Page 84 - SP015 Past Years PSPM Chapter 6 -14 Ver 2020

PHYSICS PSPM SEM 1 1999 - 2017

16. Coefficient of area thermal expansion,  is the fractional change in area per unit change in temperature.
17. Coefficient of volume thermal expansion is the change in volume per unit of its original volume per
unit change in temperature.
18. h = 11.011 m
-1
-5
19.  Hg = 15  10 C
-1
-6
-5
-1
20. (a)  A = 8  10 C ,  B = 3.5  10 C (b) L oA = 77.78 cm, L oB = 22.22 cm
-4
21.  L = 6  10 m
 L
-3
22. = 4.61  10
L
-1
-5
-5
23. (a) 2.6  10 K means for temperature increase of 1 K, fractional increase in length is 2.6  10 .
-5
(b) V = 3.74  10 m 3
24. T = 308 C
25. The frame must be heated to 35.15 C.
26. L = 3.0036 m
27. (a) T = 100.3 C (b) No.  aluminium >  brass
3
28. V = 2.5 cm

FINAL ANSWER FOR CHAPTER 13: GAS LAWS AND KINETIC THEORY

1. Ideal gas is gas that obeys all the law of gas such as Boyle’s law, Charles’ law, and law of pressure.
2. Ideal gas equation: pV = nRT
3. n = number of moles of the gas, N = number of molecules in the gas,
k = Boltzmann constant
3
4. V i = 0.026 m , p f = 11.45 atm
22
5. N = 9.03  10 molecules
6. (a) T f = 586 K (b) V f = 4 litres
3
3
7. V 1 = 89.6 dm , V 2 = 31.9 dm
17
8. N = 9.09  10 molecules
9. m new = 8.19 kg

10. Four assumptions of kinetic theory of gases.
 Gas consists of identical spherical molecules.
 Molecules move in random motion.
 Intermolecular forces are negligible.
 Volumes of molecules are negligible.
 Collisions between molecules are negligible.
 Collision time can be neglected compared to time between collision

11. Assumptions about molecules to obtain the relation between pressure and density of ideal gas,
2
1
p =  < v > is assumptions of kinetic theory of gases.
3
 Gas molecules collide elastically with each other and with the walls of the container  kinetic
energy and momentum are conserved. Collision of gas molecules with the walls of the container
produces pressure on the walls.
 Gas molecules are at constant, free, and random motion to all directions with different velocity
 Forces between molecules are negligible except during collision.

2
12. (a) < v > represents mean square velocity of gas molecules.
(b) rms velocity =  v 2  (c) The expression in (b) remains the same.
13. v rms increases by 22%.
14. T 2 = 294 K
-1
15. v rms = 0.79 m s
-1
16. v = 229 m s
3
17. K tr = kT
2
18. (a) Degree of freedom of gas molecules is the number of ways in which an atom or molecule can
absorb or store energy.

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