Acids, Bases and Salts · Lesson 8 of 12
Importance Of pH In Everyday Life
“From stomach aches to tooth decay, pH has been quietly involved in everything.”
• Explain why living organisms require a suitable pH range. • Explain the effect of acid rain on aquatic life. • Describe how soil pH can affect plant growth. • Explain the role of antacids in the digestive system. • Explain tooth decay and sting relief using acid-base ideas.
pH is not just a laboratory measurement. Biological systems, soil, teeth, digestion and even defensive chemicals used by plants and animals depend on acidity and basicity.
Are Plants And Animals pH Sensitive?
Living organisms can function only within a limited pH range. Many biological reactions depend on enzymes and cellular processes that become disturbed when the environment becomes too acidic or too basic. The human body normally functions within a narrow range close to neutral.
Acid Rain is rainwater that becomes unusually acidic, with a pH below the stated natural threshold, due to acidic substances in the atmosphere.
When acidic rainwater enters rivers and lakes, it can lower the pH of the water. Aquatic organisms may not tolerate the change, making survival and reproduction difficult.
What Is The pH Of The Soil In Your Backyard?
Different plants grow best within different soil pH ranges. Soil can be mixed with water, shaken and filtered. The pH of the clear filtrate can then be tested using universal indicator paper.
If soil is too acidic, substances such as quicklime, slaked lime or chalk can be used to reduce acidity because they are basic in nature.
pH In Our Digestive System
The stomach produces hydrochloric acid, which supports digestion. Sometimes excess acid is produced and causes discomfort or irritation. Mild bases called antacids can neutralise some of the excess acid.
An Antacid is a mild basic substance used to neutralise excess acid in the stomach.
Magnesium hydroxide, commonly known as milk of magnesia, is a mild base that can be used as an antacid.
pH Change As The Cause Of Tooth Decay
Bacteria in the mouth break down sugars and food residues and produce acids. When the mouth becomes sufficiently acidic, tooth enamel begins to be attacked. Enamel contains calcium hydroxyapatite and is extremely hard, but prolonged acidic conditions can damage it.
Cleaning the mouth after eating removes food particles and reduces acid formation. Toothpastes are generally basic enough to help neutralise excess acid around the teeth.
Self Defence By Animals And Plants Through Chemical Warfare
A bee sting introduces an acidic substance that can cause pain and irritation. A mild base such as baking soda can help reduce the acidic effect.
Stinging hairs of nettle leaves can introduce methanoic acid into the skin. Traditional use of a nearby dock plant is presented as an example of natural neutralisation.
Quiz
Why can a mild basic antacid provide relief from excess stomach acid?
What can happen when acid rain lowers the pH of river water?
Which substance is commonly used as a mild antacid?
Why can basic toothpaste help reduce tooth decay?
Practice Problems
- Explain why large changes in pH can be harmful to living organisms.
- Explain how acid rain can affect aquatic organisms in rivers and lakes.
- Describe how soil pH can be tested and explain why it matters for plant growth.
- Explain how magnesium hydroxide can provide relief during excess stomach acidity.
- Explain how mouth bacteria, food residues and pH are connected with tooth decay.
Key Takeaways
• Living organisms function within limited pH ranges. • Acid rain can lower the pH of natural water and make survival difficult for aquatic organisms. • Soil pH influences healthy plant growth. • Antacids are mild bases that neutralise excess stomach acid. • Acidic conditions in the mouth can damage tooth enamel. • Acid-base neutralisation helps explain relief from some animal and plant stings.