Grace UwaseJanuary 2016

Hell’s Kitchen

Description: This lesson uses various kitchen items to explore different types of chemical reactions.

Student will:1) Examine how different kitchen items react with each other 2) Test the pH of different kitchen items

Student will observe and understand that:1) Elements/atoms come together to form molecules and compounds2) Chemical reactions involve changes in properties like color and temperature3) Chemistry exist in everyday life4) The nature of a substance dictates how it responds to other reagents

Recommended: 6th to 8th grade Time required:

Class: 60-70 minutes, prep: 30-40 minutes

Key concepts:

Chemical reaction: A process in which two or more compounds produce a new compound. It can also be defined as a process that involves rearrangement of molecular structure.

Synthesis Reaction: Type of chemical reaction that occurs when two or more compounds combine to form a more complex compound.

Decomposition Reaction: Type of chemical reaction that occurs when a complex compound breaks down to form simpler compounds.

Single Displacement Reaction: In this chemical reaction, single element A replaces element B in a compound, to form another compound and single element B.

Double Displacement Reaction: In this chemical reaction, compounds swap elements to form new compounds.

Acid-Base reactions: These are chemical reactions, in which hydrogen is exchanged. Acid-base reactions are mostly double displacement reactions.

Materials:o Baking soda solution (2 table spoons

of baking soda+ 355 mL of water)o Red and blue litmus papero Vinegaro Lemon juiceo Red Cabbage juice o Bleacho Yeasto Hydrogen peroxide

o Watero Any kind of oil (optional)o Hand soapo Liquid starcho Iodine o Clear plastic egg holders or spot

plateso Plastic droppers o Waste container

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Safety Information: Students and instructor should wear protective goggles, but all materials used can be rinsed into the sink

Prep time:

1) Each team/student will need: 1 spot plate, set A of clue reagents (baking soda solution,

litmus papers, cabbage juice, yeast, and liquid starch), set B of answer solutions (vinegar,

lemon juice, bleach, hydrogen peroxide, hand soap, iodine), plastic pipets for each

reagent (12 per team), toothpicks for stirring, and a waste container.

2) Balanced chemical equations of the reactions that take place could be helpful, to visually

show the type of reaction that takes place.

BackgroundEveryone in this room is part of the “Keepers Society,” a society that is in charge of

keeping peace and protecting people from witches and evil magicians. This morning one of our

citizens could not wake up, and we found this note near her bed “Hello from the other side. She drank my red/pink drink, now you have to undo what was in my cup. It is the only way to wake her up. Follow the clues”. We followed some instructions that led us here, to “Hell’s Kitchen,” now we need to

figure out the clues to wake our citizen up.

Instructions (for the teacher):

Start by explaining that elements rarely exist in pure form, but they exist as molecules and

compounds. You can do a short activity where you start with individual students representing

elements, and bring them together to form teams, to represent molecules. When compounds

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come together, three things can happen: (1) they can react to form new compounds, chemical

reactions/changes, (2) they can interact without forming new compounds, physical changes, and

(3) they can just stay there without interacting, for instance water and oil. Give a brief discussion

on the types of reactions that we are going to see in the experiment, and you can use the

individual/team analogy to explain the types of reactions.

There are two sets of items labeled A and B. Set A contains items mentioned in clues, and they

will help students find the right item from set B. Once they find the item from B that fits the

description, they should write it on the “CLUES FOUND” worksheet. Encourage the students to

make detailed observations, as it will help them to make the connection between the clues, as

well as notice different ways things can interact with each other.

Clue number 1: pH will lead you home

This B item reacts with baking soda to form lots of bubbles, and it turns blue litmus paper red.

*They will find vinegar and lemon juice to work. Provide them with the equation of the reaction

that takes place and explain that most acid-base reactions are double displacement. It could be

also useful to briefly talk about what acids and bases are, and reference the pH scale. Emphasize

the NEUTRALIZATION that takes place when the two mix; this is an important clue. You can

also let students do a litmus test of baking soda before and after the reagents are added to

demonstrate neutralization. Point out that this particular reaction is both double displacement and

decomposition. The bubbles are CO2 that gets produced (depth of explanation will depend on age

group). ***Note that the litmus test is just to complement the acid-base discussion, and introduce

the idea of acid-base indicators. It is fine if there is not enough time, the litmus test can be

skipped or done after the experiment is completed.

