Ans. Characteristics of solids
a. Solids have a definite shape, distinct boundaries and fixed volumes, that is, have negligible compressibility.
b. Solids have a tendency to maintain their shape when subjected to outside force.
c. Solids may break under force but it is difficult to change their shape, so they are rigid.
Ans.
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Ans.
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Ans.
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Ans.
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Q97. Complete the table.
Quantity |
Unit |
Symbol |
Temperature |
kelvin |
K |
Length |
metre |
m |
Mass |
kilogram |
kg |
Weight |
newton |
N |
Volume |
cubic metre |
m3 |
Density |
kilogram per cubic metre |
kg m–3 |
Pressure |
pascal |
Pa |
Ans. (a) Naphthalene balls disappear with time without leaving any solid because naphthalene balls undergo sublimation i.e. change of state directly from solid to gas without changing into liquid state (or vice versa). Naphthalene balls keep on forming naphthalene vapours slowly which disappear into the air.
(b) We can get the smell of perfume sitting several metres away due to diffusion of perfume vapours into air. The liquid perfume quickly changes into vapours. The perfume vapours move very rapidly in all directions in air, mix with the air particles and hence spread with air easily.
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Ans. A – Melting or Fusion
B - Vaporisation
C - Condensation
D - Solidification
E - Sublimation
F - Sublimation
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