Question

Section-A
1. What is allotropy?
OR
Why are carbon and its compounds used as fuels for most applications?
2. Why does 1 M HCl solution have a high concentration of H' ions than 1 M CHCOOH
solution?
3. Which among the following is (are) double displacement reaction and why?
(i) Pb + CuCl2
→ PbCl₂ + Cu (ii) Na,SO4 + BaCl2 - BaSO4 + 2Nad
(iii) C + O2 --> CO2
(iv) CH4 + 202 CO2 + 2H20
(a) (i) and (iv) (b) (ii) only
(c) (i) and (ii)
(d) (iii) and (iv)
4. A ray of light passing through the centre of curvature of a concave mirror reflects back
along the same path. Why?
5. What happens to the ray of light on entering from denser medium to rarer medium?
6. Image distance for a spherical lens is negative. What does the negative sign signify? (1)
OR
A lens has two focal points, where as a mirror has only one. Why?
7. What is the value of magnetic field inside a current carrying solenoid?
8. Draw magnetic field lines around a bar magnet
9. A wire of resistance 10 ohm is bent in the form of a closed circle. What is the effective
resistance between the two points at the ends of any diameter of the circle?
OR
There are two electric bulbs, (i) marked 60 W, 220 V and (ii) marked 100 W. 220 V.
Which one of them has higher resistance?
10. Why do aquatic animals breathe faster than the terrestrial animals?
11. Give the respective scientific terms used for studying:
10
(a) The mechanism by which variations are created and inherited and
(b) The development of new type of organisms from the existing ones.
OR
Give an advantage of vegetative propagation.
12. All the variations in a species do not have equal chances of survival Why?
13. Name any three waste products of plants?
OR
Give the energy transformation that takes place in the​

Answer 1

1. Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner.

2. HCl is stronger than CH3COOH. There is complete dissociaton of HCl which produces more H+ ions as compare to CH3COOH which is weak acid. ... So, 1 M HCL have higher concentration than 1 M CH3COOH.

3. Double displacement reactions are those in which ions of the reactants are exchanged to form new compounds as products. 

In option (ii), 

Na+ion combines with Cl− ion and SO42− ion combines with Ba2+ ion to form two new compounds as sodium chloride (NaCl) and barium sulphate (BaSO4) respectively.

4. A ray of light passing through the centre of curvature of a concave mirror isreflected back along the same pathbecause it strikes the concave mirror at right angles to its surface due to which the angle of incidence and angle of reflection both are oo.

5. When light travels from a denser mediumto a rarer medium, it bends away from the normal, as illustrated to the left. This behavior follows from Snell's Law. As you saw before, the larger angle must be in the medium having the lower index of refraction.

6. When the image distance is positive, theimage is on the same side of the mirror as the object, and it is real and inverted. When the image distance is negative, theimage is behind the mirror, so the imageis virtual and upright. A negative mmeans that the image is inverted. Positive means an upright image.

7. Is the magnetic field inside a current carrying solenoid constant at all points? The magnetic field produced by a current carrying solenoid is same at all pointsinside it.

8. The properties of magnetic lines of forces are: 1) The direction of magnetic field lines outside the magnet sis from North Pole to South Pole. 2) The direction of magnetic field lines inside the magnetis from south pole to the north pole. 3) No two magnetic field lines intersect each other.

9. Therefore, the effective resistance between the two points at the end of any diameter of the circle is 2.5ohm.

10. The rate of breathing in aquaticorganisms is much faster than interrestrial organisms because the amount of dissolved oxygen is fairly lower in water than air and also thataquatic organisms like the fishes obtain oxygen from water present in the dissolved state.

11. (i) The respective scientific terms used for studying the mechanism by which variations are created and inherited is Reproduction.

12.  All variations in a species do not have equal chances of survival. Some of the variations may be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits.

13. The waste products of a plant are carbon dioxide, water vapour and oxygen. While carbon dioxide and water vapour arewaste products of respiration, oxygen is a waste product of photosynthesis. These waste products are removed through stomata in leaves and lenticels in stems and are released into the air.