Properties of Acids and Bases - SS1 Chemistry Lesson Note

Acids and bases are two fundamental types of chemical substances that play a crucial role in chemistry, biology, and everyday life. Understanding their properties is essential for a wide range of applications, from chemical reactions and industrial processes to biological systems and environmental science. We will delve into the properties of acids and bases, exploring their characteristics and behaviours:

 

Acids:

Acids are substances that, when dissolved in water, release hydrogen ions (H+). They exhibit the following properties:

 

1. Sour Taste: Many acids have a sour taste, although it is important to note that tasting acids can be dangerous and is not recommended.

 

1. Corrosive: Acids can react with and corrode certain materials, including metals, due to their ability to donate hydrogen ions.

 

1. Turns Blue Litmus Paper Red: Acids can change the colour of blue litmus paper to red, indicating their acidic nature.

 

1. React with Bases: Acids react with bases to form salts and water in a process known as neutralisation. This reaction involves the transfer of protons (H+) from the acid to the base.

 

1. Conduct Electricity: Acids conduct electricity when dissolved in water or in an aqueous solution due to the presence of mobile ions (H+ and anions).

 

1. pH less than 7: Acids have a pH value lower than 7 on the pH scale, which is a logarithmic scale used to measure the acidity or alkalinity of a solution.

 

Bases:

Bases, also known as alkalis, are substances that, when dissolved in water, release hydroxide ions (OH-). They exhibit the following properties:

 

1. Bitter Taste: Many bases have a bitter taste, although, similar to acids, tasting bases is not recommended.

 

1. Slippery or Soapy Feel: Bases can feel slippery or soapy to the touch. This characteristic is commonly observed when handling substances such as sodium hydroxide (NaOH).

 

1. Turns Red Litmus Paper Blue: Bases change the colour of red litmus paper to blue, indicating their basic nature.

 

1. React with Acids: Bases react with acids in a neutralisation reaction, resulting in the formation of salts and water.

 

1. Conduct Electricity: Bases conduct electricity when dissolved in water or in an aqueous solution due to the presence of mobile ions (OH- and cations).

 

1. pH greater than 7: Bases have a pH value higher than 7 on the pH scale, indicating their alkaline nature.

 

Acid-Base Reactions:

Acid-base reactions involve the transfer of protons (H+) from the acid to the base. In these reactions, the acid donates a proton, while the base accepts it. The result is the formation of salt and water. This process is commonly referred to as neutralisation and is often used in various applications, such as in the production of pharmaceuticals, the treatment of acidic soils, and the balancing of pH in biological systems.

 

Strength of Acids and Bases:

Acids and bases can vary in their strength, which refers to their ability to donate or accept protons. Strong acids and bases completely dissociate in water, releasing a high concentration of H+ or OH- ions. Weak acids and bases, on the other hand, only partially dissociate, resulting in a lower concentration of H+ or OH- ions.

 

It is important to note that the properties of acids and bases can overlap and are not absolute. Some substances can exhibit acidic properties in certain conditions and basic properties in others.

 

 

Understanding the properties of acids and bases is crucial in various scientific disciplines:

-       Chemistry: The properties of acids and bases form the foundation of acid-base chemistry, including titrations, pH calculations, and understanding reaction mechanisms.

 

-       Biology and Biochemistry: Acids and bases play essential roles in biological systems, such as maintaining pH balance in cells, enzyme catalysis, and acid-base regulation in the body.

 

-       Environmental Science: Understanding the properties of acids and bases is vital in monitoring and assessing water and soil quality, as well as studying the impact of acid rain and pollution on ecosystems.

 

-       Industry and Manufacturing: Acids and bases are utilised in numerous industrial processes, including the production of chemicals, metals, and pharmaceuticals.