Properties of Acids and Bases: Alien Juice Bar Lab

Properties of Acids and Bases
Free Physical Science Lab Activities

Properties of Acids and Bases Lab

The objective of this lab is to engage students in an interactive activity to learn about the properties of acids and bases within the pH scale.

Due to the exploratory nature of the activity each student’s charts and conclusions will be different.

The goal is to have the students develop an understanding how acids and bases can affect each other in large or small increments depending on the amounts mixed and where they are on the pH scale.

Here are the files for the Properties of Acids and Bases Lab Activity:

Alien Juice Bar Lab Procedure:

Background Information:

Scientists use the pH scale to describe the concentration of hydrogen protons in a solution. Acid-base indicators are chemicals used to determine whether an aqueous solution is acidic, neutral, or alkaline. Since acidity and alkalinity relate to pH, they may also be known as pH indicators. A pH of 7 means that the solution is neutral, which means it is neither basic or acidic. A pH less than 7 means the solution is acidic while a pH greater than 7 means the solution is basic. The lower the pH, the more acidic a solution is. Some examples of acid-base indicators are litmus paper, phenolphthalein, and red cabbage juice.

Red cabbage contains a water-soluble pigment called anthocyanin that changes color when it is mixed with an acid or base. It is just one of the many indicators that are available to scientists. Some indicators start out colorless and turn different colors when they mix with an acid or base. Some substances do not show any change in color which indicates it is neither acid or base.

pH Scale Properties of Acids and Basis - Properties of Acids and Bases

Red cabbage indicator by Epaenurk is licensed under CC 3.0 via Wikimedia Commons.

In this laboratory activity, you will make your own red cabbage indicator and you will use this to determine the acidity and alkalinity of common household materials.

Learning Objectives:

At the end of this laboratory activity, students are expected to:

  • Make a red cabbage acid-base indicator.
  • Test the acidity and alkalinity of common household materials using the red cabbage indicator.

Pre-lab Prediction:

Look at each of the liquids that will be tested in this activity. Predict whether each of the substance is acidic, neutral, or basic. Put a check in the correct column to show your answer.

Substance Acidic Basic Neutral
hand sanitizer
lemon soda
apple juice
white vinegar
baking soda
shampoo
conditioner

Laboratory Proper:

Materials:

·       pre-cut red cabbage

·       blender

·       strainer

·       large container

·       1 L beaker

·       7 plastic cups

·       7 plastic spoons

·       lemon soda

·       white vinegar

·       apple juice

·       baking soda

·       shampoo (preferably clear)

·       conditioner (preferably clear)

·       hand sanitizer

Safety Alert! Some household materials are toxic by ingestion and can cause eye irritation. Avoid contact of all solutions with eyes. Clean up spills immediately. All food-grade items that have been brought into the lab are considered laboratory chemicals and are for lab use only. Do not taste or ingest any material in the lab. Wear safety goggles, gloves, and laboratory apron as you perform this activity. Wash hands thoroughly with soap and water before leaving the laboratory.

Properties of Acids and Bases Procedure:

  1. Put the cut red cabbage leaves into the blender with 800mL of water.
  2. Cover the blender and let it blend at high power for 30 seconds.
  3. Once it is blended, pour the mixture onto a large container with strainer on top to filter out its leaves. You can squeeze the leaves to get the remaining extract.
  4. Prepare the liquids to be tested by labeling each cup with its name. (Example: vinegar, apple juice, lemon juice, etc)
  5. Pour 100 mL of each individual liquid into its respective cup except for the baking soda.
  6. Prepare the baking soda mixture by adding 3 tablespoons of baking soda into 100 mL of water.
  7. Pour 50 mL of red cabbage juice into each of the cups. Do this one at a time.
  8. Record the changes in color for each liquid in Table 1. Use the table below to indicate its approximate pH and determine whether it is an acid or a base.
Color Pink Dark Red Violet Blue Blue-Green Green-Yellow
Approximate pH 1 – 2 3 – 4 5 – 7 8 9 – 10 11 – 12
Acid/Base Acid Acid Acid/Neutral Base Base Base

 

  1. Look up the actual pH of each substance and see how accurate the red cabbage indicator was.

Observations:

Table 1: Result of Red Cabbage Indicator in Common Household Substances.

Household Substance Color Change Approximate pH Actual pH
lemon soda

 

white vinegar

 

apple juice

 

baking soda

 

shampoo

 

conditioner

 

hand sanitizer

 

 

Post-lab Questions:

  1. What is in red cabbage that makes it a good acid-base indicator?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

 

  1. How does the red cabbage indicator work?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

  1. Based on the actual pH of the household substances you used in this activity, do you think the red cabbage indicator is accurate? Why or why not?

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

 

  1. Research one fruit or vegetable that can also be used as an acid-base indicator. Write down the substance it contains that can make it a good acid-base indicator.

____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

The Properties of Acids and Bases Activity:

Students record their predictions and results of the lab activity. Once the activity is finished, discuss the lab activity and answer post-lab questions.

We also provided some of the Resources below for you to use in class. iTeachly Members can access all the content for the activity and the following lesson.

Students must come up with a unanimous answer for each question. Discussing the answers usually, results in some excellent dialogue on this topic.

Here is your Free Content for the Properties of Acids and Bases Part of the Lesson!

Properties of Acids and Bases- PDFs

Properties of Acids and Bases Worksheets - Word Docs & PowerPoints

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Properties of Acids and Bases

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