CBSE Class 10 Answered

PHYSICAL PROPERTIES OF ACIDS: 
1. Acids have a SOUR taste 
2. All acids are SOLUBLE in water 
3. Acids solutions turn BLUE litmus paper RED 
4. Acid solutions have a pH values < 7 
5. Most acid solutions are CORROSIVE 
6. All dilute acids CONDUCT ELECTRICITY due to the presence MOBILE IONS in solution 
7. React with reactive metals (above H in Reactivity Series) to form Salt & Hydrogen Gas 
8. React with Metal Carbonates to form Salt, Carbon Dioxide & Water 
9. React with Bases/Alkali to form Salt & Water Neutralisation Reaction) 
empirical definition of acids: acids are aqueous solutions that have a sour taste, a pH higher than 7 and are conductive. 

A base is most commonly thought of as an aqueous substance that can accept H⁺ ions. 

Bases are usually oxides and hydroxides of metals. Bases that dissolve in water are called alkalis. They have the following properties:

1. Bases are bitter to taste and soapy to touch.

2. Bases turn red litmus paper blue.

3. Bases are characterised by the presence of hydroxyl (-OH) group.

4. Bases react with acids to form salt (a neutral substance) and water.

5. Bases are corrosive to skin; they should not be touched by hand.