Acids Bases and Salts

Acid, Base and Salt
Substances can be divided into three types – Acid, Base and Salt.
ACID: acids are substances that taste sour in nature. For example – lemon (citric acid), curd (lactic acid), vinegar (acetic acid), etc. The chemical nature of such substances is known as ACIDIC.
BASE: bases are substances which are soapy to touch and bitter in taste. For example; soap or soap solution, baking soda, washing soda, etc. The chemical nature of substances that contain base is known as BASIC.
INDICATOR: Indicator is a special substance that shows the acidic or basic nature of a substance by change in its colour. It is important to use indicators because some substances can be highly corrosive and can be very harmful to us if tasted.
Types of Indicator: Indicators can be divided into two types.
Natural Indicator: Indicators that are obtained from naturally occurring substance are called NATURAL INDICATORS. For example; litmus, turmeric, china rose, etc.
Synthetic Indicator: Indicators that are made in laboratory are called SYNTHETIC INDICATORS. For example; phenolphthalein, methyl orange, etc.
NATURAL INDICATORS:
Litmus: Litmus is extracted from Lichens.
Litmus is a purple coloured liquid in distilled water. it comes in the form of strips of two colours. One is called blue litmus paper and another is called red litmus paper.
Blue litmus paper turns into red when dipped in acidic solution.   Red litmus paper turns into blue when dipped in basic solution.
Turmeric: Turmeric is used as another natural indicator. It   is of yellow colour. Turmeric paper turns into red when it is dipped into basic solution. It does not change its colour with acid.
China Rose: China rose is another natural indicator. China rose solution gives dark pink (magenta) colour with acid and green colour with base.

Acid Rain: Carbon dioxide, sulphur dioxide and nitrogen dioxide which are released from vehicles and chimneys mix with droplets of rain and turn the rain water acidic. When...