NaHCO3(s) + CH3COOH (l) → CO2 (g)+ H2O (l) + NaCH3COO (aq)(Baking soda) (Vinegar)

NaHCO3 (s) + C6H5O7H (l) → CO2 (g)+ H2O (l)+ Na C6H5O7 (aq)(Baking Soda) (Citric Acid)

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Clue number 2: Colors will guide you there

This B item turns red cabbage juice colorless, and turns blue litmus paper white

*Bleach is the answer for this one. You can explain how bleach whitens things, by oxidation; it breaks down bonds of molecules that absorb color. Students should note how red cabbage juice reacts to each B item. Explain chemical basis of indicators. You can give this equation as an example of how bleach worksNaCl (s) + Na ClO (l)+ H2O (l) → Cl2 (g) + 2 NaOH (aq)

Clue number 3: it’s all bubbles and fun

This B item reacts with yeast to form lots of bubbles

*Hydrogen peroxide works. This is a decomposition reaction; H2O2 breaks down into oxygen gas and water, hence the bubbles. Talk about catalysts’ role in chemical and biological reactions2H2O2 (aq)→ 2H2O (l) + O2 (g)

Clue number 4: So dark down here

This B item turns purple when it reacts with liquid starch

*Iodine. Explain that this is a synthesis reaction, Amylose in starch and iodine form a blue compound. Allow them to make any other observations they can.

I2 (l)+ I-(aq) → I3-(aq)

I3- (aq)+ (C6H12O6) n (aq) → (C6H12O6) n I3

-(aq)

Clue number 5: Yes, I’m a giver

How good is your eye?

1) Take 2 drops of hand soap and add 15 drops of red cabbage juice2) Write what you see and write the word “dig under” on your clue sheet

* Students will be able to observe that a blue solution is formed. Discuss why this occurs, the nature of acid/base indicators. Refer to results in clue number 2, how acids responded to the indicator. This hints to the fact that the girl’s situation has something to do with acids and bases.

Clue number 6: It is NOT a clue

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You know that oil and water don’t mix…but you’re a chemist!

Ask the students to discuss how they can make oil and water mix using any ONE of the items provided (as a class or small groups). Give them three minutes to decide which item they would have to use.*The answer is “Hand Soap.” If students don’t come up with the correct answer, encourage them to try it at home or do a demo in class. Explain that this is not a chemical reaction, because neither water nor oil are changed. Their molecules are just broken to force interaction because of the amphipathic nature of soap.

Once they complete all the tasks, they will circle the first and fourth letter of each word on the clue sheet. Give each team a card containing this;

V=9E=4 and 19L=17O=2 and 11J=1C=13

B=16A=12H=6 and 10R=5P=20U=18

I=7 and 14D=3and 15S=8P=X

They will use the clue card to fill out the table and do a timed word search. Important words to find are acid, base, red, and blue. This is another clue.

Recap all the clue answers and ask them what the drink the girl consumed must have been, based

on the experiment. The answer is vinegar or lemon juice (an acid) mixed with red cabbage juice

(the red/pink drink). In front of the class, make the drink using about 10 mL of red cabbage juice

+ 10 mL of vinegar. Give them a few minutes to decide which two items would need to be mixed

in order to revive the girl.

*The answer is baking soda (a base) mixed with red cabbage juice. Explain why this is the right

drink by referring back to the neutralization of acid-base reactions, and make the drink to see that

it is blue as predicted. Now mix the pink with the blue drinks to demonstrate that acids and bases

do neutralize each other, the mixture should turn back to purple, the color of red cabbage juice

Special Notes and Costs: The complexity of this activity can be customized depending on how much chemical knowledge students have. The discussion of the actual chemical reactions and equations can be detailed or generalized.

