SEBA Class 7 Science Chapter 3 Acidic Basic and Neutral Substances Found in Nature

SEBA Class 7 Science Chapter 3 Acidic Basic and Neutral Substances Found in Nature Solutions English Medium As Per SCERT New Syllabus to each chapter is provided in the list so that you can easily browse through different chapters SEBA Class 7 Science Chapter 3 Acidic Basic and Neutral Substances Found in Nature Notes and select need one. SEBA Class 7 Science Textual Notes Download PDF. SCERT Class 7 Science New Textbook Question Answer in English.

SEBA Class 7 Science Chapter 3 Acidic Basic and Neutral Substances Found in Nature

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Acidic Basic and Neutral Substances Found in Nature

Chapter: 3

PART – I

EXERCISES

1. Darken the circle for correct answer.

(i) You have dipped a red litmus paper into a solution and it turned blue. Which of the following solutions would turn it back to red?

(a) Baking soda.

(b) Vinegar.

(c) Lime water.

(d) Soap solution

Ans: (b) Vinegar.

(ii) Three unknown liquids were tested with different indicators: A turns red litmus to blue colour, B turns turmeric to red colour, C turns red rose extract to green colour. Which of the following is correctly matched?

(a) A-Acidic, B-Acidic, C-Acidic.

(b) A-Basic, B-Basic, C-Acidic.

(c) A-Basic, B-Basic, C-Basic.

(d) A-Neutral, B-Basic, C-Basic.

Ans: (c) A-Basic, B-Basic, C-Basic.

(iii) Which of the following natural indicator(s) will turn green when placed in a basic solution?

(a) Red rose extract.

(b) Turmeric.

(c) Purple cabbage.

(d) Litmus paper.

Ans: (a) Red rose extract.

(iv) A farmer finds that crops are not growing well because the soil is too acidic. Which of the followings should be added by him to neutralise the soil?

(a) Vinegar.

(b) slaked lime.

(c) Common salt.

(d) Lemon juice.

Ans: (b) slaked lime.

2. Riya was bitten by a red ant and her grandfather applied moist baking soda. Give the reason.

Ans: When an ant (or bee) stings, it injects formic acid into the skin, which causes pain and burning. Baking soda is a mild base, and applying it helps neutralise the acid, providing relief.

3. Match the indicator to its colour.

Indicator	In Acid	In Base
Red Litmus Paper
Turmeric Solution
Red Rose Extract

Ans: 

Indicator	In Acid	In Base
Red Litmus Paper	Red (No change)	Blue
Turmeric Solution	Yellow (No change)	Red / Reddish-brown
Red Rose Extract	Red	Green

4. Identify the colour. Ravi is given turmeric pasted paper and colourless liquid-soap water. What should he observe on the paper to identify the liquid?

Ans: He should observe the turmeric paper turning red. This is because soap water is basic, and turmeric acts as an indicator that turns red in the presence of a base.

5. You want to surprise your friend with a secret birthday message. The message should appear only when a special spray is used. Which natural solution can you use to write the message? Which natural indicator can you spray to reveal it? Can you design a fun experiment to try this?

Ans: Natural solution to write: I can use a basic solution like soap water or baking soda solution.

Natural indicator to spray: I can spray turmeric solution to reveal it.

Fun Experiment: I can apply a turmeric paste to a white paper and let it dry. Then I write my message using a cotton swab dipped in soap water. The message will appear in reddish-brown on the yellow paper. Alternatively, I can write with baking soda solution on white paper (invisible), and spray with red rose extract to reveal it in green.

6. A liquid solution turns blue butterfly pea extract green. What does it tell you about the liquid’s nature? What change would be there if you add elephant apple juice or vinegar to it?

Ans: The liquid is basic in nature. If you add elephant apple juice or vinegar (which are acidic), a neutralisation reaction will occur. The green colour will change as the base is neutralised, eventually turning the extract back to blue (neutral) or pinkish (acidic).

7. Complete the table.

Material Used to Write	Spray Solution	Visible Colour
Soap Water	Turmeric Solution
Vinegar	Red Cabbage Extract
Baking Soda	Red Rose Extract

Ans: 

Material Used to Write	Spray Solution	Visible Colour
Soap Water	Turmeric Solution	Reddish-brown
Vinegar	Red Cabbage Extract	Red / Pink
Baking Soda	Red Rose Extract	Green

8. After mixing grape juice with red rose extract, the solution turns reddish colour. What happens if baking soda is added to the above solution? Explain the reason.

Ans: The solution will turn green. Grape juice is acidic, which turns the red rose extract red. Adding baking soda (a base) neutralises the acid. Once the solution becomes basic, the red rose indicator changes its colour to green.