Exploring Substances Acidic Basic and Neutral Class 7 MCQ
hardExploring Substances Acidic Basic and Neutral Class 7 MCQ
Exploring Substances Acidic Basic and Neutral Class 7 MCQ
Question 1.
What substance is commonly used to relieve pain from ant bites?
(a) Lemon juice
(b) Baking soda
(c) Vinegar
(d) Water
Answer:
(b) Baking soda
Explanation: When an ant bites, it injects formic acid into the skin, causing red skin with stinging pain. By rubbing the moist baking soda on the red skin neutralise the acid, providing relief from the pain.
Question 2.
If a farmer discovers that his soil is too acidic and his plants are not growing well, which of the following substances can he use to treat the soil?
(a) Vinegar
(b) Lime
(c) Sugar
(d) Salt
Answer:
(b) Lime
Explanation: Lime is a basic substance that can be added to acidic soil to neutralise it. The acidic soil reacts with base and form salt and water, remove the acidity of soil.
Question 3.
Which natural indicator would turn red in the presence of an acidic solution like lemon juice?
(a) Turmeric
(b) Red cabbage extract
(c) Baking soda solution
(d) Sugar solution
Answer:
(b) Red cabbage extract
Explanation: Solution of lemon juice is acidic in nature. Red cabbage extract is a natural indicator, which turns acidic substances into red.
Question 4.
What is the result of mixing an acid with a base in a neutralisation reaction?
(a) Salt and water
(b) Only water
(c) Only salt
(d) Gas and liquid
Answer:
(a) Salt and water
Explanation: In a neutralisation reaction, an acid reacts with a base to produce salt and water, along with the release of heat.
Question 5.
What happens when baking soda is mixed with vinegar?
(a) No reaction occurs
(b) Neutral solution will be formed
(c) The solution turns blue
(d) The solution becomes solid
Answer:
(b) Neutral solution will be formed
Explanation: When baking soda (a base) is mixed with vinegar (an acid), they react with each other and form salt, water and heat. Salt solution is a neutral solution.
Question 6.
Which of the following substances turns blue litmus paper red?
(a) Soap solution
(b) Lemon juice
(c) Baking soda
(d) Salt solution
Answer:
(b) Lemon juice
Question 7.
Which of the following substances turns red litmus paper blue?
(a) Vinegar
(b) Lime water
(c) Soap solution
(d) Sugar solution
Answer:
(b) Lime water
Question 8.
What is the nature of tap water based on litmus test?
(a) Acidic
(b) Basic
(c) Neutral
(d) May be both, acidic or basic
Answer:
(c) Neutral
Question 9.
Which of the following is a natural acid-base indicator?
(a) Turmeric
(b) Vinegar
(c) Baking soda
(d) Salt
Answer:
(a) Turmeric
Question 10.
What colour does turmeric paper turn in a basic solution?
(a) Yellow
(b) Red
(c) Green
(d) Blue
Answer:
(b) Red
Case Study
I. The Lemonade Stand
Riya set up a lemonade stand on a hot summer day. She noticed that the lemon juice she used turned blue litmus paper red. Curious, she tested the same juice with turmeric paste, but there was no colour change. Later, she accidentally spilled some soap water into the lemon juice and observed fizzing.
Question 1.
What does lemon juice do to blue litmus paper?
(a) Turns it blue
(b) Turns it red
(c) No change
(d) Turns it green
Answer:
(b) Turns it red
Question 2.
What caused fizzing when mixed with lemon juice?
(a) Vinegar
(b) Salt
(c) Soap water
(d) Sugar
Answer:
(c) Soap water
Question 3.
Turmeric paste shows ............change with lemon juice.
Answer:
no
Question 4.
Soap water mixed with lemon juice produced .............
Answer:
fizz
Question 5.
Turmeric changes colour in acidic lemon juice. (True/False)
Answer:
False.
II. The Mysterious Three Liquids
Aman was given three colourless liquids labelled A, B, and C. He added red litmus to A and it turned blue. Turmeric turned red in B. Red rose extract turned green in C. He concluded that all three were basic.
Question 1.
Which liquid turned red litmus blue?
(a) A
(b) B
(c) C
(d) B and C both
Answer:
(a) A
Question 2.
What did red rose extract turning green in $\mathbf{C}$ indicate?
(a) Acidic nature
(b) Basic nature
(c) Neutral nature
(d) Salty nature
Answer:
(b) Basic nature
Question 3.
Turmeric turned ............in liquid B.
Answer:
red
Question 4.
Aman concluded that all three liquids were .............
Answer:
basic
Question 5.
Red litmus turning blue means the liquid is acidic. (True/False)
Answer:
False
III. The School Science Fair
At the science fair, a group of students demonstrated how red cabbage juice can be used as a natural indicator. They tested vinegar, soap solution, and salt water. The juice turned purple/pink with vinegar, green with soap, and remained unchanged with salt water.
(a) What is the nature of vinegar?
Answer:
Acidic
(b) Which solution was neutral in nature?
Answer:
Salt water
(c) How does red cabbage juice act as an indicator? Explain with examples.
Answer:
Red cabbage juice shows different colours in acidic and basic solution, so it acts as an indicator.
Red cabbage juice colour turns pink in acids (like vinegar), green in bases (like soap), and shows no change in neutral substances (like salt water).