SI Base Units

SI Base Units

Length Meter (m)

Time Second (s)

Mass Gram (g)

Current Ampere (A or amp)

Temperature Kelvin (K)

Luminous Intensity Candela (Cd)

Amount of Substance Mole (mol)

Prefixes to Memorize.

femto f 10-15

pico p 10-12

nano n 10-9

micro µ 10-6

milli m 10-3

centi c 10-2

deci d 10-1

BASE UNITS BASE UNITS BASE UNITS

deka da (or dk) 101

hecto h 102

kilo k 103

mega M 106

giga G 109

tera T 1012

Significant DigitsSignificant Figures

You will be asked to round to 3 significant figures

But first you must know how to determine whether a number is considered significant

Rule 1

1. All digits 1-9 are significant

789 3 sig figs

12587 5 sig figs

1.234 4 sig figs

Rule 2 ~ BETWEEN

Any zero between two significant digits is automatically significant

1003 4 sig figs

10.03 4 sig figs

1,000,007 7 sig figs

Rule 3 ~ FINAL ZERO

Any FINAL ZERO (after the decimal point) is significant.

12.30 4 sig figs

3.5768000 8 sig figs

4.0 2 sig figs

Rule 4 ~ placeholder

400

1 sig fig

10000 1 sig fig

789,600

4 sig figs

0.00059 2 sig figs

0.000590 3 sig figs

Any zero is insignificant if it is not between two sig digits nor the final zero after a decimal point. Theses zeros are called placeholders.

Examples

30040 grams

4 sig figs

The last zero is not significant

0.663 kg

3 sig figs

The zero only located the decimal point and is not significant

20.05 L

4 sig figs

1500 mg

4 sig figs

There is line over the final zero, so all digits are significant

0.0008 grams

1 sig fig

The zeros are only place holders. They are not significant

The End

Let’s practice!