Important questions for class ix

CHEMISTRY

1. State the postulate of Dalton’s Atomic theory that explains Law of Conservation of

Mass.

2. (a) Define the atomic mass unit.

(b) Write the chemical formulae of :

(i) Ammonium Carbonate (ii) Sodium Oxide

(c) Write the name of the compound Al2(SO4)3 and mention the ions present in it.

3. State the features of Rutherford’s atomic model.

4. If an element ‘X’ is available in the form of say, two isotopes ⁷⁹₃₅Br(49.7%) and ⁸¹₃₅Br(50.3%), calculate the average atomic mass of the atom of ‘X’.

5. (a) Define (i) Molar mass (ii) Avogadro constant

(b) What is the mass of 0.5 mole of NH3 ? Given Atomic mass of N = 14u, Atomic

mass of H = 1u.

(c) Calculate the number of particles in 31 g of P4 molecules. Atomic mass of

P=31u. (No 6.0221023 per mole)

(d) Find the number of moles in 87g of K2SO4 (Atomic mass of K=39u, S=32u,

O=16u)

6. (a) Define (i) Formula unit mass (ii) Polyatomic ion.

(b) Calculate the number of moles for the following.

(i) 36g of He (At. Mass of He 4 u) (ii) 12.04410²³ molecules of H₂O (At.mass of He1 u, O16 u)

(c) How many atoms are present in -

(i) SO₄^2- ion ? (ii) NH₄⁺ion ?

PHYSICS

1. State Archimedes’ principle. Based on this principle, write any one application.

2. List two conditions which need to be satisfied for the work to be done on an object ?

3. (a) School bags are provided with broad straps. Give reason.

(b) The relative density of iron is 7.8. What will be the mass of an iron brick with

dimensions 5 cm  10 cm  20 cm ? (Density of water is 1 g/cc)

4. Define 1 watt of power. A lamp consumes 1000 J of electrical energy in 10s. Calculate

its power.

5. How much work should be done on an object of 120 kg to increase its speed from 25

m/s to 40 m/s ?

6. A radio station is transmitting its signals at a frequency 400 Mhz. If the velocity of radio waves is 3*10⁸ m/s, Calculate the wavelength of radio waves.

7. (i) A light and a heavy object have the same momentum. What is the ratio of their kinetic energies ? Which one has a larger kinetic energy ?

(ii) A ball is dropped from a height of 10m. If the energy of the ball reduces by

40% after striking the ground, how much high can the ball bounce back ?

(g = 10ms^-2)

8. (i) State the law of conservation of energy.

(ii) Show that the energy of a freely falling body is conserved.

9. ‘Sound wave is a longitudinal wave and requires a material medium to propagate’.

Justify this statement with the help of an experiment.

10. What is an echo? What should be the minimum distance of the obstacle from the source of sound to hear an echo. An echo returned in 2 seconds. What is the distance

of the reflecting surface from the source, given that the speed of sound is 340 m/s.

BIOLOGY

1. Write the name of the group of plants which produces seeds but not fruits.

2. List any two human activities that you think would lead to air pollution.

3. State two reasons why whales are not grouped with fishes ?

4. List four ways of spreading communicable diseases.

5. On what basis are plants and animals put into different categories? Write points.

6. Write one point of difference each, between the following :

(a) Amphibians and Reptiles

(b) Aves and Mammals

(c) Gymnosperm and angiosperm

7. Write one point of difference each, between the following :

(a) Amphibians and Reptiles

(b) Aves and Mammals

(c) Gymnosperm and angiosperm

8. State two causes and two effects of depletion of ozone layer in the atmosphere.

9. (a) What is meant by acid rain? How has it affected the environment and historical monuments ?

(b) What is smog ? Name two diseases caused by smog.

10. (a) State two characteristic features of Bryophytes.

(b) Identify the class to which the following belong :-

(i) Cold blooded animals with scaly skin and two chambered heart.

(ii) Egg laying warm blooded animals with four chambered heart.

(iii) Cold blooded animals with scales and laying eggs near water.

11. (a) What are diploblastic and triploblastic animals ?

(b) How are breathing organs of fish and lizard different ?

(c) What is notochord ?

12. (a) Name two processes that remove O2 from the atmosphere and a process that

adds O2 to the atmosphere.

(b) Draw a schematic diagram to show how O2 is cycled in the atmosphere.

13. What is a Biogeochemical cycle ? List and explain the four steps of N cycle in nature.