Science(Chap-5) Acids, Bases and Salts

Science(Chap-5)                                           Acids, Bases and Salts

Ø  Substances that we use in our day today life like lemon, tamarind, common salt, sugar,  vinegar etc.  tastes like sour, salty,  sweet and  bitter.

Ø  Curd, lemon juice, orange juice and vinegar etc. taste sour because these substances contain natural acids. The chemical nature of such substances is acidic.

Ø  The word ‘acid’ derived from the Latin word ‘acere’ which means sour.

Ø  Generally, substances which are bitter in taste and soapy to touch are known as ‘basics’.

Ø  We can not taste each and every substance. So, a special kind of substance known as ‘indicators’ are used to taste whether a substance is acidic or basic.

Ø  The substances change their colour when added to a solution containing an acidic or a basic substance. Turmeric, litmus, china rose petals etc. are some of the naturally occurring indicators.

·         Name of some Natural Acids found in different substances  of Nature:

Name of Acids	Found in
Acetic Acid	Vinegar
Formic Acid	Ant’s sting
Citric Acid	Citrus Fruits(Oranges, Lemons etc.)
Lactic Acid	Curd
Oxalic Acid	Spinach
Ascorbic Acid (Vitamin-C)	Amla, Citrus fruits
Tartaric Acid	Tamarind, Grapes, Unripe Mangoes etc.

·         Name of some  Basics found in different substances:

Name of Base	Found in
Calcium hydroxide	Lime water
Ammonium hydroxide	Window cleaner
Sodium hydroxide/ Potassium hydroxide	Soap
Magnesium hydroxide	Milk of magnesium

·         Natural Indicators:

Ø  The most commonly used natural indicator is litmus. It is extracted from lichens.

Ø  Litmus has a mauve(purple) colour in distilled water. When it is added to an acidic solution, it turns into red and when it is added to a basic solution it turns to blue.

Ø  Litmus is available in the form of a solution or in the form of paper stripes known as litmus paper.

Ø  The solutions which do not change the colour of either red or blue litmus are known as neutral solutions. These substances are neither acidic nor basic.

Ø  Litmus, turmeric and china rose  are some of the natural indicators through which we can test any substance to know whether it is acidic or basic.

·         Neutralization

Ø  We know that Acid turns Blue litmus Red and Bases turn Red litmus Blue. But when an acidic solution is mixed with a basic solution, both the solutions neutralize the effect of  each other,.

Ø  When  an acid solution and a base solution are mixed in suitable amounts, both the acidic nature of the acid and the basic nature of the base are destroyed. The resulting solution is neither acidic nor basic.

Ø  In neutralization reaction a new substance, salt is formed. Salt may be acidic, basic or neutral in nature.

Ø  The reaction between an acid and a base is known as neutralization. Salt and water is produced in this process with the evolution of heat. 

                      Acid + Base------Salt + Water (Heat is evolved)

 Hydrochloric Acid(HCl) + Sodium Hydroxide(NaOH)------Sodium Chloride(NaCL)+ Water(H2O)

Ø  Acid Rain: Rain containing excess of acids is known as acid rain. The rain becomes acidic because of carbon dioxide, sulphur dioxide and nitrogen dioxide (which are released into the air as pollutants)dissolve in rain drops to form carbonic acid, sulphuric acid and nitric acid respectively.

Neutralization in Everyday Life:

·         Indigestion in Human Body

Ø  Our stomach contains hydrochloric acid which helps to digest food. But too much of it in stomach causes indigestion and more acidic which is very painful.

Ø  To relieve from indigestion we take an antacid such as milk of magnesia(containing magnesium hydrochloride) which neutralizes the effect of excessive acid.

·         Ant bite :

Ø  When an ant bites, it injects the acidic liquid namely, formic acid into the skin. The effect of the acid can be neutralized by robbing moist baking soda(sodium hydrogencarbonate) or calamine solution, which contains zinc solution.

·         Soil Treatment:

Ø  Excessive use of chemical fertilizers makes the soil acidic. Plants can not grow well when the soil is either too acidic or too basic.

Ø  When the soil is too acidic, it is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide).

Ø  when the soil is too basic, organic matter like compost is added to it. Organic matter releases acids which neutralizes the basic nature of the soil.

·         Factory Wastes:

Ø  The factory wastes contain acids, when it is flowed into the water bodies, the acids kill the fish and other organisms. The factory wastes are, therefore, neutralized by adding basic substances.

https://kahoot.it/challenge/03762655?challenge-id=5ac596f0-3bc2-42c7-aa21-764afaa1cae4_1589549847225