Introduction to Acids
So many of us have heard of the term pH, which in general is the measure of the amount of acidity or alkalinity that is in a solution. More specifically, it is a measure of the amount of protons or hydrogen ions that are present in an aqueous solution. Acids are primary contributors to the measure of pH in a solution, and the presence of acids a key characteristic of almost all solutions, from blood in the body to foods and drinks we consume. Let's discuss what an acid is and how it affects the pH of solutions when added.
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- 0:00 Introduction to Acids
- 0:34 How Acids Work
- 1:18 Weak vs. Strong Acids
- 2:32 Acids and the Human Body
- 3:00 Other Common Characteristics
- 3:18 Lesson Summary
How Acids Work
The pH scale is a scale that is used to represent the level of acidity in a solution. A solution with a pH of 7 is neutral, while a solution with a pH below 7 is an acid, and a solution with a pH above 7 is a base. An acid dissociates, or breaks apart, and donates protons, or hydrogen ions, in an aqueous solution, while a base donates hydroxide ions in a solution. Water, for example, is neutral with a pH of 7. When acids are added, they release more hydrogen ions into the solution, and this causes the pH of the solution to drop. Let me repeat: more hydrogen ions equals a lower pH and a more acidic solution.
Weak vs. Strong Acids
All acids will release hydrogen ions into solutions. The amount of ions that get released per molecule will determine if the acid is weak or strong. Weak acids are acids that partially release the hydrogen atoms that are attached. These acids, then, may lower pH by dissociation of hydrogen ions, but not completely. Weak acids include acetic acid, which is vinegar, and citric acid found in oranges and lemons.
Strong acids, on the other hand, completely dissociate and release ALL of their hydrogen atoms. This means that strong acids, in general, are more potent in lowering the pH of a solution. There are only 7 strong acids, including hydrochloric acid, which can be found in the stomach, and sulfuric acid, a corrosive acid found in things such as car batteries and fertilizers.
Many molecules can act as acids, even if they are not primarily used as acids. For example, adenosine triphosphate, or ATP, is a molecule used in the body for energy. But when added to a solution, ATP also releases hydrogen ions, which means it also can be considered an acid. Likewise, amino acids, which are the building blocks of proteins, will also release a small amount of hydrogen ions into aqueous solutions.
Acids and the Human Body
One of the coolest ways to look at acids is through their uses in the human body. Many of the processes that are present in the body require acids to maintain them. Examples include:
- Hydrochloric acid, which is produced in the stomach to assist with digestion.
- Fatty acids, which are released when the body breaks down fats for energy.
- Amino acids, which are used to make proteins within the body.
- Nucleic acids, which are responsible for our genetic make-up.
Other Common Characteristics of Acids
There are other common ways in which the characteristics of acids are experienced in everyday life, and in chemistry. For instance:
1) They change blue litmus paper red
2) They taste sour in aqueous solutions
3) They can form salts through reactions with some metals and bases
Acids are chemical agents that release hydrogen ions when added to water. The pH scale is used to show the acidity level of a given solution. When using the pH scale, more hydrogen ions equals a lower pH and a more acidic solution. Acids can be classified as weak or strong, depending on the amount of hydrogen ions that dissociate when the acid is placed in water. Acetic acid is an example of a weak acid, while hydrochloric acid, which is found in the stomach, is classified as a strong acid.
Acids also play many important roles in the human body, such as the building of proteins, which are made up of amino acids. Acids are a key characteristic of almost all solutions. This includes solutions that taste sour, the use of litmus paper to test for acidity, and acidic reactions that lead to the formation of salts.
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What is Acid in Chemistry? - Definition & Overview
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