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Q1 What are canal rays?
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Q2 If an atom contains one electron and one proton, will it carry any charge or not?
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Until the structure of atom reveals it was thought atom are indivisible but as the modern technology is advancing more and more. We came to know that these atoms are made of subparticle and they together form an atom. An atom contain positive and negative charges, but yet is electrically stable.
Download pdf of NCERT Solutions for Class Science Chapter 4 Structure of the Atom
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Q1 | What are canal rays? |
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Q2 | If an atom contains one electron and one proton, will it carry any charge or not? |
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Q1 | On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole. |
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Q2 | On the basis of Rutherford’s model of an atom, which sub-atomic particle is present in the nucleus of an atom? |
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Q3 | Draw a sketch of Bohr’s model of an atom with three shells. |
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Q4 | What do you think would be the observation if the α-particle scattering experiment is carried out using a foil of a metal other than gold? |
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Q1 | Name the three sub-atomic particles of an atom. |
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Q2 | Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have? |
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Q1 | Write the distribution of electrons in carbon and sodium atoms. |
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Q2 | If K and L shells of an atom are full, then what would be the total number of electrons in the atom? |
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Q1 | How will you find the valency of chlorine, sulphur and magnesium? |
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Q1 | If number of electrons in an atom is 8 and number of protons is also 8, then (i) what is the atomic number of the atom? and (ii) what is the charge on the atom? |
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Q2 | With the help of Table 4.1, find out the mass number of oxygen and sulphur atom. |
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Q1 | For the symbol H,D and T tabulate three sub-atomic particles found in each of them. |
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Q2 | Write the electronic configuration of any one pair of isotopes and isobars. |
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Convert into mole.
(a) 12 g of oxygen gas
(b) 20 g of water
(c) 22 g of carbon dioxide.
Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?
Why is the atmosphere essential for life?
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled?
Why are we normally advised to take bland and nourishing food when we are sick?
Why is the weight of an object on the moon 1/6th its weight on the earth?
What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?
In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
• if you get jaundice,
• if you get lice,
• if you get acne.
Why?
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity.
Under which of the following conditions are you most likely to fall sick?
(a) when you are taking examinations.
(b) when you have travelled by bus and train for two days.
(c) when your friend is suffering from measles.
Why?
List any three human activities that you think would lead to air pollution.
Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium suphide
(iv) magnesium hydroxide
Find the energy in kW h consumed in 10 hours by four devices of power 500 W each.
Why is it not possible to see an atom with naked eyes?
What are polyatomic ions? Give examples.
Give three features of cardiac muscles.
How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm? Take its downward acceleration to be 10 m s-2.
Akhtar, Kiran and Rahul were riding in a motorcar that was moving with a high velocity on an expressway when an insect hit the windshield and got stuck on the windscreen. Akhtar and Kiran started pondering over the situation. Kiran suggested that the insect suffered a greater change in momentum as compared to the change in momentum of the motorcar (because the change in the velocity of the insect was much more than that of the motorcar). Akhtar said that since the motorcar was moving with a larger velocity, it exerted a larger force on the insect. And as a result the insect died. Rahul while putting an entirely new explanation said that both the motorcar and the insect experienced the same force and a change in their momentum. Comment on these suggestions
A hammer of mass 500 g, moving at 50 m s-1, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer?