Exploring Substances: Acidic, Basic, and Neutral Class 7 (Curiosity)

Q1 (Medium): A solution turns the red litmus paper to blue. Excess addition of which of the following solution would reverse the change? (i) Lime water (ii) Baking soda (iii) Vinegar (iv) Common salt solution

Q2 (Medium): You are provided with three unknown solutions labelled A, B, and C, but you do not know which of these are acidic, basic, or neutral. Upon adding a few drops of red litmus solution to solution A, it turns blue. When a few drops of turmeric solution are added to solution B, it turns red. Finally, after adding a few drops of red rose extract to solution C, it turns green. Based on the observations, which of the following is the correct sequence for the nature of solutions A, B, and C?

Q3 (Easy): Observe and analyse Figs. 2.13, 2.14, and 2.15, in which red rose extract paper strips are used. Label the nature of solutions present in each of the containers.

Q4 (Medium): A liquid sample from the laboratory was tested using various indicators: Red litmus - No change; Blue litmus - Turned red; Turmeric - No change. Based on the tests, identify the acidic or basic nature of the liquid and justify your answer.

Q5 (Medium): Manya is blindfolded. She is given two unknown solutions to test and determine whether they are acidic or basic. Which indicator should Manya use to test the solutions and why?

Q6 (Difficult): Could you suggest various materials which can be used for writing the message on the white sheet of paper and what could be in the spray bottle? Make a table of various possible combinations and the colour of the writing obtained.

Q7 (Medium): Grape juice was mixed with red rose extract; the mixture got a tint of red colour. What will happen if baking soda is added to this mixture? Justify your answer.

Q8 (Medium): Keerthi wrote a secret message to her grandmother on her birthday using orange juice. Can you assist her grandmother in revealing the message? Which indicator would you use to make it visible?

Q9 (Easy): How can natural indicators be prepared? Explain by giving an example.

Q10 (Medium): Three liquids are given to you. One is vinegar, another is a baking soda solution, and the third is a sugar solution. Can you identify them only using turmeric paper? Explain.

Q11 (Medium): The extract of red rose turns the liquid X to green. What will the nature of liquid X be? What will happen when excess of amla juice is added to liquid X?

Q12 (Medium): Observe and analyse the information given in the following flowchart. Complete the missing information. Imagine a garden with plants showing signs of poor health. The soil can be ______ in nature. Which indicator can be used to test the nature of the soil? The acidic soil can be treated with ____. The basic soil can be treated with ____.

Property
Acids
Bases
Litmus test
Turn blue litmus red
Turn red litmus blue
Red rose extract
Gives red colour
Gives green colour
Turmeric paper
No colour change
Turns red
Taste
Sour taste
Bitter taste
Touch
Normal
Slippery to touch
Neutralisation Process
General Reaction
Acid
+
Base
→
Salt
+
Water
+
Heat
Ant Bite Treatment
Formic Acid
+
Baking Soda
→
Salt
+
Water
Soil Treatment
Acidic Soil
+
Lime
→
Neutral Soil