PROPERTIES OF MATTER
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| PROPERTIES OF MATTER |
Physical properties of matter can be observed and tested. They include properties such
as color, length, volume, odor, and density. These properties are
extensive if they depend on the amount of the substance being used or intensive
if they do not depend on the amount of substance being used.
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| PROPERTIES OF MATTER |
ELASTICITY
Elasticity
is the property of material of a body by virtue of which the body acquires its
original shape and size after the removal of deforming force.Steel is more
elastic than rubber.
The
internal restoring force acting per unit area of cross section of a deformed
body is called stess.
The
fractional change in configuration i.e., length,volume and shape is called
strain.
PRESSURE
Pressure
is defined as force acting normally on unit area of the surface.
Pressure
= Force/Area
Atmospheric
pressure = 1.01 bar = 1.01✕105N/m2
Atmospheric
pressure is measured by barometer.
Atmospheric
pressure decreases with altitude (height from earth's surface). This is why
i. It is
difficult to cook on the mountain.
ii.The
fountain pen of a passenger leaks in aeroplane at height.
The
pressure exerted by liquid a depth h below the surface of liquid is given
as
p = hdg,
where d is density of liquid.
Pressure
at a point in a static liquid has same value in all direction.
Pressure
at a point in a liquid is proportional to the density of the liquid.
Pressure
at a point in a liquid is proportional to the depth of the point from the free
surface.
Boiling
point of all substances increases with the increase in pressure.
BUOYANT FORCE
When a
body is immersed partially or wholly in a liquid, a force acts on the body by
the liquid in the upward direction.
This
force is called buoyant force of buoyant of upthrust.
It is
equal to the weight of liquid displaced by the body and acts at the centre of
gravity of displaced liquid.
ARCHIMEDES PRINCIPLE
When a
solid body is immersed wholly or partially in a liquid (in general,in a fluid),
then there is some apparent loss in its weight.This loss in weight is equal to
the weight of the liquid displaced by the body.
LAW OF FLOTATION
When body
floats in neutral equilibrium,the weight of the body is equal to the weight of
displaced liquid.
The
centre of gravity of the body and centre of gravity of the displaced liquid
should be in one vertical line.
⇒The centre of gravity of a body
is that point at which the whole weight of the body appears to act.
DENSITY
Density
is defined as mass per unit volume.
Density = Mass /Volume
Its SI unit is Kg/m3.
Relative density = Density of material / Density of water
at 40C
Relative
density is measured by hydrometer.
The
density of sea water is more than of normal water.This explains why it is
easier to swim in sea water.
If ice
floating in water in a vessel melts, the level of water in the vessel does not
change.
The
density of water is maximum at temperature 40C.
SURFACE TENSION
Surface tension of a liquid is measured by the normal force
acting per unit length on either side of an imaginary line drawn on the free
surface of liquid and tangential to the free surface.
If a force F acts on an imaginary line of length l,then
surface tension T = F/l
Its SI unit is Newton/metre.
The surface tension of a liquid decrease with increase in
temperature.
⇒Force of attraction applied between molecules of same substance is
called cohesive force while attractive between molecules of different
substances is called adhesive force.
ANGLE OF CONTACT
The angle inside the liquid between the tangent to the solid
surface and the tangent to the liquid surface at the point of contact is called
the angle of contact for that pair of solid and liquid.
The angle of contact for pure water and clean glass is
zero.For ordinary water and glass it is about 80 C.
The liquid which do not wet the solid have obtuse angle of
contact as for mercury and glass the angle of contact is 1350 C.
The angle of contact for water and silver is 900 C.
CAPILLARITY
If a capillary tube is dipped in a liquid, liquid ascends of
descends in the capillary tube.This phenomenon is called capillarity.The oil in
the wick of a lamp rises due to capillary action of threads in the wick.The
root hairs of plants draws water from the soil through capillary action.
To prevent loss of water due to capillary action, the soil is
loosened and split into pieces by the farmers.
VISCOSITY
Viscosity is the property of a liquid by virtue of which it
opposes the relative motion between its different layers.
Viscosity is the property of liquids and gases both.
With rise in temperature, viscosity of liquids decreases and
that for gases increase.
BERNOULLI'S THEOREM
When an in compressible and non-viscous liquid (or gas)
flows in streamlined motion from one place to another,then at every point of
its path the total energy per unit volume (pressure energy + kinetic energy+
pressure energy) is constant.Venturimeter a device used to measure rate of flow of fluid,
works on Bernoulli's theorem.
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