Acid and Alkali

I have learnt that Acids and Alkali have properties that differs from each other.

Acids
Acids are usually corrosive, sour in taste and turns moist blue litmus paper, red.
When acid reacts with reactive metal (Zinc, magnesium), hydrogen gas and chemical salt are produced. [Example, Zinc + Hydrochloric acid --> Hydrogen gas + Zinc Chloride]
Also, when acid reacts with metal carbonate ( Calcium carbonate, zinc carbonate), carbon dioxide, water and chemical salt will be produced. [Example, Zinc Carbonate + Hydrochloric acid --> Carbon Dioxide + Water + Zinc Chloride]

Alkali
Alkalis are also usually corrosive, have a soapy feel, taste bitter and it turns moist red litmus paper, blue.



Neutralization
Neutralization happens when an acid and alkali is mixed and it produces salt and water. [Example, Sodium Hydroxide + Hydrochloric Acid --> Sodium Chloride + Water]
When an Alkali is slowly added to an Acid solution, the pH level of the solution will increase. On the other hand, if an Acid is slowly added to an Alkali solution, the pH level of the solution will decrease.

Indicator

Indicators are used to tell if a solution is acidic or alkaline. A few examples of the common indicators are red/blue litmus paper, methyl orange, phenolphthalein and the universal indicator. Different indicators change solutions with different pH levels to different colours. 

        

Observing Neutralization using universal indicator

Colour change for different Indicators