions. Chemical Reactions- change of one or more substances converted into new substances Reactants - substances that combine or change

trizzo
Download Presentation

Chapter 21 Chemical Equations Section 1 Chemical Change

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 21 Chemical EquationsSection 1 Chemical Change

  2. What is a chemical reaction?

  3. A. Describing chemical reactions • Chemical Reactions- change of one or more substances converted into new substances • Reactants - substances that combine or change • Products- new substances that are produced produce Reactants  Products

  4. B. Conservation of Mass • Conservation of Mass-a law which states that, in a chemical reaction, mass is not created or destroyed; it stays the same • Antione Lavoisier – Father of Modern Chemistry • Found mass of products equaled the mass of the reactants

  5. C. Writing Equations • Chemical equation - uses chemical formulas and symbols to describe a chemical reaction and the products it produces • Chemical formula - expresses the relationship between elements in the compounds and molecules they make up • Symbols used to show physical state of reactants; (s) solids (aq) aqueous (g) gas (l) liquid

  6. C. Writing Equations • Coefficients – whole numbers in front of the symbol, which represent the number of units of each substance in a reaction **Located before the symbols • Subscripts – small lowered numbers which represent the number of atoms in a molecule of a particular element *Located after and below the symbols • Nomenclature – way to name things scientifically

  7. Discussion Questions • What does the law of conservation of mass state? • What is the function of coefficients in a chemical equation?

  8. Answers • In a chemical reaction, matter is neither created nor destroyed. The total sum of the reactants must equal the sum of the product. • Chemist need to know how much of a reactant will produce a certain amount of product

  9. Describe 3 chemical reactions that you have observed (EX: burning marshmallow) • There are many things that let you know it’s a chemical reaction: color change, forming a precipitate, production of heat.

  10. Section 2Chemical Equations

  11. Checking for Balance • A balanced chemical reaction- both sides of equation have the same number of atoms of each element • Coefficients are used in front of the element or compound to balance. • Choosing coefficients - becomes easier with practice; trial and error at first

  12. Writing balanced chemical equations - 4 step process • Describe the reaction in words • Write the equation using formulas and symbols • Check for balance • Add coefficients where needed for balance

  13. Discussion Question • Why do chemical equations need to be balanced?

  14. Answer • Law of conservation of mass says mass will not be created or destroyed

  15. Section 3Classifying Chemical Reactions

  16. Types of Reactions 1. Synthesis Reaction- two or more substance form a new substance A + B --> AB 2. Decomposition Reaction-One substance breaks down into two or more substances AB ---> A + B 3. Single-displacement Reaction- one element replaces another one in a compound; A + BC ---> AC +B or D + BC --> BD + C 4. Double-displacement Reaction- results if a precipitate, water, or a gas forms when two ionic compounds in a solution are combined; AB + CD --> AD + CB 5. Combustion Reaction-a substance combines with oxygen to produce energy “X” + O2 --> CO2 + H2O

  17. Oxidation-Reduction (Redox) These reactions often involve oxygen • Oxidation • Loss of electrons • Substance becomes “oxidized” • Reduction • Gain of electrons • Substance becomes “reduced”

  18. Discussion Questions 1. What two chemical reactions are “opposites” of each other and why? 2. What are the 5 types of chemical reactions?

  19. Answers • Synthesis and decomposition • synthesis multiple substances combine to form a new one • decomposition a single substance breaks apart into multiple simpler substances • Synthesis, decomposition, single-displacement, double-displacement, combustion

  20. Section 4 Chemical Reactions and Energy

  21. A. Chemical Reactions involve energy exchange • Exergonic-Breaking chemical bonds release energy • Endergonic-Forming chemical bonds requires energy • Exothermic-Chemical Reaction where energy is primarily given off in the form of heat • Endothermic-Chemical reaction that requires heat energy in order to proceed

  22. B. More energy out • A catalyst speeds up a chemical reaction without itself being permanetly changed • An inhibitor prevents or slows a chemical reaction or interferes with the catalyst’s action

  23. Discussion Question • How are chemical bonds involved in energy exchanges?

  24. Answer • Breaking bonds release energy; forming bonds to require energy

More Related