1. An acid, in chemistry, is usually a liquid, that contains hydrogen and has a pH value of less than 7. The hydrogen can be replaced by a metal to form a salt. The pH value of a base is always more than 7 and it usually combines with an acid to form a salt. A pH value is a scale to define the acidity or alkalinity of a substance.
2. acids are good conducturs of electricity as they have H+ ions while bases are not.
3. As regards physical properties, acids are sour in taste and can burn or destroy substances they come in contact with. They leave a stinging effect on mucous membranes. Bases, on the other hand, taste bitter and have a soapy or slippery texture.