Significant Figures Physical Science

What is a significant figure? There are 2 kinds of numbers: –Exact: counting objects, or definitions. –Approximate: weight, height— anything MEASURED. No measurement is perfect.

When to use Significant figures When a measurement is recorded only those digits that are dependable are written down.

When to use Significant figures If you measured the bolt you might record 6.3cm. To a mathematician 6.3, or is the same. Is it okay to say the bolt is cm long?

But, to a scientist 6.3cm and cm is NOT the same cm to a scientist means the measurement is accurate to within one ten thousandth of a cm!

If you used an ordinary ruler, the smallest marking is the mm, so your measurement has to be recorded as 6.3cm. But, to a scientist 6.3cm and cm is NOT the same

Significant Figures …are those digits that carry meaning contributing to the precision of a measurement. The more sig fig’s, the more precise the measurement.

How do I know how many Sig Figs? Rule 1: All non zero digits are significant.

How do I know how many Sig Figs? Rule 2: If zeros are between non-zero digits, the zeros are significant

How do I know how many Sig Figs? Rule 3: Zeros after the decimal AND at the END of the number are also significant

How do I know how many Sig Figs? Rule 4: Zeros are NOT significant if… -they are at the end AND before the decimal

How do I know how many Sig Figs? Rule 4: Zeros are NOT significant if… -they are at the beginning

How many sig figs? ,000,

How many sig figs? ,000,

How many sig figs here? ,083,000,

How many sig figs here? x

What about calculations with sig figs? Rule: When adding or subtracting; determine which measurement’s sig figs end in the largest place, (tens, ones, tenths, etc.), then round of your answer to that place.

Add/Subtract examples 2.45cm + 1.2cm = 3.65cm, Round off to = 3.7cm 7480cm cm = 9680 Round to  9700cm

Multiplication and Division Rule: When multiplying or dividing, the answer can only have as many sig figs as the measurement that has the fewest amount of sig figs.

A couple of examples cm x 2.45cm = cm 2 Round to  139cm cm x 9.6cm = cm 2 730cm 2 Round to 

The End Have Fun Measuring and Happy Calculating!