AP State Syllabus AP Board 7th Class Science Solutions Chapter 2 Acids and Bases Textbook Questions and Answers.

AP State Syllabus 7th Class Science Solutions 2nd Lesson Acids and Bases

7th Class Science 2nd Lesson Acids and Bases Textbook Questions and Answers

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Question 1.
The sting of a wasp is basic. How can we treat the sting of a wasp?
Answer:

  1. The sting of wasp is basic. So it should be treated with an acid to neutralize it.
  2. Acetic acid may be taken and rubbed on the place where wasp put its sting.

Question 2.
Why are acids not stored in a metal container?
Answer:

  1. Acids react with metals releasing hydrogen.
  2. To avoid this acids are not stored in metal containers.

AP Board 7th Class Science Solutions Chapter 2 Acids and Bases

Question 3.
Acidic, basic and neutral solutions are given in three test tubes and you are given a strip of red litmus. How will you identify the three solutions?
Answer:

  1. Red litmus strip is dipped in the solutions contained in the three test tubes one after another.
  2. The solution in which red litmus is turned into blue is considered as base.
  3. The solution in which this blue litmus is turned into red is considered as an acid.
  4. The solution in which either red or blue litmus does not change its colour is neutral solution.

Question 4.
When drops of lemon juice are put on blue litmus it turns red, what will happen if you put some drops of soap solution on the same position on litmus paper?
Answer:

  1. Lemon juice is acidic. So blue litmus turned into red when drops of this juice are put on blue litmus.
  2. Soap solution is basic in nature. So when drops of soap solution are put on the same position of the litmus paper, the litmus paper slowly changes into blue colour.

Question 5.
What happens when Nitric acid is added to egg shell?
Answer:
When Nitric acid is added to egg shell carbon dioxide gas is released.

Question 6.
Turmeric stains on white clothes, when washed with soap, turn red. Why?
Answer:

  1. Turmeric is a natural indicator.
  2. It turns red when soap water is put in touch with it.
  3. So turmeric stains on white clothes, when washed with soap, turn red.

Question 7.
Ammonia is present in window cleaners. It turns red litmus blue. What is its nature?
Answer:
Ammonia has basic nature.

Question 8.
What is the nature of urea? Is it acidic / basic / neutral? How can we verify it? Urea is basic in nature. It turns red litmus to blue litmus.
Answer:
Red litmus paper is dipped in a solution. It remains red.

Question 9.
What is the nature of the solution? Explain your answer.
Answer:

  1. The solution may be neutral or acidic.
  2. Red litmus remains unchanged when dipped in acidic solution or neutral solution.

Question 10.
What is the effect of basic substances on turmeric paper?
Answer:
The turmeric paper turns red when basic substances come in touch with the turmeric paper.

AP Board 7th Class Science Solutions Chapter 2 Acids and Bases

Question 11.
Can flowers and turmeric papers also be called indicators? Why?
Answer:

  1. Flowers and turmeric papers are natural indicators.
  2. These change their colour based on the nature of the material put on them.

Question 12.
Correct the statement if it is wrong:
a) Indicators show different colours in acidic and basic solutions.
b) Sodium hydroxide turns blue litmus red.
c) Tooth decay is caused by the presence of base.
Answer:
a) Indicators show different colours in acidic and basic solutions.
b) Sodium hydroxide turns red litmus blue.
c) Tooth decay is caused by the presence of acid.

Question 13.
Take vinegar, lemon juice, soapy water, baking soda in different vessels. Put beetroot pieces in the vessels. Predict what happens? Verify your prediction by observing the changes. After 10 minutes, 30 minutes, 60 minutes record your observations. What do you conclude?
Answer:
The following are our predictions. These are found to be true when verified.

