CBSE Class 6th Solutions
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Ncert – Class 7th – Chapter 7th – Acids ,bases and salt

Ncert -Chapter 6th – Solution- Physical And Chemical Changes

In this post we will see  class 7th Science  – Physical And Chemical Changes based on NCERT. It can be used for all the students studying in CBSE boards or any board which are using the NCERT books for their syllabus. All the answers are prepared by Expert teachers and are very useful for all the board using NCERT like CBSE, State boards.

you can check Previous Chapter Solutions here –

Also Class 7th Science All chapters solutions here –

Exercise 1st – Answer In Brief 

[1] Name one example each of acidic basic and netural substance ?

Solution -[1] Acid = Lemon

[2]   Basic = Baking soda

[3] Netural = Salt

[2] What is an indicator ?

Solution – An indicator is an substance that change colour in the presence of an acid or base

[3] Name three substance that w use as indicator ?

Solution – Three substance that we use as indicator are Turmuru , Lithmus ,China rose .

[4] Does a neytralisation reaction always result in the formation of a netural salt ?

Solution – Yes ,a netratisation reaction always in the formation of netural salt .

[5] Why factory effluent harmful to aquitic animal ?

Solution – Factory effluent harmful to aquatic organisms because many factory effluent are acid in nature.

Exercise – 2nd Answer in long

[1] You are given three materials in the form and solution citric acid magnesium hydroxide and sodium sulphate ? Describe ?

Solution – Purple cabbage juice however change its colour from purple to red when it comes in contant with an acid and form purple to green with base . purple cabbage juice is thus an indicator for an acid as well as an base do not change colour with an indicator netural solution

[2] An acidic substance is mixed with an euilent amount of basic substance ?

Solution – [1] Salt ,water and heat is realsed

[2] Yes heat energy is realsed

[3] Netural

[3] Write a short note on strong and weak acid ?

Solution – Weak and strong acid ;-

All acid are not alike the naturally occuring acid are present in plants and animals and are called organic acid these are also weak acid such as Hydrochloric acid (hcl3)  Sulphric acid (H2SO4)  and nitric acid (HNO3) Which are commonly used in laborties are called mineral acid and strong acid .

[4] Describe the properties of bases name to base and their uses ?

Solution – Propertries of bases ;-

Bases like acid have a number of propertis that help us distinguish ;-

[1] Bases are bitter of taste .

[2] Bass feel soaphy and slippery to the touch .

[3] Bases react with acid to form a salt and water by neturalisation .

[4] Bases change blue lithmus paper to red .

Uses of bases

[1]Potassium hydroxide                                                           –    In alkaline Batteries

[2] Sodium hydroxide                                                               –   For manufacturing soaps and degertent

[5] Farmer sometime sprinkle while lime pouder in their feilds  ? How does it help 

Solution –  When excess chemical fertilsers are used in farming the soil becomes acidic to neturalises the acid farmers add base like quickline or slaked lime to the soil .

Exercise – 3rd Multiple choice question

[1] Which of the following are true about of acid ?

[1] Acid have  a sour taste .

[2] Acid turn red red lithmus blue .

[3] Acid turn purple cabbage juice red .

[4] Acid change the colour of turmeric to red .

Answer – Acid have a sour taste and acid change purple cabbage juice red    – [1] and [3] 

[2] Vinegar is ___________

{1] Netural                  [2]  Acidic                  [3] Basic             [4]  A salt

Answer – Acidic 

[3] Lime juice ___________

[1] Turns red lithmus to blue and turns purple cabbage juice to green and turns purple cabbage juice to green

[2] Has no effect on turmeric & turns blue litmus to red .

Answer – has no effeect on turmeric & turns blue litmus to red .

[4] A base _______________

[1] Has a bitter taste & turns red litmus blue

[2] turns purple cabbage juice red & has no effect on turmeric.

Answer – Has a bitter taste & turns red litmus blue.

[5] An acid does not cause any change in __________

[1] Red litmus & turmeric.

[2] Blue litmus & purple cabbage juice.

Answer – Red litmus & turmeric.

[6] Purple cabbage solution becomes ___________

[1] Red in an acid & green in a base

[2] Green in an acid & red in a base.

Answer – Red in an acid & green in a base

[7] Litmus paper turns ________

[1] Blue in a base & red in an acid.

[2] Blue in an acid & red in a base

Answer – Blue in a base & red in an acid.     

[8] Backing sod turns _________

[1] turmeric red

[2] purple cabbage juice green

[3] red litmus blue

[4] all of the above

Answer – All of the above

[9] A neutralisation reaction between a strong acid and a weak base forms _________

[1] An acidic salt

[2] A basic salt

[3] A netural salt

[4] Table salt

Answer – An acidic salt

[10] To neturlise the acid in soil farmer add ___________

[1] HCL

[2] CA(oh)2

[3] Naoh

[4] Nacl

Answer – CA (oh)2

Exercise – 4th Fill in the blanks 

[1] A sour fruit such as an orange or a lemon contain a weak _______ in it .   [ Acid]

[2] _________ acid is found in curd . [ Lictic]

[3] Sulphric acid and hydroloric acid are example  of _________ acid . [ Strong] 

[4] An __________ is a substance  which is used  to tell wheter a substance is acidic or base  .[ Indicator]

[5] A substance that does not change the colour of an indicator is called ___________ .   [ Netural ]

[6] Two natural indicator which can be used to detect basic substance are __________ and __________ . [ Purple & cabbage]

[7] An ant bite contains __________ acid . [ Formic] 

Exercise – True or false 

[1] The soda that we drink contains a base. [ false] 

[2] An acid can be made concrted by evaporating the watr from it .  [ True]

[3] strong acid can burn the skin as they are corrosive . [True]

[4] Red lithmus paper can be used to tell an acidic material from a netural materials  . [ False] 

[5] China rose solution turns blue when acid is added to it . [False] 

[6] The salt that is formed as the result of a nturalisation reaction between an acid and a base is always ntural . [ True]

[7] Antacids are made of acidic substance . [ False] 

you can check Previous Chapter Solutions here –

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Also Class 7th Science All chapters solutions here –

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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