## Saturday, February 2, 2013

### CBSE Class 9 - Science - Value Based Questions -1

Science - Value Based Questions
(Part-1)
[Gravitation, Pressure and Archimedes Principle]
 Bed Of Nails - A circus trick image credits: Jendi's Journal
Q1:  Bhola was impressed by the miracle performed by Baba Bandar Nath when Baba lied down on a bed of nails. The nails did not hurt him. Bhola narrated about this miracle to his friend Rithik. Rithik explained to Bhola that there is no magic or miracle here. Even he can also do the same trick.

(a) Why did Rithik say that there is no 'miracle' in this trick? Why did Baba Bandar Nath did not hurt himself?
(b) Which quality is shown by Rithik here?

(a) Rithik is right that there is no miracle here. We know that pressure is defined as force acting per unit area. If you step up on a nail, the entire body weight exerts more pressure because the area of nail tip is very small. In case of bed of nails, the pressure exerted by the weight of the body is distributed among the hundreds or thousands of nails lying close to each other. Thus the net pressure on a nail is very small.

(b) Rithik applied the logic to understand how things works. He also helps his friend by creating awareness about such myths or misconceptions.

Q2(EduDel): While passing nearby a pond, some students saw a drowning man screaming for help. They alerted another passerby, who immediately threw an inflated rubber tube in the pond. The man was saved.
(a) Why the passerby did use inflated rubber tube to save the drowning man?
(b) Write the principle involved here.
(c) Which qualities shown by the students and the passerby do you identify that helped in saving the drowning man?

Answer: (a) The average density of inflated rubber tube is less than the density of water, therefore it floats on the water. The buoyant force exerted by the water is higher than the weight of the tube immersed in the water.

(b) It follows Archimedes Principle of Buoyancy.

(c) Students and the passerby have helping & caring nature. Passerby also applied the scientific principles practically.

Q3: The milkman in our society started carrying lactometer. His move was well appreciated by the society members.
(a) What is the use of lactometer? On What principle it works?
(b) What values of milkman is shown by the milkman?

Answer: (a) Lactometer is used to test the purity of milk. It works on Archimedes Principle of Buoyancy.
(b) It shows mikman's honesty.

Q4(EduDel): During the summer vacations, Gaurav visited his native village. He observed that for washing clothes, villagers used the water from the well. Out of curiosity he drew water from the well and observed that the bucket of water appeared to be heavier as it came out of the water.
(a) Name the principle used in the above passage.
(b) Why bucket appears to be heavier in air?
(c) Which values are reflected in Gaurav's behavior.

Answer: (a) While drawing water with the help of bucket, Gaurav works against force due to gravity. Here Newtons Law of gravitation is applied. The bucket appears heavier in air than in water, Archimedes principle is applied.

(b) Bucket in air appears heavier than that of in water, because the buoyant force exerted by water on the immersed bucket leads to an apparent loss of weight of the bucket. That's why Gaurav felt the bucket heavy in air as compared to it in water. While drawing bucket, he is working against gravity.

(c) It shows his curiosity and eagerness to learn and apply scientific principles.

[ATOMS and MOLECULES]

Q5: Bhola again was impressed by Baba Bandarnath's miracle when Baba bent the water stream without touching. He did so by bringing a big balloon near to the flowing water. Bhola narrated his experience to Rithik telling about Baba's magical hand.
Rithik explained Bhola that it was a very simple trick. He told Bhola this is nothing but the molecules of water and Balloon interact with each other due to charges on them.

(a) What property of atoms and molecules Rithik is trying to explain here?
(b) What values are exhibited by Rithik here?

Answer: (a) Positive charge on Water molecules (polar molecule) are attracted towards the negative charged balloon. All matter consists of molecules and atoms. Atoms contain sub-atomic particles called electrons. Electrons are negatively charged and largely responsible for the interaction between two substances.

(b) It shows Rithik tries to apply scientific logic explaining how things work or interact. He also wants to create awareness among others against myths and misconceptions.

Q6(EduDel): An old man and a scientist were talking about a deserted house. The old man was sure that it was haunted by ghosts, but the scientist discarded the view saying no one had ever seen a ghost. The old man was annoyed and challenged the scientist about existence of atoms, sub-atomic particles which also could not be seen.

(a) Name the three sub-atomic particles and their discoverers.
(b) Whose viewpoint do you support and why?

Answer: (a) The three sub-atomic particles and their discoverers are:
1. Electrons - J J Thomson
2. Protons - Goldstein
(b) I support scientist's viewpoint because it is based on logic and proven facts. Old man's views are figments of imagination without any scientific truth and are superstitions.

Q7(EduDel): An activity was conducted in a classroom where students held placards with symbols and valency of the elements separately. Each student held two placards, one with the symbol in the right hand and other with the valency in the left hand.

(a) Which placards will be required for formation of sodium chloride ( both symbol as well as valency).
(b) Which qualities are required in the student to perform such a group activity?

