PQM ( physical quantities and measurements)
Physical properties of matter
Flexibility
Hardness
Melting point
Boiling point
Strength
Electrical conductivity
Thermal conductivity
Density
The ability of a material to:
• bend without breaking; return to its original size and shape after bending.
The ability of a material to withstand scratches.
The temperature at which a material changes
in state from a solid to a liquid.
The temperature at which a material changes
in state from a liquid to a gas.
A measure of how readily electricity passes
though the material.
The quantity of matter packed into a unit
volume of the material.
The ability of a material to support a heavy
load without breaking or tearing.
A measure of how readily heat passes
through the material.
Units for measurements
Physical quantities are quantities that can be measured.Some examples include length, area, volume, mass and
time
Systeme International d’Unites or S.I. units are the most
commonly used system of units in science.
S.I. unit of length is metre. The symbol for the metre is
m.
When incorrect positioning of the eye occurs when making
a measurement, parallax error occurs.
Parallax errors can be avoided by placing your eyes directly
and perpendicularly above the point of measurement
Using the Vernier calipers
- Close the jaws of the Vernier calipers completely.
- Read off the zero-error (if any).
- Open up the jaws and place the object within the jaws of
the Vernier calipers and clamp it firmly in place.
- Read the main scale reading.
- Read the vernier scale reading.
- Add the vernier scale reading to the main scale reading
to obtain the observed reading.
- Compensate for zero-error (if any) to get the actual
reading.
If the ‘0’ on the vernier scale is on the right side of the main scale’s ‘0’,
the zero error is a positive value.
If the ‘0’ on the vernier scale is on the left side of the main scale’s ‘0’,
the zero-error is a negative value.
Estimation of areas can be done with the help of a square grid
whose sides are of known lengths.
A square of area 1 cm2 that is filled up by more than half of
its area is counted as 1 full square.
Reading the meniscus
❑ In narrow glass cylinders, the liquid level is curved into a shape called the meniscus.
❑ Position your eye at the same level as the bottom of the meniscus to avoid parallax error.
Always record your answer with 2 d.p.
Measuring volumes of irregularly-shaped solids
The volume of a small, irregularly-shaped object can be
measured by the displacement method. This is done with the aid
of a measuring cylinder or a displacement can.
When using the displacement method, the object has to be fully
submerged in the water in order to determine a valid volume.
Mass versus weight
mass
weight
definition:Mass is the amount of
matter in the substances.
definition:Weight is a
measurement of the
gravitational force acting
on an object.
Mass is expressed in
kilogram (kg),grams (g),
and milligram (mg)
Weight is expressed in
newton (N)
Mass is measured using
a pan balance, a beam
balance, lever balance or
electronic balance
Weight is measured
using a spring balance
Density
Density = Mass over
Volume
Average speed
average speed= total distance travelled over total time taken