Acids and bases are everywhere in our lives. Our stomachs produce hydrochloric acid to help us digest food and to protect us from infectious disease. Acids are also present in many sour tasting foods. Bases are used in bleach for cleaning and many other processes. People often recall the corrosive properties of acids, but are often unaware that bases can be just as corrosive, if not more dangerous. How acidic or basic a substance is can be measured using the pH scale. We can measure the pH of a chemical by adding a universal indicator to it. The color the indicator turns gives us an idea of the pH.
Acids and Bases Lesson Plans, Student Activities and Graphic Organizers
The pH scale is used to compare different substances and identify how acidic or basic they are. A pH of 1 is a strong acid, and a pH of 14 is a strong base. If a substance has a pH of 7, it is said to be neutral (not acidic or basic). Have your students demonstrate their understanding by creating their own version of the pH scale.
Students will link together the strength of the acids and bases and their corresponding pH value. Students will also review the colors a universal indicator turns when it is mixed with acids and bases.
Alternatively, have students complete this assignment after testing different substances in the lab. Students recreate the pH scale choosing the colors they found for the different substances they tested.
Have your students put key vocabulary into practice. One of the things students can find really difficult is using scientific vocabulary correctly and in the appropriate context. Using a visual representation or visual examples as well as a written one can really help students understand abstract concepts.
Example Acids and Bases Vocabulary
A chemical substance with a pH lower than 7 is an acid.
A chemical substance with a pH higher than 7 is called a base.
A chemical that has a pH of exactly 7 is described as being neutral.
A base that can dissolve in water is called an alkali.
A universal indicator is a mixture of dyes that changes color to indicate the pH of a substance.
Discussion storyboards are a great way to get your students talking about their ideas in Science. They allow students to critique and evaluate different viewpoints without upsetting other students. This activity can be used at the start of the topic to elicit any misconceptions students may have.
At first, show students a discussion storyboard like the one below. Ask them to look at the problem on the discussion storyboard. It shows four students who all have an idea about the problem in front of them. Students should think about whom they think is the most correct and be prepared to explain why that person is correct.
Here are some other ideas to use these discussion storyboards in your lessons.
Students add another cell on the end of the example you’ve given them to explain whom they think is correct and why.
Students create their own discussion storyboards to share with peers on the current topic.
Note that the template in this assignment is blank. After clicking "Copy Assignment", add your desired problem and solutions to match the needs of your students.
Have your students collate a range of examples of substances that are acidic, basic, and neutral using this Storyboard That graphic organizer. Students need to place the given examples into the three categories: Acid, Neutral, and Base.
To make this activity more challenging, have students research different substances to put in each category instead of providing a list.
As an extension, have students place the substances in order of pH from the most acidic to the most basic.
When we combine an acid and a base, a chemical reaction takes place. This chemical reaction is called neutralization. The equation for this reaction is: acid + base → salt + water. For example, if we mix hydrochloric acid with sodium hydroxide, they will react and produce sodium chloride and water. There are many examples where this is useful. If a stomach produces an excess of acid, this can cause indigestion. Taking medication, such as milk of magnesia (which is basic), can neutralize the acid and relieve the discomfort.
Have your students look at the practical applications of neutralization. Have students use books and the internet to research these and then display them in a spider map storyboard. They can support their writing with visual elements.
The ancient Greeks, who were early pioneers of chemistry, started to categorize different substances based on how they tasted (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", 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 of their corrosive properties, but bases can cause a lot more damage. Both acids and bases can corrode skin, leaving seriously 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 as new substances are formed. The word equation for this reaction is acid + base → salt + water.
Acids have a pH of less than 7.
Dilute acids can irritate the skin.
Concentrated acids can be corrosive.
The universal indicator turns yellow/orange/red when added to an acid.
Acids taste sour.
Acids can neutralize a base.
Bases have a pH of more than 7.
A base that dissolves in water is called an alkali.
Diluted bases can irritate the skin.
Concentrated bases can be corrosive.
Universal indicator turns blue/purple/black when added to a base.
Bases feel soapy.
Bases are used in cleaning products and used in antacids (medication to help upset stomachs).
Bases can neutralize an acid.
Essential Questions for Acids and Bases
What is an acid?
What is a base?
What happens when you mix an acid and a base?
What is pH?
Additional Acids and Bases Lesson Plan Ideas
Have students make a narrative storyboard showing the journey of an antacid tablet.
What would life be like without acids and bases? Have students make a storyboard to describe a world without them.
Get your students to research the discovery of acids, alkalis, and bases and create a timeline describing the major milestones.