Acids, basis and salts
NCERT solutions for Science Acids, basis and salts
NCERT Class 7 Social Science Chapter wise Solutions
- Nutrition in Plants
- Nutrition in Animals
- Fibre To Fabric
- Heat
- Acids Bases And Salts
- Physical And Chemical Changes
- Climate
- Winds Storms And Cyclones
- Soil
- Respiration In Organisms
- Transportation in Animals And Plants
- Reproduction In Plants
- Motion And Time
- Electric Current And Its Effects
- Light
- Water
- Forests: Our Lifeline
- Waste Water Story
NCERT solutions for Class 7 Science Acids, basis and salts
Class–VII (CHAPTER-05)
ACIDS, BASES AND SALTS
Question 1.State differences between acids and bases.
Answer:
Acids are sour and turn blue litmus red. Bases are bitter and turn red litmus blue.
Question 2.Ammonium is found in many household products, such as window cleaners. Itturns red litmus blue. What is its nature?
Answer:
Basic
NCERT solutions for Class 7 Science Acids, basis and salts
Question 3.Name the source from which litmus solution is obtained. What is the use of thissolution?
Answer:
Lichens. It is used as indicator.
Question 4.Is the distilled water acidic/basic/neutral? How would you verify it?
Answer:
Distilled water is neutral.
Question 5.Describe the process of neutralization with the help of an example.
Answer:
The reaction between an acid and a base is known as neutralization. Salts and water are produced in this process with the evolution of heat.
Acids + Bases -à Salt + water
HCl + NaOHàNaCl + H2O.
NCERT solutions for Class 7 Science Acids, basis and salts
Question 6.Mark ‘T’ if the statement is true and ‘F’ if it is false.
(i) Nitric acid turns blue litmus red. (T/F)
(ii) Sodium hydroxide turns blue litmus red. (T/F)
(iii) Sodium hydroxide and hydrochloric acid neutralize each other and forms salts andwater. (T/F)
(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)
(v) Tooth decay is caused by the presence of a base. (T/F)
Answer:
(i) F
(ii) F
(iii) T
(iv) T
(v) F
Question 7.Dorji has a few bottles of soft drink in his restaurant, but, unfortunately theseare not labelled. He has to serve the drinks on the demand of customers. One customerwants acidic drink; another wants basic and third one wants neutral drink. How will Dorjidecide which drink it to be served to whom?
Answer:
He can decide by the use of indicator. If the sample of drink turns red litmus blue, it isbasic. If it does not turn blue litmus red, it is acidic. If it does not affect litmus, it is neutral.
Question 8.Explain why:
(a) An antacid tablet is taken when you suffer from acidity.
(b) Calamine solution is applied on the skin when ant bites.
(c) Factory waste is neutralized before disposing it into the water bodies.
Answer:
(a) Antacids are nothing but bases. When there is excess of acid in stomach, antacids aretaken. Antacids neutralize the acids and relieve us.
(b) Ant injects an acid during bite which causes the burning sensation. Calamine solution isbasic in nature. It neutralizes the acid and relieves from the pain.
(c) Factory wastes contain both acidic and basic substances. These are harmful for theorganisms living in water. So, these are neutralized.
NCERT solutions for Class 7 Science Acids, basis and salts
Question 9.Three liquids are given to you. One is hydrochloric acid, another is sodiumhydroxide and third is a sugar solution. How will you identify them? You have onlyturmeric indicator.
Answer:
Turmeric solution turns red in contact with bases. It is not affected by acids and neutralsubstances.
At first we will identify the base.
The base is taken and turmeric is added. It will turn red. Then, one of the solution is added to it gradually. If the solution turns yellow again, the added liquid is Hydrochloric acid. Otherwise the added liquid is sugar solution.
Question 10.Blue litmus paper is dipped in a solution. It remains blue. What is the nature ofthe solution? Explain.
Answer:
The solution may be neutral or basic. Both types of substance have no effect on blue litmus.
NCERT solutions for Class 7 Science Acids, basis and salts
Question 11.Consider the following statements:
(a) Both acids and bases change colour at all indicators.
(b) If an indicator gives a colour change with an acid, it does not give a change with abase.
(c) If an indicator changes colour with a base, it does not change colour with an acid.
(d) Change of colour in an acid and a base depends on the type of the indicator.
Which of these statements are correct?
(i)All four
(ii) a and b
(iii) b and c
(iv) only d.
Answer:
(iv) only d.