S.No. Acid Base
1. Vinegar Soapy water
2. Lemon juice Baking soda

Question 14.
Visit a doctor. Find out the medicines she prescribes to treat acidity. Ask her how acidity can be naturally prevented. Prepare a report.
Answer:

  1. Acidity arises due to hydrochloric acid present in the stomach.
  2. Acidity results in indigestion and a burning sensation in the stomach. Even it may cause headache.
  3. To treat acidity doctors give antacids. These will give relief from acidity and indigestion.
  4. Antacids contain sodium hydrogen carbonate. When these antacids are taken orally, they react with the hydrochloric acid present in the stomach and reduces its strength.
  5. Milk of magnesia is one such antacid.
  6. Eating at irregular intervals, skipping meals and eating too quickly are more reasons. Certain foods like tomatoes, lime juice, and oranges could also lead to acidity.
  7. Lack of exercise and stress also results in acidity or heart burn. Hence, the best way to avoid acidity is to avoid the factors that cause it.
  8. It is a must to avoid fried and oily foods, and one must drink plenty of water, at least 8-10 glasses everyday.
  9. Yogurt helps in easy digestion of food.

AP Board 7th Class Science Solutions Chapter 2 Acids and Bases

Question 15.
Prepare red cabbage juice by boiling a piece of red cabbage in water. Use it as an indicator and test acidic and basic solutions with it. Present your observations in the form of a table.
Answer:

  1. Red cabbage is cut into quarters. It is placed in a pot with a cupful of water and boiled.
  2. After about fifteen to twenty minutes, turn off the stove.
  3. Cut some plain white paper toweling into small strips. When the pots contents have cooled, transfer the cabbage water to a glass and dip several strips into it.
  4. Place them on a wax paper to dry.
  5. Let the cabbage water sit in the glass for several days in a warm, sunny spot in the home until a lot of water has evaporated.
  6. This will mean the cabbage water that remains is more concentrated.
  7. Dip strips of paper towel into this concentrated solution and lay them on a wax paper to dry.
  8. Use this home made litmus paper to test lemon juice (an acid) and baking soda mixed with water (a base).
  9. The observations are recorded.
    S.no Acid Base
    1. Vinegar Baking soda
    2. Lemon Soap
    3. Apple Milk of Magnesia
    4. Tomato Ammonia
    5. Banana Egg
    6. Milk Caustic soda
    water is neutral

Question 16.
Collect different flowers and prepare their natural indicators with the help of filter papers.
Answer:
Cut flower petals into strips or chop them in a blender. Place the cut pieces into a beaker or cup. Add just enough water to cover the plant material. Boil until the colour is removed from the plant. Filter the liquid into another container, such as a petri dish. Discard the plant matter. Saturate clean filter paper with the flower solution. Allow the filter paper to dry. You can cut the coloured paper with scissors to make pH test strips. Ex: Hibiscus, poinsettia, roses, etc.

Question 17.
Test the nature of lemon juice and milk sample with the help of natural indicators prepared from different flowers. Explain their nature.
Answer:
a) The petals of Hibiscus are taken as a natural indicator.
b) Their colour changed to red colour when tested with lemon juice.
c) This indicated that lemon juice is an acid.
d) The colour of the petals of Hibiscus remains unchanged when tested with milk.
e) This indicates that milk is neutral.

AP Board 7th Class Science Solutions Chapter 2 Acids and Bases

Question 18.
How do you feel about nature? Is it a big natural laboratory that contains innumerable indicators?
Answer:

  1. Nature is beyond the analysis of man.
  2. Nature is a big laboratory where several wonderful things happen. Only few will come to our observation.
  3. Not only flowers, even leaves of plants also behave like indicators showing the changes and indicating the presence of different substances.
  4. The fall of acid rain will be indicated by both flowers and leaves of certain plants.
  5. What is different from the existing immediately these indicators show their entry.

Question 19.
Choose the correct answer.
a) To protect tooth decay we are advised to brush our teeth regularly. The nature of the tooth paste commonly used is
i) Acidic
ii) Neutral
iii) Basic
iv) Baking soda
Answer:
iii) Basic

b) Which of the following is acidic in nature?
i) Lemon juice
ii) Baking soda
iii) Lime water
iv) Antacid
Answer:
i) Lemon juice

Question 20.
Match the following.
AP Board 7th Class Science Solutions Chapter 2 Acids and Bases 1
Answer:
AP Board 7th Class Science Solutions Chapter 2 Acids and Bases 2

AP Board 7th Class Science Solutions Chapter 2 Acids and Bases

Question 21.
Why industrial wastes are neutralised before releasing into water?
Answer:
The industrial wastes are neutralised before disposting into water bodies because, factory wastes often contain acid, if it reaches a river, the acid will kill aquatic life and thus brings damage to the entire ecosystem.