hi mates,
can you please give me the summary of chapter 5 acids , bases and salt in class 7 NCERT book science. please give me immediately.
please but give in brief with explanation
and the condition is that you have to give this answer within 15 minutes
Answers
Answer:
Hope it will help you.
Explanation:
Notes Chapter 5 Acids, Bases and Salts
In our daily life, we use a large number of edible substances such as lemon, baking soda, tamarind, common salt, sugar, curd and vinegar. Some of these substances taste sour, some taste bitter, some taste sweet and some taste salty.
Acids, bases and salts are the three important groups of chemical substances that are used by us in different ways. Some of the acids, bases and salts occur in nature and they can be made artificially in factories also.
Edible substances and their tastes
SubstanceTaste (Sour/Bitter/Any other)Lemon JuiceSourOrange JuiceSourVinegarSourCurdSourTamarind(imli)SourSugarSweetCommon SaltSaltyAmlaSourBaking SodaBitterGrapesSweet/Sour
Acids and Bases
The word acid has been derived from a Latin word ‘acidus’ which means ‘sour’. Thus, all sour substances essentially contain acids. Substances like lemon juice, orange juice, unripe mango and curd taste sour. They taste sour because they contain substances called acids in them. The chemical nature of such substances is acidic. The acids in these substances are natural acids.
However, there are other substances like baking soda it does not taste sour.
It means that it has no acids in it. It is bitter in taste. And if prepare a solution of baking soda in water and rub it between your fingers, it feels soapy. Substance like these which are bitter in taste and feel soapy on touch are known as bases. The chemical nature of such substances is said to be basic. All the acids mentioned in table occur in nature.
Acids and their Sources
Name of AcidFound inAcetic AcidVinegarFormic AcidAnt’s StingCitric AcidCitrus fruits such as oranges, lemons, etc..Lactic AcidCurdOxalic AcidSpinachAscorbic Acid(Vitamin C)Amla, Citrus fruitsTartaric AcidTamarind, grapes, unripe mangoes, etc..
Bases and their Sources
Name of BaseFound inCalcium HydroxideLime WaterAmmonium HydroxideWindow CleanerSodium Hydroxide/Potassium HydroxideSoapMagnesium HydroxideMilk of Magnesia
Natural Indicators Around Us
It is not safe to taste every substance to find out if it is acidic or basic. There are some special substances that have different colours in acidic and basic mediums. These substances are known as indicators. The indicators change their colour when added to a solution containing an acidic or a basic substance.
Some naturally occurring indicators are litmus, turmeric, China rose petals (gudhal) and red cabbage juice. These indicators show different colours in acidic and basic media. They are used to test whether a substance is acidic or basic in nature.
Note: Phenolphthalein is an indicator used in the neutralisation process. When the solution is basic, phenolphthalein gives a pink colour but if the solution is acidic, it remains colourless.
Neutralisations in Everyday Life
The neutralisation reactions involving acids and bases play a very important role in our everyday life. The treatment of an ant’s sting, remedy for indigestion, soil treatment and the treatment of factory wastes, all involve neutralisation reaction.
Indigestion
Our stomach produces hydrochloric acid. This hydrochloric acid helps in digesting our food. Sometimes, excess of hydrochloric acid is produced in the stomach which causes indigestion. Due to indigestion, sometimes a person feels pain in the stomach and irritation. To relieve indigestion, we take an antacid such as milk of magnesia. Milk of magnesia contains a base called magnesium hydroxide. Magnesium hydroxide neutralises the excess acid present in the stomach and cures indigestion. Another antacid is baking soda which contains a base sodium hydrogen carbonate.
Ant Bite
When an ant bites, it injects an acidic liquid into the skin of the person which causes burning pain. The sting of an ant contains an acid called formic acid. The effect of the acid can be neutralised by rubbing a mild base like baking soda solution (sodium hydrogen carbonate) or calamine solution. Calamine solution contains a base called zinc carbonate. Thus, being a base, baking soda solution or calamine solution neutralises the acidic liquid injected by the ant and cancels its effect.
Soil Treatment
The soil may be acidic or basic naturally. The plants do not grow well, if the soil at a place is too acidic or too basic. Excessive use of chemical fertilisers makes the soil acidic. When the soil is too acidic, it is treated with bases like quicklime (calcium oxide) or slaked lime (calcium hydroxide). These bases neutralise the excess acid present in the soil and reduce its acidic nature. If the soil is basic, organic matter called manure or compost is added to it. The organic matter releases acids which neutralise the excess bases present in the soil and reduce its basic nature.
In our daily life, we use a large number of edible substances such as lemon, baking soda, tamarind, common salt, sugar, curd and vinegar. Some of these substances taste sour, some taste bitter, some taste sweet and some taste salty.
Acids, bases and salts are the three important groups of chemical substances that are used by us in different ways. Some of the acids, bases and salts occur in nature and they can be made artificially in factories also.Edible substances and their tastes
Substance Taste (Sour/Bitter/Any other)
Lemon Juice Sour
Orange Juice Sour
Vinegar Sour
Curd Sour
Tamarind(imli) Sour
Sugar Sweet
Common Salt Salty
Amla Sour
Baking Soda Bitter
Grapes Sweet/Sour
Acids and Bases
The word acid has been derived from a Latin word ‘acidus’ which means ‘sour’. Thus, all sour substances essentially contain acids. Substances like lemon juice, orange juice, unripe mango and curd taste sour. They taste sour because they contain substances called acids in them. The chemical nature of such substances is acidic. The acids in these substances are natural acids.
However, there are other substances like baking soda it does not taste sour.
It means that it has no acids in it. It is bitter in taste. And if prepare a solution of baking soda in water and rub it between your fingers, it feels soapy. Substance like these which are bitter in taste and feel soapy on touch are known as bases. The chemical nature of such substances is said to be basic. All the acids mentioned in table occur in nature.Acids and their Sources
Name of Acid Found in
Acetic Acid Vinegar
Formic Acid Ant’s Sting
Citric Acid Citrus fruits such as oranges, lemons, etc..
Lactic Acid Curd
Oxalic Acid Spinach
Ascorbic Acid(Vitamin C) Amla, Citrus fruits
Tartaric Acid Tamarind, grapes, unripe mangoes, etc..
Bases and their Sources
Name of Base Found in
Calcium Hydroxide Lime Water
Ammonium Hydroxide Window Cleaner
Sodium Hydroxide/Potassium Hydroxide Soap
Magnesium Hydroxide Milk of Magnesia
Natural Indicators Around Us
It is not safe to taste every substance to find out if it is acidic or basic. There are some special substances that have different colours in acidic and basic mediums. These substances are known as indicators. The indicators change their colour when added to a solution containing an acidic or a basic substance.
Some naturally occurring indicators are litmus, turmeric, China rose petals (gudhal) and red cabbage juice. These indicators show different colours in acidic and basic media. They are used to test whether a substance is acidic or basic in nature.