Acids

1. Acids and Bases: Substances that ionise (break off) in an aqueous solution to produce hydrogen (H+) ions are known as acids, and the substances that ionise in an aqueous solution to produce hydroxide (OH-) ions are known as bases.
2. Neutralisation: The process where acids and bases neutralise each other to form salt and water is known as neutralisation. 
3. Salts: In chemistry, salts are products of the neutralisation reaction between an acid and a base. A salt is a compound composed of two ions, a positively charged ion and a negatively charged ion. The attraction between the two ions forms solid ionic bonds, giving salts a hard and brittle crystalline structure.

The term "acid" is derived from the Latin word "acidus," which means "sour." Many substances like lemon, tamarind, vinegar, and amla have a sour taste because they contain acids. Arrhenius was the first to describe acids and bases as substances that break apart, or ionise, in water to produce hydrogen ions (for acids) and hydroxide ions (for bases).

• Acids are compounds that are soluble in water and have a corrosive nature, meaning they can cause damage to certain materials.
• Both plants and animals contain acids. For example, citric acid in citrus fruits and acetic acid in vinegar are common.
• Natural or organic acids found in food are generally weak and safe to consume, such as tartaric acid in tamarind and lactic acid in yoghurt.
• Strong acids like sulphuric acid (H₂SO₄), hydrochloric acid (HCl), and nitric acid (HNO₃) are called mineral acids. These acids are caustic and can be dangerous to handle.
• To make strong acids less harmful, they are diluted by adding them slowly to water. This process must be done carefully, as it can still be hazardous.

Acid is categorised into 2 types

1. Organic Acid: Acids that come from organic sources like plants and animals. Examples include citric acid (found in citrus fruits), acetic acid (in vinegar), and oleic acid (from olive oil).
2. Mineral Acid: Acids are derived from minerals and known as inorganic acids. They do not contain carbon. Examples include H₂SO₄, HCl, and HNO₃.

Acid is categorised into 2 types

1. Oxy-acid: Acids that have oxygen in their composition, such as H₂SO₄ and HNO₃.
2. Hydracid: Acids are made up of hydrogen and other elements, but without oxygen. Examples include HCl, HI, and HBr.

The concentration of an acid depends on the number of hydrogen ions it releases in water. Acid is categorised into 2 types:

1. Concentrated Acid: An acid solution with a high percentage of acid mixed with water. Examples include concentrated hydrochloric acid, sulphuric acid, and nitric acid.
2. Diluted Acid: An acid solution with a low percentage of acid mixed with water. Examples include dilute hydrochloric acid, sulphuric acid, and nitric acid.