Physical Science What is a significant figure There are 2 kinds of numbers Exact the amount of money in your account Known with certainty What is a significant figure Approximate weight heightanything MEASURED No measurement is perfect ID: 402293
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Slide1
Significant Figures
Physical ScienceSlide2
What is a significant figure?
There are 2 kinds of numbers:
Exact: the amount of money in your account. Known with certainty.Slide3
What is a significant figure?
Approximate: weight, height—anything MEASURED. No measurement is perfect.
Slide4
When to use Significant figures
When a measurement is recorded only those digits that are dependable are written down. Slide5
When to use Significant figures
If you measured the width of a paper with your ruler you might record 21.7cm.
To a mathematician 21.70, or 21.700 is the same.Slide6
But, to a scientist 21.7cm and 21.70cm is NOT the same
21.700cm to a scientist means the measurement is accurate to within one thousandth of a cm.Slide7
But, to a scientist 21.7cm and 21.70cm is NOT the same
If you used an ordinary ruler, the smallest marking is the mm, so your measurement has to be recorded as 21.7cm.Slide8
How do I know how many Sig Figs?
Rule: All digits are significant starting with the
first non-zero
digit on the left.Slide9
How do I know how many Sig Figs?
Exception to rule:
In whole numbers that end in zero, the zeros at the end are not significant.Slide10
How many sig figs?
7
40
0.5
0.00003
7 x 10
5
7,000,000
1
1
1
1
1
1Slide11
How do I know how many Sig Figs?
2
nd
Exception to rule:
If zeros are sandwiched between non-zero digits, the zeros become significant.Slide12
How do I know how many Sig Figs?
3rd Exception to rule:
If zeros are at the end of a number that has a decimal, the zeros are significant. Slide13
How do I know how many Sig Figs?
3rd Exception to rule:
These zeros are showing how accurate the measurement or calculation are.Slide14
How many sig figs here?
1.2
2100
56.76
4.00
0.0792
7,083,000,000
2
2
4
3
3
4Slide15
How many sig figs here?
3401
2100
2100.0
5.00
0.00412
8,000,050,000
4
2
5
3
3
6Slide16
What about calculations with sig figs?
Rule: When
adding or subtracting
measured numbers, the answer can have no more places after the decimal than the LEAST of the measured numbers.Slide17
Add/Subtract examples
2.45cm + 1.2cm = 3.65cm,
Round off to = 3.7cm
7.432cm + 2cm = 9.432 round to
9cmSlide18
Multiplication and Division
Rule: When
multiplying or dividing
, the result can have no more significant figures than the least reliable measurement.Slide19
A couple of examples
56.78 cm x 2.45cm = 139.111
cm
2
Round to
139cm
2
75.8cm x 9.6cm = ?Slide20
The End
Have Fun Measuring and Happy Calculating!