BASIC in nature.A stain of curry on a white cloth BECOMES reddish-brown when soap is used because the soap is Basic in nature.A pH value is greater than 7 is basic in nature. Examples are Ca(OH)2, NAOH, NaHCO3.Bases turn red litmus to blue.Bases also react with some metals to liberate hydrogen gas.Oxides and hydroxides of metals are bases.WATER-soluble bases are called alkali. Example NaOH, KOHAll alkalies are bases but all bases are not alkalies because all bases are not soluble in water.Alkaline gives off OH- ions in water. AcidThe sour taste of organic food materials is mainly caused by the presence of acidic materials.Acids are sour in taste with a pH of less than 7. Examples are Vinegar, Tartaric acid, Citric acid, and Malic acid.Acids give off H+ ions in water.Acids turn blue litmus to red.NeutralizationAcid and base react together to form salt and water and this reaction is known as neutralization.Water is neutral with a pH value equal to 7.