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Plastic droppers can be bought from Amazon, about $12/500-container. Iodine solution can be bought at any drugstore—about $13/8oz at Walgreen. Clear plastic egg cartons work perfectly well, but spot plates can be purchased from flinnsci.com, $15/10 plates. http://www.flinnsci.com/store/Scripts/prodView.asp?idproduct=16254 . **this activity is best if the teacher facilitates it, to make sure that everyone is on the same page and it makes the goal of the experiment easier to achieve.

Sources:B., C. "The 5 Types of Chemical Reactions." Accessed January 12, 2016.

http://www.asd5.org/cms/lib4/WA01001311/Centricity/Domain/638/Five Types of Chemica Reactions.pdf.

"Equation for the Baking Soda and Vinegar Reaction." About.com Education. Accessed January 12, 2016. http://chemistry.about.com/od/chemicalreactions/f/What-Is-The-Equation-For-The-Reaction-Between-Baking-Soda-And-Vinegar.htm.

"Starch and Iodine Reaction." - MEL Chemistry. Accessed January 10, 2016. http://practicum.melscience.com/experiments/starch-and-iodine-reaction.html.

"The Catalytic Decomposition of Hydrogen Peroxide, II." The Catalytic Decomposition of Hydrogen Peroxide, II. Accessed January 12, 2016. http://chemed.chem.purdue.edu/demos/main_pages/19.7.html.

Instructions (For students)

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There are two sets of items labeled A and B. Set A contains items mentioned in clues and they will help you find the right item from set B. Once you find the item from B that fits the description, write it on the “CLUES FOUND” worksheet. Time is of essence; you have four minutes to complete each clue. Make good observations if you wish to awaken your citizen.

Clue number 1: pH will lead you home

This B item reacts with baking soda to form lots of bubbles, and it turns blue litmus paper red

1) Measure 10 drops of baking soda solution into five wells of a spot plate. 2) Add 5-10 drops of a different B item in each well on the plate, and note

which one(s) bubble. 3) Once you find any B item that bubbled, put 10 drops in a different well

and dip the tip of a blue litmus paper. If it turns red, write that B item down on the “CLUES FOUND” sheet.

4) Copy the equation of the reaction that takes place. Classify what type of chemical reaction it is. It can be more than one type.

Clue number 2: Colors will guide you there

This B item turns cabbage juice colorless, and turns blue litmus paper white

1) Measure 10 drops of cabbage juice in five wells on the spot plate2) Add 10 drops of each B item in individual wells, and NOTE how each B item

interacts with cabbage juice. Write down the B item that turns cabbage juice colorless.

3) Copy the chemical equation of B item that works, and write how cabbage juice reacts to each B item.

Clue number 3: it’s all bubbles and fun

This B item reacts with yeast to form lots of bubbles

1) Scoop small amounts of yeast in five wells 2) Add one pipet of each B item in the wells and note what happens. Write down

the one that bubbles3) Write the equation of the reaction that takes place.

Clue number 4: So dark down here!

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This B item turns purple when it reacts with liquid starch

1) Measure five drops of liquid starch into five wells. 2) Then add TWO DROPS of each B item and stir. Write the one that turns the

solution to deep purple.3) Write the chemical reaction that takes place.

Clue number 5: Yes, I’m a giver

How good is your eye?

1) Take 2 drops of hand soap and add 15 drops of cabbage juice.2) Write what you see and write the words “ dig under” on your clue sheet.

Clue number 6: It is NOT a clue

You know that oil and water don’t mix…but you’re a chemist!

1) At your table, discuss how you can make them mix using any ONE of the items at the table. You have three minutes.

2) Write down the answer on your clue sheet.

Once you complete all the tasks, circle the first and fourth letter of each word on your clue sheet.

My messenger will give you a card that will help you complete the blank table.

From the completed table, search for as many words as possible in two minutes.

Of all the items you have, two can be mixed to make a blue nontoxic solution that will help your citizen wake up. You have three minutes to decide at your table which two items to mix.

Mix 10 drops each of the two items you think will work.

CLUES FOUND

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Clue Number

B item(s) Any Observations

1

2

3

4

5

6

Fill the table below with letters using the card provided by the messenger.

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

Search for as many words as you can and write them in the lines provided.

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