30 Oct. Science 8 Recollecting WOW; Resuming Chemical Reactions

Quick look at the moon today for the morning class (period 8).

a. Mindful moment. Take a memory from the river flowing at WOW. Focus on that image. Breathe mindfully for a bit.

b. Review your previous DSN entries on chemical reactions.

c. Preview today’s blogpost.

d. Prepare entry for today. Writing on the river experience will go in the Earth Cycles folder. The rest of today’s work will be in the Matter folder.

e. Questions.

  • * * * *
  1. In your Earth Cycles folder, write a reflection on your experiences with flowing water at WOW 8. What did you learn about the river, about currents, rapids, white water, dynamics of flow, and other elements used to “read the river?” Relate your reactions and reflections to the response you wrote to Gary Snyder’s “We Wash Our Bowls with This Water” that we read in class before WOW.

2. Moon journal progress? Look at the rising and setting times: https://www.timeanddate.com/moon/india/new-delhi

3. Parent newsletter?

4.For the next part of the day, the entry will go in the Matter folder. If you do not finish all 11 items for today, consider them homework. Have everything ready for the next class as we will introduce the summative project for chemical reactions.

5. Conduct the following experiment and add your data to the spreadsheet. Your spreadsheet: https://docs.google.com/spreadsheets/d/1Aq2_2f6OCmZGEHzI04xRNITgz_IAdLBSJmke8rbw7eU/edit?usp=sharing

2017 Spreadsheet: https://docs.google.com/spreadsheets/d/18kjFLcw_LY_ojK5RFEh7sfCikb6U28rCPlQ6Gj0h50A/edit?usp=sharing

Sodium hydrogen carbonate (baking soda) and 5% acetic acid in water (vinegar)

What do you already know or think you know about the reaction between vinegar and baking soda? What do you think happens?

  • Wear eye protection.
  • Plastic bottle with tight-fitting lid. Totally clean and dry on the outside. Carefully find the mass of the bottle.
  • Add 50 ml vinegar to the bottle. Find the mass again.
  • Weigh 5 grams of baking soda on a tissue.
  • Gently bring the corners of the tissue together and make a small bundle.
  • Carefully put the bundle into the bottle. DO NOT LET the vinegar come in contact with the baking soda. They must remain separated.
  • Fit the cap so that the corners of the tissue bundle are held when the cap is tightlyclosed.
  • Find the mass of the closed bottle, tissue, baking soda, vinegar.
  • Gentle shake or turn the bottle so that the vinegar comes into contact with the tissue bundle of baking soda. Observe what happens.
  • When the reaction seems to slow / stop, find the mass of the bottle (still closed tightly) again.
  • Very slowly and carefully open the lid. Try not to let droplets of liquid fly out. After the gas is released. Find the mass of the bottle, lid, remaining liquid and tissue. Carefully smell the remaining contents. Compare to the smell of “fresh” vinegar.
  • Enter your data on the class spreadsheet.
  • Clean up the bottle. (No tissue down the sink!)

What do you think happened to the vinegar? What do you think happened to the baking soda? What do you think the gas might be? Where do you think the gas came from–the vinegar, the baking soda, both? How could you find out by experimentation?

6. Observe the use of the ball and stick molecular models to describe the reaction of acetic acid and sodium hydrogen carbonate (vinegar and baking soda).

The reactants are vinegar and baking soda. Vinegar is a solution of 5% acetic acid and 95% water. Baking soda is also called sodium hydrogen carbonate. The products are carbon dioxide, sodium acetate, and water. The reaction can be represented as: (NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO ).  Can you tell which symbols refer to which molecules?

See a representation of the reaction using “ball and stick” molecular models. See if you can follow the changes:

White ball = hydrogen; black ball = carbon; red ball = oxygen; silver ball = sodium; gray stick = bond (c0valent); purple stick = bond (ionic)

2 “rules” for reactions:

  • All atoms from the reactants end up somewhere–they do not disappear and new ones do not appear.
  • The reaction takes place in the fewest number of steps.

A. startreactvbs

B.

midreactvbs

C.

endreactvbsCarry out the reaction yourself using the ball and stick models.

If this model is good, it should allow you to predict the combining amounts. Look at your periodic table. Find the atomic weights for each element in the reactants. Convert the atomic weights to grams. Remember that the acetic acid is diluted to 5%. How close is this predicted ratio of a complete reaction to your empirical amount? If your empirical result is hugely different from your predicted amount, how do you resolve this discrepancy? Why do you think there is a difference? What can you do to check your work–empirical and mathematical (theoretical) and the thinking/reasoning?

7. Review and share your Matter chart that links observations with explanations.

8. Read this document Fundamental questions about matter  or

Fundamental-questions-about-matter

9. Identify the parts for which you have examples in your own experience.

10. Identify the parts for which you have questions.

11. Review your understanding of atom, molecule, element, compound, physical change, chemical change/chemical reaction, mass, volume, conservation of mass, states of matter, boiling point temperature plateau, freezing point temperature plateau, dissolving, solution, precipitation, crystallization, crystal form, evaporation, rate of reaction, histogram, density, evidence, argument.

10. Note any questions that you have.

 

About rfrazier

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