Q. How kinetic molecular model of matter is helpful in
differentiating various state of matter?
Ans.
The distance between the molecules of solids, liquids and gases is different
according to the kinetic molecular theory. And by finding the density,
solubility and motion of molecules, the various states can be differentiated
with the help of kinetic molecular theory.
Q. Does there exist a fourth
state of matter? What is that?
Ans.
There exists forth state of matter which is called plasma. It consists of positive
ions and electrons at very high temperature.
Q. What is
meant by density? What is its SI unit?
Ans.
“Density of a substance is defined as its mass per unit volume.”
Its
SI unit is kilogram per cubic meter “kilogram per cubic meter”
Q. Can we use a hydrometer to measure the density of
milk?
Ans.
Hydrometer can be used to measure the density of milk, but special hydrometer
called lactometer is used for this purpose.
Q. Define the term pressure.
Ans.
“The force acting normally per unit area on the surface of a body is
called pressure.”
Thus,
Q. Show that atmosphere exerts pressure.
Ans.
When hot can is put into the cold water the can will collapse. The air pressure
inside the hot can and the air pressure outside of the hot can are the same,
when the can is cooled quickly the can collapses before it has a chance to equalize
pressures by allowing more air into the can. This shows that atmosphere exerts
pressure in all direction.
Q. It is easy to fill air in a balloon but it is very
difficult to remove air from a glass bottle. Why?
Ans.
To fill air in balloon is easy by applying pressure but in case of glass it is
difficult to remove air due to atmospheric pressure. The pressure inside the
glass is low than atmospheric pressure.
Q. What is a barometer?
Ans.
The instrument that is used to measure the atmospheric pressure is called
barometer.
Q. Why water is nor suitable to be used in barometer?
Ans.
The density of water is less than the density of mercury. If water is used in
barometer a long tube about 10 m is required which is inconvenient.
That’s why water cannot be used in barometer.
Q. What makes a sucker pressed in a smooth wall sticks
to it?
Ans.
When sucker is pressed on smooth wall the sucker pumps out the air due to which
pressure outside the sucker becomes greater than the inside pressure. It helps
to stick it with smooth wall.
Q. Why does the atmospheric pressure vary with height?
Ans.
With the increase in height the density of air decreases due to which
atmospheric pressure also began to low.
Q. What does it mean when the atmospheric pressure at a
place fall suddenly?
Ans.
When the atmospheric pressure at a place fall suddenly, the coldness produces
and it may be storm or rain at that place.
Q. What changes are expected in weather in if the
barometer reading shows a sudden increase?
Ans.
When the barometer reading increases suddenly due to increase in pressure of
the air, then the temperature of atmosphere rises.
Q. State Pascal’s law.
Ans.
It states that “Pressure applied at any point of a liquid enclosed in a
container, is transmitted without loss to all other parts of the liquid.”
Q. Explain the working of hydraulic press.
Ans.
This is long question…
Q. what is meant by elasticity?
Ans.
The property of a body to resist its original size and shape as the deforming
force ceases to act is called elasticity.
Q. State Archimedes principle.
Ans.
It states that “When an object is totally or partially immersed in a
liquid, an upthrust acts on it equal to the weight of
the liquid it displaces”.
Q. What is up thrust? Explain the principle of
flotation.
Ans.
When an object is immersed in liquids an upward force is exerted by the
liquids, that force is known as up thrust.
Principle
of flotation:
“A
floating object displaces a fluid having weight equal to the weight of the
object”
The
object will not sink and keep floating.
Q. Explain how a submarine moves up the water surface
and down into water.
Ans.
When water is removed from submarine weight of submarine becomes less than the
up thrust and it moves up the water surface. When it is filled with sea water,
its weight becomes larger than the up thrust and goes down into water.
Q. Why does a piece of stone sink in water but a ship
with a huge weight floats?
Ans.
When a piece of stone is placed in water it sinks because the up thrust acting
on it is less than its weight but shape of ship is made such that the up thrust
acting on it is greater than its weight so it floats on water.
Q. What is Hook’s law? What is meant by elastic
limit?
Ans.
“The strain produced in a body by the stress applied to it is directly
proportional to the stress within the elastic limit of the body.”
Thus,
Stress
Strain
Or Stress
= constant x strain
Or 
Elastic
limit:
“The
limit within which a body recovers its original length, volume or shape after
the deforming force is removed is called elastic limit”
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