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Plus one (+1 ) physics
Chapter 1
Some Basic Concepts of Chemistry
Chapter 1
Units and measurements.
Rule for determining significant figure.
(1) All non-zero digits are significant. For
example in 285 cm, there are three
significant figures and in 0.25 mL, there
are two significant figures.
(2) Zeros preceding to first non-zero digit are
not significant. Such zero indicates the
position of decimal point.
Thus, 0.03 has one significant figure and
0.0052 has two significant figures.
(3) Zeros between two non-zero digits are
significant. Thus, 2.005 has four significant
figures.
(4) Zeros at the end or right of a number are
significant provided they are on the right
side of the decimal point. For example,
0.200 g has three significant figures.
But, if otherwise, the terminal zeros are not
significant if there is no decimal point. For
example, 100 has only one significant
figure, but 100. has three significant
figures and 100.0 has four significant
figures. Such numbers are better
represented in scientific notation.
(5) Counting numbers of objects, for example,
2 balls or 20 eggs, have infinite significant
figures as these are exact numbers and can
be represented by writing infinite number
of zeros after placing a decimal i.e.,
2 = 2.000000 or 20 = 20.000000
Here, 18.0 has only one digit after the decimal
point and the result should be reported only
up to one digit after the decimal point which
is 31.1.
Multiplication and Division of Significant Figures
In these operations, the result must be reported
with no more significant figures as are there in
the measurement with the few significant
figures.
2.5×1.25 = 3.125
Since 2.5 has two significant figures, the
result should not have more than two
significant figures, thus, it is 3.1.
While limiting the result to the required
number of significant figures as done in the
above mathematical operation, one has to keep
in mind the following points for rounding off
the numbers
1. If the rightmost digit to be removed is more
than 5, the preceding number is increased
by one. for example, 1.386
If we have to remove 6, we have to round it
to 1.39
2. If the rightmost digit to be removed is less
than 5, the preceding number is not changed.
For example, 4.334 if 4 is to be removed,
then the result is rounded upto 4.33.
3. If the rightmost digit to be removed is 5,
then the preceding number is not changed
if it is an even number but it is increased
by one if it is an odd number. For example,
if 6.35 is to be rounded by removing 5, we
have to increase 3 to 4 giving 6.4 as the
result. However, if 6.25 is to be rounded
off it is rounded off to 6.2.
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