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What would happen if you drank a glass of acid?
Chemical Magic Unit | Lesson 3 of 5
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What would happen if you drank a glass of acid?
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Chemical Magic Unit | Lesson 3 of 5
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IMPORTANT NOTE

THIS LESSON WAS REVISED ON JANUARY 11, 2018.

Click here to see the previous version.

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DISCUSS:

This probably isn’t the first time you’ve heard the word "acid." What does this word make you think of?

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Extensions

Below are ideas for extending this topic beyond the activity & exploration which you just completed.
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Readings

These readings will get students thinking about how acids help shape the world around us. Free with registration on ReadWorks, a nonprofit committed to providing teachers with research-proven, Common-Core-aligned readings.

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Activity: Color-changing foods

Pigments in purple cabbage and black beans change color in acid. This list from Thought.Co. suggests other natural color-changing pigments to experiment with.

Here are three of our favorites:

  • Blueberries — The juice turns red when you add acid.
  • Grape juice — Manufacturers add citric acid to bottled grape juice, making the purple juice red. Adding baking soda makes the juice less acidic, making it fizz and change color.
  • Turmeric — Mix this yellow spice with water. Add baking soda and it will change color. (A word of warning: turmeric can stain hands and clothing.)
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Activity: Make an Egg without a Shell

This is one of our favorite activities. You start with an ordinary chicken egg. Leave it in vinegar overnight & the acid dissolves the eggshell. You end up with a egg that’s held together by the flexible membrane inside the shell.

You’ll find detailed instructions on how to make a “naked egg” on the Exploratorium’s Science of Cooking website.

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Activities: Taste the fizz

You’ve seen that adding baking soda to acid makes it fizz. Here are two activities that use that fizz to make tasty treats.

New Zealand’s Science Kids explain you how to make fizzy lemonade.

The folks at Planet Science explain how to make a candy treat called sherbet. Watch out! This candy zaps your tongue with fizz.

Who knew science could be so tasty?

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Overview
Grade 5th
Topic Chemical Reactions & Properties Of Matter
Focus Acids, Reactions, & Properties of Matter
Print Prep
Activity Prep

THIS LESSON WAS REVISED ON JANUARY 11, 2018. Here is a link to the previous version.
In this lesson, students are introduced to acids, a group of substances with a reputation for being reactive. In the activity, Acid Test, students discover two ways to detect acids: they use baking soda, which fizzes when mixed with acids, or a special liquid that changes color when mixed with acids. Then, students use those methods to identify common foods that are acidic.

Preview activity

COVID-19 Adaptations
Digital worksheets available
Teacher demo recommended

Students at home
Set up the activity and demonstrate over video conference. Students need the Results worksheet (printed or digital) to record their observations.
Students at school
Set up the activity and demonstrate while students observe. Each student needs a Results worksheet to record their observations.
Number of students:
Acid Test Results worksheet 30 copies
Acid Test Results Answer Key teacher-only resource 1 copy
Mixing Sheet printout Print 15 copies
Testing & Acid Reaction Supply Mats printout Print 8 copies
Clean-up Supplies (Eg. Paper Towels)
1 roll
Purple Cabbage (Chopped)
You can use 7 ounces dried black beans instead, but purple cabbage works better.
Details
2 cups
Table Covering (eg. Trash Bags)
16 bags
1 Acid
You can use lemonade, ketchup, mustard, pickle juice, or yogurt.
Details
8 tablespoons
Baking Powder
8 tablespoons
Baking Soda
8 tablespoons
Coffee Stirrers
Craft sticks or spoons will also work.
Details
32 sticks
Dixie Cups (3 oz)
56 cups
Measuring Cup
1 cup
Measuring Spoons
1 set
Plastic Bin
Must hold at least 4 cups of water. Used to make your indicator liquid. You can also use a gallon-sized Ziploc bag.
Details
1 bin
Plastic Straws (Not Bendable)
20 straws
Salt
1 cup
Sheet Protector
You can also use taped-down waxed paper or Press n' Seal.
Details
15
Toothpicks
30 toothpicks
White Vinegar
1 cup
Prep Instructions

You will need access to water for this activity.

