Acids, Bases and the pH Scale | Montessori Chemistry Experiments and Activities

Make Acids, Bases and pH Understandable—Not Just Memorable

Acids and bases are all around us, but the language of pH, acidity, alkalinity and neutralisation can quickly become abstract for elementary learners.

Children may remember that lemons are acidic or that the pH scale runs from 0 to 14, yet still struggle to explain what those facts mean, how scientists test a substance or why pH matters in everyday life.

This 28-page acids, bases and pH introduction gives you a practical, sequenced way to teach the topic.

Children begin with accessible background information and a visual pH scale. They then investigate the concepts through guided experiments, scientific-process work, classification games and a challenge to design their own experiment.

Instead of completing isolated chemistry worksheets, learners build knowledge step by step and apply it through observation, prediction, testing and discussion.

A Complete Introductory Chemistry Sequence

Finding an experiment that produces an exciting colour change is easy.

The harder part is helping children understand why the change occurred, how it relates to the pH scale and how to record an investigation scientifically.

This resource brings those parts together in one connected sequence:

1. Introduce acids, bases and pH through clear reading and discussion.
2. Use a visual pH scale to connect unfamiliar numbers with everyday substances.
3. Carry out guided experiments that develop observation and comparison skills.
4. Explicitly introduce the scientific process within a meaningful context.
5. Apply the learning through games, classification and real-world examples.
6. Invite children to design an investigation of their own.

This structure makes the resource suitable for teaching across several lessons rather than trying to introduce the entire topic in one sitting.

What Is Included?

Introductory Reading and Vocabulary

• A one-page reading comprehension introducing acids, alkalines or bases, and pH
• Clear explanations written for elementary-aged learners
• Connections to familiar substances and everyday experiences

Visual pH Scale

• A full-colour pH scale featuring real-world examples
• A black-and-white version for note-taking, labelling or student activities
• A visual reference that can be displayed or placed on the science shelf

Hands-On pH Investigations

• Four guided pH experiments
• Opportunities to predict, observe, compare and record results
• A Design Your Own Experiment challenge for children ready to apply their learning more independently

The Scientific Process

• A one-page introduction to the scientific process
• A two-page linked assignment that guides children through the stages of an investigation
• Support for developing questions, making predictions, recording observations and drawing conclusions

Games and Real-Life Application

• A Zap Game for identifying common household acids and alkalis
• A sorting activity connecting pH knowledge with everyday situations
• Interactive follow-up work suitable for repetition or partner learning

Teacher Guidance

• Clear instructions for preparing and presenting the activities
• A flexible format that can be adapted for classroom or homeschool use

Begin With Things Children Already Know

Children may have heard that lemons and vinegar are acidic or seen baking soda react with another substance. This resource uses those familiar experiences as an entry point into more precise scientific understanding.

As they work through the material, children explore questions such as:

• What makes a substance acidic or alkaline?
• What does a pH number tell us?
• What does it mean for a substance to be neutral?
• How can an indicator help us test an unknown substance?
• What happens when some acids and bases are combined?
• Why does pH matter in soil, food, water, health and household products?

The aim is not simply to memorise the scale. It is to help children interpret information, make connections and think scientifically.

Hands-On Science With Academic Purpose

Experiments often generate enthusiasm, but children need support to move beyond watching something happen.

The guided investigations encourage learners to:

• ask questions before beginning
• make a reasoned prediction
• follow a procedure carefully
• observe changes closely
• record results clearly
• compare substances
• consider whether the evidence supports their prediction
• suggest further questions or investigations

Because the scientific process is introduced alongside actual investigations, it becomes a useful working method rather than a separate list of vocabulary to memorise.

Designed for Montessori and Mixed-Age Learning

This resource can begin with a teacher-led presentation and then be separated into smaller activities for the shelf.

For example, you could offer:

• the introductory reading and pH chart as one activity
• one guided experiment at a time
• the Zap Game as partner work
• the real-life sorting cards as independent classification work
• the scientific-process assignment for older or more confident writers
• the experiment-design challenge as an extension

This gives children different ways to enter the same topic without expecting every learner to complete identical work.

The visual references, clear stages and interactive elements may be particularly helpful for neurodivergent learners and children who benefit from explicit structure, repetition and concrete examples.

Suggested Teaching Sequence

1. Activate prior knowledge. Show children familiar household substances and discuss what they already know about acids and bases.
2. Introduce the vocabulary. Use the reading page to establish the meanings of acid, base or alkaline, neutral and pH.
3. Explore the pH scale. Compare the examples and discuss what lower, neutral and higher pH values represent.
4. Complete a guided experiment. Model how to predict, observe and record.
5. Introduce the scientific process. Connect each stage directly to the experiment the children have completed.
6. Repeat and compare. Complete further investigations and encourage children to identify patterns.
7. Consolidate. Use the Zap Game and sorting activity to review terminology and everyday applications.
8. Extend. Invite children to plan their own pH investigation.

Extend the Learning

Children could use this pack as the starting point for further investigations into:

• testing safe household substances with pH paper
• creating a classroom pH scale using tested examples
• natural indicators such as red cabbage
• how soil pH affects plant growth
• the importance of pH in pools, aquariums or drinking water
• acidic and alkaline foods
• tooth enamel and acids
• ocean acidification
• neutralisation reactions
• how scientists control variables and improve an experiment

Older learners could also compare their results, graph pH measurements or evaluate which parts of an investigation need to remain controlled.

Created for Real Montessori Learners

I am a Montessori-trained teacher, New Zealand registered teacher, school principal and former homeschooler.

I create resources from real experience teaching mixed-age learners, including neurodivergent children and children working at different reading, writing and independence levels.

My resources are designed to make substantial concepts accessible without reducing science to disconnected worksheets or entertainment-only experiments. They provide clear teaching support while still encouraging curiosity, repetition and independent inquiry.

Important Safety Information

• All experiments should be completed with appropriate adult supervision.
• Only use substances that are suitable and safe for children in your setting.
• Children should never taste experimental substances.
• Do not assume that a substance is safe because it is described as an acid, alkaline or household product.
• Use eye protection, gloves and protective surfaces where appropriate.
• Review the ingredients and possible reactions before combining any substances.
• Adapt the activities to meet your school, homeschool or local laboratory-safety requirements.

Digital Download Information

• This resource is supplied as a 28-page printable PDF.
• No physical product or experiment materials will be mailed.
• You will need to gather the relevant household materials and testing equipment.
• Purchase permits use by one classroom or one homeschool family.