**OBJECTIVE:**To learn to determine the number of significant figures in a calculated result.

Here we will learn to determine the number of significant figures in a calculation.

**Rules for Significant Figures**

1. Nonzero integers are always significant

- 1, 2, 3, 4, 5, 6, 7, 8, 9

- how many significant figures are in this measurement 1.234 cm
- Answer: 4

2. Three classes of zeros

a) Leading zeros are

**never counted as significant**

- Leading zeros are zeros that precedes all of the nonzero digits
- 0.0025mi. So how many significant figures are there in the measurement?
- Answer: 2 because the three zeros do not count since the are before the nonzero integers

**always count as significant figures.**

- Captive zeros are zeros that fall between nonzero digits
- 10.01 m/s. So how many significant figures are there in the measurement?
- Answer: 4 because the zeros is between two nonzero integers (1 and 4)

**only significant with a decimal point.**

- Trailing zeros are zeros at the
**right end**of the number - 1000. m; how many significant figures are in the measurement?
- Answer: 4 because of the decimal point behind the zero

3. Exact numbers

- calculation involved with counting has unlimited significant figures.
- Example: 10 people, 100 dollar, 3 apples, 8 molecules, and etc.
- Such numbers are called
**exact numbers.**They can be assumed to have an unlimited number of significant figures.

*Examples**How many significant figures are in the values shown below?*

*0.0101mg**123.020 mL**0.0100034 L**8182011. cal*

Answer

Answer

*3 - 0.0101mg**6 - 123.020 mL**6 - 0.0100034 L**7 - 8182011. cal*

**Video**