We suggest students work in pairs and two pairs of students share supplies at the same table group. Homeschool students can work on their own.

Prepare the Purple Indicator Liquid

If you’re using purple cabbage, put 2 cups of chopped cabbage in 1½ cups of water. Leave it for at least an hour, stirring occasionally. The cabbage will turn the water purple. Drain the chopped cabbage and reserve the purplish-pink liquid. If you’re using black beans, put 1 cup of beans into 2 cups of water and leave them for at least an hour. The beans will soak up some water and turn the rest purplish brown. Drain the beans and reserve the purplish-brown liquid.

Prepare the Straws

Cut each straw in half to make two short straws. Students will use these to transfer drops of liquid. (Full-length straws are likely to tip over cups.)

Prepare the Testing & Acid Reaction Supplies

Gather all of your Dixie cups and separate them into seven equal piles. You will fill the cups in each of these piles with a different liquid or powder.

  • Water Cups: Add 2 tablespoons of water.
  • Vinegar Cups: Use a permanent marker to label each of these cups with a “V” so students can quickly tell these apart from the water. Add 2 tablespoons of vinegar.
  • Baking Soda Cups: Add 2 tablespoons of baking soda. (You may want to tell students that baking soda is different from baking powder.)
  • Baking Powder Cups: Use a permanent marker to label each of these cups with a “BP” so students can quickly tell these apart from the baking soda. Add 1 tablespoon of baking powder.
  • Purple Indicator Cups: Add 1 tablespoon of the purple indicator liquid that you prepared.
  • Unknown Substance “A” Cups: Add 1 tablespoon of an unknown substance. We suggest using an acid such as lemonade, ketchup, mustard, pickle juice, or yogurt (there are many acids in the kitchen).
  • Unknown Substance “B” Cups: Add 1 tablespoon of a different unknown substance. We suggest a non-acid such as salt water. (You can mix 1 tablespoon of salt into a cup of water.)

Separate Supplies for Easy Distribution

We recommend you set up four supply stations.

Station A: Acid Reaction Supplies

  • “Acid Reaction Supplies” printouts
  • Water Cups
  • Vinegar Cups
  • Straws (2 per group)

From this station, each group of students will bring the following back to their desk:

Acid Test Station A

Station B: Testing Supplies

  • “Testing Supplies” printouts
  • Baking Soda Cups
  • Baking Powder Cups
  • Purple Indicator Cups
  • Stir Sticks (2 per group)
  • Straw (1 per group)

From this station, each group of students will bring the following back to their desk:

Acid Test Station B

Station C: Worksheets & Clean-up Supplies

  • "Mixing Sheet" printouts
  • "Results" printouts
  • Sheet Protector
  • Paper Towels

From this station, each pair of students will bring the following back to their desk:

Acid Test Station C

Station D: Unknowns

  • Unknown Substance “A” Cups
  • Unknown Substance “B” Cups
  • Straws (1 or 2 per group, depending on unknown substance type)
  • Stir Sticks (1 or 2 per group, depending on unknown substance type)
  • Toothpicks

From this station, each pair of students will bring the following back to their desk:

Acid Test Station A

Teacher Background

The purple liquid that you prepare from the cabbage (or black beans) is called an indicator. There’s a pigment in purple cabbage and black beans that changes color when it reacts with an acid or base. You and your students should notice that the color of the liquid changes to a reddish/pink when you add it to any of the acids (e.g. vinegar). You can then use this information to test unknown liquids. If the liquid turns pink, then it’s an acid. You can learn more about indicators here.

You and your students will also notice that when baking soda is mixed with vinegar, there is fizzing that indicates an acid-base reaction. But baking soda does not fizz when mixed with water, making it a good acid indicator. Baking powder will also fizz with vinegar. But you will notice that baking powder will also slightly fizz when water is added. This is because baking powder is actually a mixture of baking soda (base) and cream of tartar (acid). This is why it reacts with both water and vinegar. So baking powder is not a good indicator because it fizzes when any liquid is added.

Overview
Grade 5th
Topic Chemical Reactions & Properties Of Matter
Focus Acids, Reactions, & Properties of Matter
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