Exploring Substances Acidic Basic and Neutral Class 7 Extra Questions and Answers Science Chapter 2

Students can keep Class 7 Science Extra Questions and Class 7th Curiosity Chapter 2 Exploring Substances Acidic Basic and Neutral Class 7 Important Extra Question Answer handy for quick reference during exams.

Class 7 Science Chapter 2 Exploring Substances Acidic Basic and Neutral Extra Questions

Class 7 Science Chapter 2 Extra Questions on Exploring Substances Acidic Basic and Neutral

Exploring Substances Acidic Basic and Neutral Class 7 Very Short Question Answer

Question 1.
What are acids?
Answer:
The substances which are sour in taste are called acids.

Question 2.
Name two substances that are acidic in nature.
Answer:
Lemon and tamarind

Question 3.
What are bases?
Answer:
The substances that feel soapy to touch and bitter in taste are called bases.

Question 4.
Which indicators change odour with different substances?
Answer:
Olfactory indicators

Question 5.
From which plant is litmus extracted?
Answer:
Lichens

Question 6.
What is the effect of acid and base on litmus?
Answer:
Acid converts blue litmus into red, while base converts red litmus into blue.

Question 7.
What are neutral substances?
Answer:
The substances which do not show any effect on litmus are called neutral substances.

Question 8.
Why does a turmeric stain red on a white shirt when it is washed with soap?
Answer:
It is because the soap solution is basic, and turmeric acts as a natural indicator that turns red in a basic solution.

Question 9.
Dip some crushed red rose petals in warm water to make the extract. Add a few drops of an acid and a base separately in two different containers. Write the effect of it on acid and base.
Answer:
Red rose petals extract turns red in an acidic solution and green in a basic solution.

Question 10.
Form a sentence using the following words – baking soda, ant bite, moist, effect, neutralised, rubbing. (NCERT Exemplar)
Answer:
The effect of an ant bite can be neutralised by rubbing moist baking soda.

Exploring Substances Acidic Basic and Neutral Class 7 Short Question Answer

Question 1.
What are indicators? Classify them and give one example of each.
Answer:
The substances which are used to test whether a substance is acidic or basic are called indicators.
There are two types of indicators:
(i) Natural indicators : Litmus paper, turmeric, etc.
(ii) Synthetic indicators : Phenolphthalein

Question 2.
What is litmus? How is it prepared?
Answer:
The most commonly used natural indicator is litmus. It is extracted from lichens. It is available in the form of a solution or strips of paper.

Question 3.
How do you prepare lime water?
Answer:
To prepare lime water, dissolve some lime (calcium oxide, also known as chuna) in water. Stir the mixture and let it sit for a while. Afterward, filter the solution, and the liquid obtained is lime water.

Question 4.
How can you prepare turmeric paper?
Answer:
Take some turmeric powder and mix it in some water to make a paste. Deposit it on blotting paper or filter paper and dry it. Cut thin strips of the yellow paper obtained. These thin strips are turmeric paper.

Question 5.
Explain the use of rose petals as indicators.
Answer:
Rose petals, when added to warm water, form an extract which is used as an indicator. This indicator turns red in an acidic solution and green in a basic solution.

Question 6.
What is a neutralisation reaction? Explain with an example.
Answer:
The reaction between an acid and a base is known as a neutralisation reaction. Salt and water are produced in this process along with the evolution of heat.
Acid + Base → Salt + Water (Heat is evolved.)

Question 7.
Blue litmus paper is dipped in a solution. It remains blue. What is the nature of the solution? Explain.
Answer:
(i) It can be identified on the basis of the following observations: Bases change the colour of Red litmus paper to blue. As the colour of blue litmus paper is not affected, the solution must be basic.

(ii) If the solution is neutral, even then the colour of litmus will not change. Hence, the solution may be basic or neutral.

Question 8.
While playing in a park, a child was stung by a wasp. Some elders suggested applying a paste of baking soda, and others lemon juice as a remedy. Which remedy do you think is appropriate and why?
Answer:
A wasp bite injects base into the body. The effect of the injected base can be nullified by applying acid to the infected area. Therefore, it is advisable to apply lemon juice to the affected area because it is an acid.

Exploring Substances Acidic Basic and Neutral Class 7 Long Question Answer

Question 1.
What are acids and bases? Explain their properties with examples.
Answer:
Acids and bases are two types of substances with different properties. Acids are substances that taste sour and turn blue litmus paper red. They can be strong or weak. Some common acids are lemon juice (contains citric acid), vinegar (contains acetic acid), curd (contains lactic acid), and tamarind (contains tartaric acid). Bases are substances that taste bitter and feel soapy to touch. They turn red litmus paper blue. Bases can also be strong or weak. Some common bases are soap, baking soda, and lime water.

Question 2.
What is neutralisation? Give examples of neutralisation in daily life.
Answer:
The reaction between an acid and a base is called neutralisation. In this reaction, a salt and water are formed, and heat is also released.
Acid + Base → Salt + Water + Heat Neutralisation in daily life:
The sting of an ant contains formic acid, which causes pain and irritation. When we apply moist baking soda (a base), it neutralises the acid and gives relief. When soil becomes too acidic, plants cannot grow well. Farmers add lime (calcium oxide), which is a base, to neutralise the acid in the soil. If the soil is too basic, they add organic matter (compost) to make it neutral. Wastes from factories are often acidic. If this acidic water is released into rivers or lakes, it can harm plants and animals. So, before releasing it, factories add basic substances to neutralise the acids.

