The taste of Acid is Sour, that of Base is Bitter and salt is salty. So, Pickle and Lemons give sour taste due to presence of Acids. The sour taste of Lemon is due to presence of Citric Acid in it. While the sour taste of Pickle is due to presence of Vinegar (5% Acetic Acid Solution). Vinegar is mainly used to prevent the Pickle from Bacterial Attack.
Energy that comes from the heat of the Earth's core is known as geothermal energy. Solar energy comes from the Sun, hydro energy from water, and wave energy from wind and waves.
