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Ch. 7 Chemical Reactions: An Introduction

Ch. 7 Chemical Reactions: An Introduction . Aya Abdellatif , Amanda Kang, Ishrat Mannan, Moriah Smith. Section 1 : Evidence for a Chemical Reaction . Chemical Reaction : A change in which a substance is changed into one or more new substances. Chemical reactions are not always visible

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Ch. 7 Chemical Reactions: An Introduction

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  1. Ch. 7 Chemical Reactions: An Introduction AyaAbdellatif, Amanda Kang, Ishrat Mannan, Moriah Smith

  2. Section 1 : Evidence for a Chemical Reaction • Chemical Reaction: A change in which a substance is changed into one or more new substances. • Chemical reactions are not always visible • Change in temperature and/or heat being produced or absorbed can indicate a chemical reaction

  3. Section 1 Cont. • You can often tell if a chemical reaction has occurred by visual clues given : • General Clues Are: • A flame is produced • Color change • Bubbles are produced • A solid forms • More Specific Examples • Hair changing colors • Metal rusting

  4. Section 2 : Chemical Equations • Chemical reaction : when one or more substances are changed into one or more new substances by the reorganization of component atoms • Chemical equations : a representation of a chemical reactions using the formulas of the starting substances that react (reactants) and the new substances that are formed (products)

  5. Section 2 Cont. • In a chemical reaction, atoms are neither created nor destroyed • All atoms present in the reactants must be accounted for among the products • Making sure that the equation for a reaction obeys this rule is called balancing the chemical equations • Balanced chemical equation : shows the actual numbers of molecules involved in this equation • In the equation the physical state the of reactants and products are indicated: • Solid (s) • Liquid (l) • Gas (g) • Dissolved in solution/ Aqueous solution (aq)

  6. Section 3 : Balancing Chemical Equations • Atoms are conserved in a chemical reaction • The same number of each type of atom is found in the reactants and products • The formulas of the compound must never be changed in balancing a chemical equation • Coefficient: the number written in front of the chemical formulas in a balanced chemical equation that indicate the relative numbers of reactants and products in the reaction • Placing coefficients in front of the formula is how to balance an equation

  7. How to Write a Balanced Equation • Step 1: Read the description of the chemical reaction • State the reactants, products and their states • Write appropriate formula • Step 2: Write unbalanced equation • Step 3: Balance the equation • Proceed element by element to determine what coefficients are needed so that there is an equivalent number of atoms on the reactant and product side • don’t change the formulas of any of the reactants or products • Step 4: Check and make sure that the coefficients used give the same number atoms on both sides of the equation • Make sure that the coefficients used are the smallest whole number by determining whether or not all the coefficients can be divided by the same whole numbers to get a smaller set of whole numbers.

  8. Situation #1 • Solid Potassium reacts with liquid water to form gaseous hydrogen and potassium hydroxide

  9. Situation #2 • Ammonia gas reacts with oxygen gas to produce gaseous water and nitrogen monoxide

  10. Quiz Time! 1.List two examples of how you can visually tell if a chemical reaction has occurred. 2.Write down a real-life example of a chemical reaction. 3.True or false. A chemical reaction is when one or more substances are changed to make new substances. 4.Fill in the blank; In a chemical reaction, atoms are netither ______ or _______ 5.Briefly explain in one sentence the rule of balancing chemical equations.

  11. Quiz time, continued 6.Write how solids, liquids, gases, and dissolved in solution/Aqueous. 7.For balancing an equation, the same number of each type of atom is found in the _____ and ______. 8.________ is the number written in front of the chemical formulas in a balanced equation. 9. What are the steps 1-3 of writing a balanced equation?

  12. Answers 1.Possible answers: flame is produced, color change, bubbles are produced, solids are formed. 2.Answers vary 3. True 4. Created or destroyed 5. Basically, all atoms present in the reactants must be accounted for among the products. 6.(s)(l)(g)(aq)

  13. Answers cont. • 7. reactants and products • 8.Coefficient • 9.Step 1: Read the description of the chemical reaction. Step 2: Write unbalanced equation. Step 3: Balance the equation. • HOPE YA DID WELL :D Tootsie rolls for the winners

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