Everyday Acids and Bases

Acids and bases are not just chemicals found in laboratories. They are present in foods, drinks, medicines, cleaning products, cosmetics, and even inside our bodies.

Understanding acids and bases helps us explain why certain products taste sour, why cleaners remove grease, how antacids work, and why controlling pH is important in our everyday lives.

Acids Around Us

Many common foods and drinks contain weak acids.

Examples include:

These substances are acidic because their aqueous solutions contain hydrogen ions (H⁺).

Lemon and Citrus Fruits

Lemons, oranges, limes, and grapefruits contain citric acid.

Citric acid gives these fruits their characteristic sour taste. It is also added to many foods and drinks as a flavouring and preservative.

Vinegar

Vinegar contains ethanoic acid, also called acetic acid.

Vinegar is commonly used for:

• cooking
• pickling food
• removing some mineral deposits
• household cleaning

Carbonated Drinks

Many carbonated drinks are acidic. Dissolved carbon dioxide reacts with water to form carbonic acid, while some drinks also contain acids such as phosphoric or citric acid.

Frequent exposure to acidic drinks can contribute to the erosion of tooth enamel.

Bases Around Us

Bases are also common in homes and schools.

Many household bases are found in cleaning products and medicines.

Why Are Bases Used in Cleaning Products?

Many cleaning products are alkaline because alkaline substances can help remove fats, oils, and grease.

For example, sodium hydroxide is used in some powerful drain and oven cleaners.

However, strong alkaline cleaners can also be corrosive, so they must be handled carefully.

Milder bases are found in soaps and other everyday cleaning products.

Antacids and Stomach Acid

Your stomach contains hydrochloric acid, which helps digest food and provides an environment where digestive enzymes can work effectively.

Sometimes excess stomach acid can cause discomfort.

Antacids contain bases that react with and neutralise some of this acid.

For example:

acid + base → salt + water

This is an everyday example of a neutralisation reaction.

Acidic, Neutral, or Basic?

We can classify aqueous substances according to their pH.

Pure water is approximately neutral at room temperature and has a pH close to 7.

It is important to remember that pH applies to aqueous solutions. We usually test a substance after it has dissolved or mixed with water.

Investigating Household Substances

We can investigate household substances using indicators.

A simple classroom investigation might test substances such as:

• lemon juice
• vinegar
• water
• baking soda solution
• soap solution
• diluted fruit juice

Universal indicator or pH paper can be used to estimate the pH.

Example Results

Actual results can vary depending on the product and its concentration.

Designing an Investigation

A good scientific investigation should use the same procedure for each substance.

For example:

Question: Which household substances are acidic, neutral, or alkaline?

Independent variable:
The household substance being tested.

Dependent variable:
The pH or indicator colour.

Controlled variables:

• volume of each sample
• amount of indicator
• type of indicator
• temperature
• method used to measure pH

Students could record their results and then arrange the substances from most acidic to most alkaline.

Using Natural Indicators

Some plants contain pigments that change colour depending on pH.

Red cabbage is a particularly useful natural indicator.

Red cabbage indicator typically becomes:

• red/pink in acidic solutions
• purple near neutral
• blue/green in alkaline solutions

This makes red cabbage indicator an excellent way to investigate acids and bases using relatively common materials.

Why Are Acids and Bases Important?

Acids and bases play important roles throughout daily life.

Food and Cooking

Acids affect the flavour, preservation, and chemical behaviour of foods.

Vinegar is used in pickling, while acids and bases can also react during baking.

Digestion

Hydrochloric acid in the stomach helps create the conditions required for digestion.

Bases in antacids can neutralise excess stomach acid.

Cleaning

Alkaline cleaners help remove grease, while some acidic cleaners are useful for removing mineral deposits.

Dental Health

Bacteria in the mouth can produce acids from sugars. These acids can attack tooth enamel.

Saliva helps control pH, while toothpaste can contain substances that help reduce the effects of acids.

Agriculture

The pH of soil affects how well plants can obtain nutrients.

Farmers may add materials such as calcium carbonate to acidic soils to raise the soil pH.

Swimming Pools and Aquariums

Water pH must often be monitored because organisms and chemical treatments work best within particular pH ranges.

Acids and Bases Can Be Useful and Dangerous

The words acid and base do not automatically mean dangerous.

Lemon juice is acidic, while baking soda is basic, yet both are commonly used in food.

However, concentrated acids and strong alkalis can be corrosive.

The danger depends on factors such as:

• the particular chemical
• its concentration
• the amount present
• how it is used

Household chemicals should therefore always be used according to their safety instructions.

Did You Know?

The pH scale is logarithmic.

This means a change of one pH unit represents a tenfold change in hydrogen ion concentration.

For example, a solution at pH 3 has 10 times the H⁺ concentration of a solution at pH 4 and 100 times the H⁺ concentration of a solution at pH 5.

So even apparently small differences in pH can represent significant chemical differences.

Key Terms

Acidic: Having a pH below 7.

Alkaline: Having a pH above 7.

Neutral: Having a pH of approximately 7.

Indicator: A substance that changes colour depending on pH.

pH: A measure related to the acidity or alkalinity of an aqueous solution.

Neutralisation: A reaction between an acid and a base.

Corrosive: Capable of chemically damaging materials or living tissue.

Key Takeaways

• Acids and bases are found in many everyday products.
• Lemon juice, vinegar, and many fruit juices are acidic.
• Baking soda solutions, soaps, antacids, and many cleaners are basic or alkaline.
• Aqueous substances can be classified using the pH scale.
• pH below 7 is acidic, pH 7 is neutral, and pH above 7 is alkaline.
• Indicators such as universal indicator, pH paper, and red cabbage indicator can be used to investigate household substances.
• Acids and bases are important in food, digestion, cleaning, agriculture, dental health, and water management.
• Strong or concentrated acids and bases can be hazardous and should always be handled carefully.