Notes of Ch 2 Acids, Bases and Salts: Class 10th Science Introduction The sour and bitter tastes of food are due to acids and bases are present in them. Acids are sour in taste and change the colour of blue litmus to red. Litmus solution is a purple dye, which is extracted from lichen. When the litmus solution is neither acidic nor basic, its colour is purple. Other natural materials like red cabbage leaves, turmeric, coloured petals of some flowers such as Hydrangea, Petunia and Geranium, which indicate the presence of acid or base in a solution. Properties of Acids They release H + ions in aqueous solution. Acids have sour taste. They turn blue litmus solution red. They give H + ions in aqueous solution. Strong Acids: HCl, H 2 SO 4 , HNO 3 Weak Acids: CH 3 COOH, Oxalic acid, Lactic acid Concentrated Acids: More amount of acid + Less amount of water Dilute Acids: More amount of water + Less amount of acid Properties of Bases They have a bitter taste. They are soapy to t