Question 3.
You are given a number of substances. Write the taste of these substances and complete the table.

Answer:

Question 4.
You are provided with four test tubes containing sugar solution, baking soda solution, tamarind solution, salt solution. Write down an activity to find the nature (acidic/ basic/ neutral) of each solution.
Answer:
This can be identified using litmus paper. If blue litmus changes to red, the solution is acidic. If red litmus changes to
blue the solution is basic. If there is no change in colour of the litmus paper, then the solution is neutral.

Exploring Substances Acidic Basic and Neutral Class 7 Skill Based Questions

Question 1.
(a) Draw a diagram to show the preparation of a greeting card using turmeric paste and soap solution.
(b) What is the effect of soap solution on turmeric paste?
Answer:
(a) Turmeric paste Soap solution
(b) The soap solution turns yellow turmeric paste into red.

Question 2.
Predict the colour change when red rose extract is added to vinegar and baking soda solution.
Answer:
Vinegar (acidic) → Red rose extract turns red.
Baking soda (basic) → Red rose extract turns green.

Exploring Substances Acidic Basic and Neutral Class 7 Case Based Questions

I. Anjali’s mother was planting flowers in the garden. She noticed that the Hydrangea plant in one pot had blue flowers, while the one in another pot had pink flowers. Anjali was surprised and asked her mother about it. Her mother told her that the colour of Hydrangea flowers changes depending on the nature of the soil.
Question 1.
What kind of soil turns Hydrangea flowers blue?
Answer:
Acidic soil turns Hydrangea flowers blue.

Question 2.
What does pink colour in Hydrangea indicate about the soil?
Answer:
It means the soil is basic in nature.

Question 3.
What type of substance is present in the soil if it is acidic?
Answer:
The soil contains acidic substances.

OR
Name one reason why Hydrangea changes its flower colour.
Answer:
Hydrangea changes colour because the nature of the soil (acidic or basic) affects how it absorbs nutrients.

Exploring Substances Acidic Basic and Neutral Class 7 Suggested Projects and Activities

1. Make a creative design or pattern on paper (like a rangoli) by using natural indicators such as turmeric, hibiscus or red cabbage juice. Then, use acidic and basic substances like lemon juice, soap solution or baking soda solution to develop colours and patterns. Observe how the colours change based on the nature (acidic or basic) of the substances.

2. Collect a soil sample from your school playground, garden or any nearby area. Mix it with distilled water and use a natural indicator like turmeric or red cabbage extract to test its acidity or basicity. Observe any colour changes and identify whether the soil is acidic, basic or neutral. Discuss how this affects plant growth in your area.

Class 7 The Ever Evolving World of Science Extra Questions for Practice

Question 1.
‘Litmus’, a natural dye is an extract of which of the following?
(a) Red hibiscus
(b) Lichen
(c) Beetroot
(d) Purple cabbage

Question 2.
When the soil is too acidic, plants do not grow well in it. To improve its quality what must be added to the soil?
(a) Organic matter
(b) Lime
(c) Manure
(d) Composted leaves

Question 3.
In acidic soil, Hydrangea flowers turn
(a) Red
(b) Pink
(c) Blue
(d) Yellow

Question 4.
Read the given statements and select the correct option.
Assertion (A): Onion is an example of olfactory indicator.
Reason (R): Onion changes its odour in acidic or basic medium.
(a) Both A and R are true and R is the correct explanation of A.
(fa) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

5. Match the items in Column A to those in Column B:

(a) (i)-(s), (ii)-(p), (iii)-(g), (iv)-(r)
(b) (i)-(s), (ii)-(r), (iii)-(p), (iv)-(q)
(c) (i)-(r), (ii)-(s), (iii)-(p), (iv)-(q)
(d) (i)-(s), (ii)-(p), (iii)-(r), (iv)-(q)

II. Very Short Answer Type Questions (1 mark each)

Question 6.
What is the nature of common salt?

Question 7.
Why does a turmeric stain on a white shirt turn red when it is washed with soap?

Question 8.
What is the effect of acids and bases on various types of litmus?

Question 9.
Name two substances that are basic in nature.

Question 10.
Write the chemical nature of soap.

III. Short Answer Type-1 Questions

Question 11.
What are natural indicators? Explain with the help of examples.

Question 12.
How is litmus prepared from the lichens?

Question 13.
What are neutralisation reactions? Explain with one example.

Question 14.
Explain the method of preparation of a greeting card using turmeric paste.

Question 15.
Write two differences between an acid and a base.

IV. Short Answer Type-2 questions

Question 16.
Fill in the blanks:
(i) The taste of an acid is ______ .
(ii) ______ is used in acidic soil.
(iii) The reaction between acid and base is called ______ .

Question 17.
Write true or false against the following statements:
(i) Sting of an ant contains vinegar.
(ii) A compound if acidic will turn all indicators red. .
(iii) Common salt turns blue litmus red.

Question 18.
Write two properties of an acid.

Question 19.
What do you mean by soil treatment?

Question 20.
What are indicators? Name two natural indicators.

V. Long Answer Type Questions

Question 21.
Explain the neutralisation process with the help of an activity.

Question 22.
Explain the effect of turmeric solution on: lemon juice, orange juice, vinegar, lime water and common salt.

Question 23.
How can the acidic nature of factory waste be neutralised?

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