Significant Figures - Chemistry

2 types of data

qualitative and quantitative

qualitative

o   Includes all non-numerical information obtained from observations not from measurement

o    Non number data

Eg: color change, bubblin

quantitative

o   Numerical information obtained from measurements

o   Affected by the type of instrument used and if it was correctly used or not, human limitations.

 Numbered data 

 

Measurement is defined as the

process of comparison of an unknown quantity with a known or standard quantity. 

Maths can be

used in chemistry to deal with numbers in a simple way.

 

 Eg: scientific notation 

 

Tools for measurement have

 

specific units

Any types of measurement can have

a margin of uncertainty

what are significant figures

 digits that count in values. They are a way to communicate how some measurements are 

 

what are exact numbers - what numbers have an infinite amount of significant figures?

1 Counting numbers have an infinite number of significant figures.

2.    Conversion factors have an infinite number of significant figures.

 

Recognizing Significant Figures have

four rules

rule 1 all nonzero

numbers are always significant.

Eg: 4.300500

rule 2 Placeholder zeroes are

not significant. To remove placeholder zeros, rewrite the number in scientific notation. 

Eg: 0.00056010 = 5.6010 x 10^-4

Rule 3: Any zero between  

significant figures is significant (middle zeros) e.g. 4.300500.

Rule 4: All final zeros to the right of the decimal are s

significant. 

Eg: 4.300500

Trailing zeros with a decimal are s

significant 

Eg: 410.   

 Eg: 120.0

 Trailing zero without decimal are

not significant 

Eg: 700 

Significant figure are different from

0, however in some cases it may count

00.007 =

leading 0s

7000

= trailing 0s

107 =

 

captive 0 s

2.000 =

multiple 0s after decimal point  - shows the extent the measuring tool can go to

Significant figures are not:

-             Leading 0s

-             Trailing 0s

Significant figures are:

 

 

-             Captive 0s 

-             Multiple 0s after the decimal point

   We also do not count the 0s that

can be changed into the power of 10 through scientific notation.

The amount of significant figures determines

the accuracy 

Why do we used significant figures?

 We use significant figures because they tell us how certain we are about a value. 

Every instrument has

limitations and uncertainty 

 

If the zero is written with the integer

keep it and count it as a sig fig

what is precision

clearness of repeated measurements under the same conditions to each other. The closeness of a set of measurements of the same quantity made in the same way.

   Degree of agreement of

among several measurements of the same quantity

Accuracy

How close a measured or calculated value is to the true measurement The closeness of measurements to the correct or accepted value of the quantity measured.

accuarcy - the agreement

The agreement of the particular value with the true value.