4.1 Intro to Stoichiometry

A powerpoint to guide students through balancing chemical equations.

Transcript

1. Do Now • Pick up guided note sheet from Pick Me Up Table • Pick up index card • Our next unit talks about chemical reactions and is the basis of chemistry. In this unit you will be able to describe chemical reactions as well as see how they apply to the world we live in. What do you want to learn about chemical reactions? What makes you nervous about this unit (if applicable)? Write 3-5 sentences answering the questions above. on your index card
2. Announcements ! • Lab write-ups are due on Friday ᾶ No exceptions! • Our assignments so far: – Density HW – Density Lab – Unit 3 Written Test – Unit 3 Lab Assessment (Due Friday) • If any of these sound unfamiliar, you need to see me!
3. UNIT 4 ᾶ STOICHIOMETRY AND SOLUTIONS PART 1
4. LECTURE 4.1 ᾶ BALANCING CHEMICAL REACTIONS
5. Todayᾼ s Learning Targets • I can determine how many atoms are in a molecule. • I can balance a chemical reaction
6. What is a chemical reaction? • While this video plays, write down 2 things that you think represents a chemical reaction • They can be whatever you want! • Be prepared to share 1 or 2 things with a partner when the video is done.
7. What is a chemical reaction? • What did we write down? I need 3 people to share and then I have a story for you
8. How do elephants brush!?
9. I. Chemical Reactions • Substances react to form new substances • Chemical equations are used to explain a reaction that occurs. • H2O2  H2O + O2 • Hydrogen Peroxide  Water + Oxygen
10. II. Chemical Reactions Reactants  Products Reactants Products H2O2  H2O + O2
11. States of Molecules • A molecule can be in a solid, liquid, gas, or aqueous state • Aqueous means dissolved in water • We abbreviate these as: – (s) = solid – (l) = liquid – (g) = gas – (aq) = aqueous
12. Table Talk • With your table, circle the products, square the reactants, and label the state of each compound. NH4OH (aq) + FeCl3 (s)  NH4Cl (s) + Fe(OH) 3 (aq) aqueous solid solid aqueous
13. How do you balance chemical reactions?
14. I. Balancing Chemical Reactions • Law of conservation of mass - Need same amount of products and reactants • For this, we need to know how to count
15. Letᾼ s Count NH4 Molecule Nitrogen Atoms Hydrogen Atoms How many N atoms do you have? How many H atoms do you have?
16. Letᾼ s Count H2O Molecule Hydrogen Atoms Oxygen Atoms How many H atoms do you have? How many O atoms do you have?
17. Letᾼ s Count 2H2O Molecule Hydrogen Atoms Oxygen Atoms How many H atoms do you have? How many O atoms do you have?
18. Letᾼ s Count Ca(OH)2 Molecule Calcium atoms Oxygen Atoms How many Ca atoms do you have? How many O atoms do you have? Hydrogen Atoms How many H atoms do you have?
19. Tips for Balancing Chemical Reactions • Do NOT change the subscripts, only change the coefficient • Must have same number of each atom on both sides! 2 NH3 Coefficient This means we have 2 N and 6 H atoms Subscripts
20. Class Example • Balance the following chemical reaction: ____H2O2  ___ H2O + ____O2 Reactants Products
21. Table Talk • Balance the following chemical reaction _3___Mg + ___2__FeCl3  _3_MgCl2 + __2___Fe Reactants Products
22. Salsa Ladder ᾶ Climb with Post Its
23. Exit Ticket 1. What does the law of conservation of mass state? 2. Label the products and reactants in the following reaction NaOH + HCl  NaCl + H2O 3. Balance the following equation. __ NH4OH + __ FeCl3  __ NH4Cl +___ Fe(OH) 3
24. Extra Examples • ___ C3H6 + ____ H2O  ___ C3H8 + __ O2 • ___ Mg + ___ FeCl3  ___ MgCl2 + ___ Fe • __ H2O + __ Fe2 (SO4) 3  __ Fe2O3 + __ H2SO4 + ___ H2O + ___ H2
25. Balancing Chemical Reactions with Candy • Each candy piece represents one element or atom. • The problem will tell you what each candy represents.
27. Closing Time Closing Time • Homework 3.1 due Tuesday/Wednesday • Quiz on Balancing Equations Thursday/Friday