Student Activities for Acids and Bases
Acids and Bases Background
The ancient Greeks, who were early pioneers of chemistry, started to categorize different substances based on how they tasted (although this is not a great idea in the modern lab!). The categories they used were salty, sweet, sour, and bitter. The Romans inherited this idea and started to refer to sour substances as acids. The word acid is derived from the Latin, acere, meaning "to be sour". The word alkali comes from Arabic, ḳalā, meaning "to roast", and is thought to have come from Greeks mixing ashes with animal fat to make soap. In modern-day chemistry, we use the term base to describe a substance that can neutralize an acid. An alkali is a special type of base that can dissolve in water.
Acids are infamous for their corrosive properties, but bases can cause a lot more damage. Both acids and bases can corrode skin, leaving serious disfigurement, and they can also cause blindness if they get into your eyes. Not all acids and bases are dangerous though. Many of the foods we eat and enjoy are acidic or basic. Lemon juice is quite a strong acid and baking soda is a base!
How acidic or basic a substance is can be measured on the pH scale. This is an inverse logarithmic scale from 1-14. A strong acid is a 1, 7 is neutral (a substance which is neither acidic or basic) and 14 is a strong base. The scale is a measure of the hydrogen ion (H+) and hydroxide ions (OH-) in the substance. If there is an excess of H+ ions, then the substance is acidic. If there is an excess of OH- ions, then the substance is basic (or alkaline). A universal indicator is a substance that is often used in the lab to measure the pH of a substance. It is a mixture of dyes that gradually changes color depending on the pH. If it turns dark red, the substance is strongly acidic. Green would mean the substance is neutral with a pH of 7. Strong bases would turn the mixture of dyes a dark purple color.
Our stomachs produce hydrochloric acid, which is very useful in helping us digest food. Sometimes our stomachs can produce too much acid and cause heartburn. Medication is easily available to treat this in the form of antacids. An antacid medication’s active ingredients are bases or chemicals with a pH of more than 7. When the base reaches the stomach acid, it causes a neutralization reaction. Neutralizing the acid can reduce discomfort. We know a chemical reaction has taken place because new substances are formed. The word equation for this reaction is acid + base → salt + water.
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How Tos about Acids and Bases
Try a Simple pH Testing Activity with Everyday Items
Gather common household substances like lemon juice, baking soda, milk, vinegar, and dish soap. Provide students with universal indicator paper or solution and let them test each item to see its pH. Record results on a chart for a hands-on demonstration of acids and bases found around them.
Explain Safety Rules Before Handling Acids and Bases
Review classroom safety guidelines, such as wearing gloves and goggles, not tasting or touching substances, and washing hands after lab work. Emphasize that some acids and bases can be harmful, and proper precautions help everyone stay safe.
Encourage Students to Predict pH Results
Ask students to guess whether each household item is an acid or base before testing. Have them record their predictions and compare with actual results for an engaging way to practice scientific thinking.
Discuss Real-Life Uses of Acids and Bases
Lead a class conversation about where acids and bases are used at home or in daily life, such as cleaning products, food, and medicine. Connect classroom learning to practical examples students already know.
Have Students Create Colorful pH Charts
Let students make their own pH scale posters using colored markers or crayons to show acidic, neutral, and basic substances. This visual activity helps reinforce the pH concept and makes learning memorable.
Frequently Asked Questions about Acids and Bases
What is the difference between acids and bases in simple terms?
Acids have a pH less than 7 and taste sour, while bases have a pH greater than 7 and feel soapy. Acids can neutralize bases, and vice versa.
How can you quickly test if a substance is an acid or a base in the classroom?
Use a universal indicator. Add a drop to the substance—if it turns yellow/orange/red, it's an acid; if it turns blue/purple/black, it's a base.
What are some everyday examples of acids and bases students would recognize?
Common acids include lemon juice, vinegar, and soda. Everyday bases include baking soda, toothpaste, and dish soap.
Why is pH important in science lessons for kids?
pH helps students understand how substances interact, including reactions like neutralization, and introduces key chemistry concepts in a hands-on way.
What is a neutralization reaction and how does it work?
A neutralization reaction occurs when an acid and a base combine to form salt and water. This process helps balance pH, like how antacids relieve heartburn.
- calcium antacid tablet bottle • bradleygee • License Attribution (http://creativecommons.org/licenses/by/2.0/)
- DSCF8245 • jonseidman • License Attribution (http://creativecommons.org/licenses/by/2.0/)
- Lemon • KitAy • License Attribution (http://creativecommons.org/licenses/by/2.0/)
- PH • AHJulio • License Attribution (http://creativecommons.org/licenses/by/2.0/)
- river • Identity Photogr@phy • License Attribution (http://creativecommons.org/licenses/by/2.0/)
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