Answer: (a) Sodium - Na(1+), Chlorine - Cl(1-)
(b) Team co-ordination and knowledge about chemical symbols.

Q8(EduDel): Two class IX students, Kaveri and Nalin, were asked to take 5.3 g of sodium carbonate and 6g of ethanoic acid to make 2.2g of carbon dioxide, 0.9g of water and 8.2 g of sodium ethanoate. Kaveri followed the instructions but Nalin took the chemicals without measuring their amounts.

(a) Whose activity do you think will be in agreement with the law of ``Conservation of mass''?
(b) State the law of ``Conservation of mass''.

(c) Whose method do you like and why?

Answer: (a) Kaveri's method is in agreement with the law of 'Conservation of mass'.

(b) According to Law of conservation of mass, in an isolated system, mass of the reactants is equal to mass of products. It implies mass can neither be created or destroyed in any ordinary chemical reaction.

(c) I like Kaveri's method since she followed the experiments taking precise and accurate measurements.

Q9(EduDel): Raghu and Vansh were performing an activity related to conservation of mass in chemistry lab of their school. They mixed a solution of barium chloride and sodium sulphate. Raghu suggested that as they already knew the amount of both compounds taken by them, they need not to measure the amount of final solution. On the contrary, Vansh insisted to measure the amount of final solution, which had barium sulphate and sodium chloride. Atomic mass of ions: Ba2+ = 137 units, Cl- = 35.5 units, Na+ = 23 units, S2- = 32units, O2- = 16 units.

i.) Determine the molecular mass of
a) Barium chloride
b) Barium sulphate
c) Sodium sulphate
d) Sodium chloride

ii) Comment on Vansh's Insistence to complete the activity.

Answer: i). (a) Barium Chloride = BaCl2 = 137units + 2×(35.5units) = 137 + 71 = 208 units
(b) Barium Sulphate = BaSO4 = 137 + 32 + 4×(16) = 137 + 32 + 64 = 233units
(c) Sodium Sulphate = Na2SO4 = 23×2 + 32 + 4×(16) = 46 + 32 + 64 = 142 units
(d) Sodium Chloride = NaCl = 23 + 35.5 =  58.5 units

ii). Constant verification is part of a scientific method. Vansh's insistence reflects his scientific temper towards applying logic.

[WHY DO WE FALL ILL]

Q10(CBSE Sample Paper): The number of dengue cases had increased in Pooja’s village in last one year. She read in her textbook that diseases like dengue spread through mosquitoes which breed in stagnant water. She immediately suggested her friends and decided to kill the mosquitoes in water bodies in the locality. They also took help of nearest municipal office.
Answer the following questions based on above information:

i) Which preventive measures do you suggest for the prevention of such diseases caused by mosquitoes? Mention any two measures.
ii) Which values are displayed by Pooja in taking initiative?
iii) Suggest one school activity to promote such values in school students.

Answer: i) Water logging in neigbourhood, at roofs, air-coolers etc. should be avoided. Fumigation and disinfection sprays should be conducted regularly. Use mosquito nets and repellents at home.

ii). Pooja understands 'Prevention is better than cure'. She also understands her social and civic responsibility towards keeping a clean and hygienic environment.

iii) School should conduct awareness campaigns and debates on 'How to keep our environment clean and hygienic".

Q11: Ankit has flu with fever. He insists on playing outside with his friends. His mother suggests him that he should not go out rather stay at home. Ankit does the same.

(a) Why Ankit's mother asks him to stay at home?
(b) What is cause of flu?
(c)  What values are shown by Ankit's mother?

Answer: (a) Ankit's mother ask him to stay at home because he might spread the flu to other who comes in contact with Ankit. Common cold is a communicable disease.

(b) Flu or common cold is caused by viruses.

(c) Ankit's mother shows her social responsibility.

Q12(EduDel): Two HIV- infected siblings Anu and Nikhil were expelled from their school. Only after the intervention of a NGO, they were readmitted.

(a) Which disease are the two children suffering from?
(b) Write any three modes of transmission of this disease.
(c) What is your viewpoint about both the steps taken by the school as well as the NGO?

Answer:  (a) Two children suffer from AIDS.

• blood transfusion
• sharing of syringes or needles, razors etc.
• inheritable i.e. passes through infected mother to foetes.
• sexual contact.
(c) School viewpoint is wrong. AIDS does not spread through sharing food, playing, mosquito bite etc.

Q13(EduDel): Akshita came to school one day with running nose, reddish and watery eyes and coughed often. She met Sanchita in the morning assembly who advised her to sit on a separate desk in the classroom till she recovers

(a) Name the disease from which Akshita is suffering from?
(b) Name the causal organism.
(c) Enlist any two preventive measures.

Answer: (a) Akshita might be suffering from common cold or flu or Influenza.

(b) Cold is caused by virus.

(c) Isolation, personal hygiene, avoid contacting others and self-discipline (e.g. sharing pillows or towels should be avoided).

(d) Sanchita is aware about how diseases spread and what precautions should be taken.